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Lambda, Lambda, Lamba: Understanding Oxygen Sensors
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By Counterman
The wheel bearings are the backbone of the vehicle suspension. They support the weight of the vehicle, help to keep the wheels in alignment and allow the wheels to rotate with as little friction as possible. But wheel bearings can’t do their job without a strong mounting point, and that’s the knuckle.
What Is the Knuckle?
The knuckle, also known as the spindle, is the suspension component that houses the wheel bearing, and the connection between the wheel and the suspension system. In the past, knuckles typically were made of steel, but today they’re more commonly made of aluminum or another lightweight alloy to save weight.
On the front of the vehicle, the knuckle will pivot on upper and lower pivot points as the driver turns the steering wheel, changing the direction the vehicle is traveling in. In the rear suspension, the knuckle won’t pivot, but instead will travel up and down. Any time you’re removing or replacing a wheel bearing, ball joint, tie-rod end or control arm, you’ll be working on a knuckle.
Since the wheel bearings and the knuckles work together, sometimes it will make more sense to replace them together. This type of assembly is referred to as a “loaded knuckle.” Why would a customer decide to install a loaded knuckle? In most cases, it comes down to one of two reasons: damage or time.
What Can Damage a Knuckle?
They can be damaged during a crash or a collision, or from violently striking a curb or a deep pothole. This type of damage can change the geometry of the suspension, causing a crooked steering wheel, wandering steering feel while travelling straight, or steering bind. If left alone long enough, it even can result in abnormal tire wear down the road.
A knuckle also can be damaged due to a failed CV axle or wheel bearing. In this case, I’m talking about a scenario in which a driver ignores the grinding, metal-on-metal noises from a failing wheel bearing, and continues to drive for a long, long time. I’ve seen this exact scenario in the shop before, and it usually isn’t pretty. Eventually, the wheel-bearing bore becomes deformed thanks to the added stress, and the entire knuckle is only good for scrap.
There’s one more thing that could damage a knuckle: overtightening a ball joint or tie-rod end. Ball joints and tie-rod ends usually feature a tapered seat, which becomes tighter as the fastener is tightened. In older knuckles that were made of steel, that tapered bore would hold up pretty well, even if the fastener was a bit overtightened. But the modern aluminum or alloy knuckles are much softer, and they’re susceptible to damage from over-tightening. If the joint is tightened down but it’s still loose inside the tapered bore, the bore is damaged and the entire knuckle will need to be replaced.
What About Time?
So, we know why a customer might replace a damaged knuckle, but what does time have to do with it? That’s easy: Time is money. This applies to both DIY and DIFM customers. DIY customers are trying to get their vehicle fixed and back on the road as quickly as possible, especially if it’s their one and only vehicle. DIFM customers are trying to maximize their efficiency, and keep the shop running smoothly. In either case, if the customer runs into trouble, the results can be costly.
This is especially prevalent with press-in wheel bearings. This type of bearing is quite labor-intensive to remove and replace. After years of exposure to road debris, grit and salt, they can become stuck in place inside the knuckle. In extreme cases, it could take more time and labor to remove and replace a press-in bearing versus simply replacing the whole thing with a loaded knuckle.
On vehicles with aluminum knuckles, you may find that corrosion will form around a pinch bolt, axle nut or snap ring. This corrosion can make it extremely difficult, if not impossible, to remove that fastener. At some point, it makes more sense from a time and money standpoint to simply replace the entire knuckle, rather than get bogged down trying to remove a stubborn fastener.
Advantages of Loaded Knuckles
First and foremost, the nicest thing about a loaded knuckle is that it comes to you pre-pressed, so there’s no need to press out the old bearing, clean everything up and press in the new bearing. There’s no second-guessing if you set the bearing or the hub to the correct depth, or if you inadvertently damaged something by applying too much force with the shop press. That is a huge advantage to the DIY customer who might not have the necessary tools for this type of repair. It’s also helpful to the DIFM customer as it allows them to manage their time much more efficiently.
Customers might think that they can save a little bit of money by only replacing a wheel bearing and reusing the steering knuckle. But those savings can go right out the window if they run into unforeseen troubles during the repair. If they end up damaging other components, or they spend more time than expected simply trying to remove the old bearing, it can spell disaster. DIY customers can end up being without their vehicle for longer than anticipated, and DIFM customers can lose out on other business if the vehicle is stuck on a lift for longer than anticipated.
Replacing the entire knuckle and bearing assembly at the same time reduces the likelihood of a customer comeback, and increases the chances of the repair being completed correctly the first time. Installing a loaded knuckle can reduce installation time by up to 75% depending on the application. Just like a loaded strut, a loaded knuckle can help to take the hassle and guesswork out of a potentially troublesome repair.
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By Counterman
As modern cars and light trucks continue to grow in complexity, their maintenance needs are changing. Component failures that were commonplace just a decade or two ago are becoming much less common today.
An example of this is the throttle-position sensor (TPS). This small plastic sensor would be mounted on the throttle body, usually on the opposite of the throttle cable. The TPS was used to tell the engine control unit (ECU) what angle the throttle body was being opened to by the driver, and the ECU would adjust the fuel as needed based on this data as well as other inputs.
A faulty TPS reading can cause a number of drivability concerns, including:
• Unexplained bucking or jerking of the engine
• Surging engine idle
• Engine stalling, stumbling or hesitation
These sensors were rather inexpensive and usually pretty easy to replace. They didn’t fail too often, but I can remember having to replace them on a few of my own vehicles, as well as some customer vehicles. So what happened to throttle-position sensors, and why don’t we see them as often today?
Throttle-By-Wire
Throttle-by-wire technology has been called by many names, but it operates on a simple principle – an electronic throttle body is used to meter the air entering the engine. This electronic throttle body is controlled by the ECU based on a number of inputs including accelerator-pedal position, mass airflow, manifold air pressure, wheel speed and more. But the important thing to understand is that there is no longer a mechanical link between the accelerator pedal under the dashboard and the throttle body on the engine. So why is this important?
By decoupling the accelerator pedal from the throttle body, automakers are able to precisely control the throttle angle in all operating conditions to maximize throttle response and traction, reduce emissions and improve fuel economy. Throttle-by-wire systems are able to maximize the benefits of variable-valve timing and direct fuel injection by precisely controlling how much air is introduced to the engine.
With the advent of throttle-by-wire systems, we’ve seen a change in how the ECU measures the throttle position. The TPS still is being used today, but it’s now incorporated into the electronic throttle body. In fact, some electronic throttle bodies may contain more than one TPS. By using multiple sensors, the ECU can monitor and compare both sensor inputs. Redundancy in electronic systems can be a very good thing.
We’ll talk more about the pros and cons of throttle-by-wire a little bit later, but the fact that the TPS is now incorporated into the electronic throttle body can be a big drawback down the road. You see, it means that the system is now less serviceable than it was in the past. If a TPS failed on a cable-driven throttle body, you could replace the sensor for around $30 to $40 and be back on the road. If a TPS fails inside an electronic throttle body, now you have to replace the entire unit, and that could cost hundreds of dollars.
Then, after the electronic throttle body has been replaced, you’ll need to perform a “relearn procedure” so the ECU can learn how the new throttle body reacts to input, and where the internal mechanical stops are located. Failing to perform this critical step can cause a number of drivability concerns, and a costly customer comeback.
There has been a trend in the automotive space for quite some time now where components are becoming more and more “modular.” When I say “modular,” I really mean “pre-assembled.” After all, vehicles are engineered to go down the assembly line as fast as possible. They’re not engineered to be easy to work on. So it makes sense that automakers would get creative with incorporating certain components together into a modular assembly that can be installed more quickly. Of course, the major drawback with this idea is that the replacement costs are increased, and that cost will eventually fall onto the vehicle owner once the warranty period expires.
Advantages & Disadvantages of Throttle-By-Wire
Throttle-by-wire systems offer a number of advantages. They contain fewer moving parts, so that means less maintenance and lower overall vehicle weight. Their precision allows for improved fuel economy and reduced tailpipe emissions, as well as a better overall driving experience for the typical driver. Finally, the throttle body can be used to help the traction or stability control regain vehicle control.
These systems also have a few drawbacks. They’re more expensive to develop, manufacture and replace. They’re more complex due to the wiring and electronic control units that are used. Some drivers may complain about a time delay or “lag” in engine response after they change their accelerator-pedal input.
Finally, they’re harder to service for technicians. Sure, there aren’t any cables or linkage points to grease or maintain, but the real difficulty lies in the electronic controls. Complex wiring and communication systems are needed in order to control the electronic throttle body and related systems. There also are special procedures that must be followed whenever servicing the electronic throttle body. If an electronic throttle body is replaced, the relearn procedure must be performed. This has a profound effect on engine performance, drivability and idle quality.
If you find yourself selling a replacement electronic throttle body to a customer, there are a few questions you should be asking. Do they have a scan tool that’s capable of bi-directional control? A simple code reader won’t work here. They need the real thing in order to relearn the new electronic throttle body. Many electronic throttle bodies are installed in plastic intake manifolds, so it’s a good idea to sell them a new throttle-body seal as well. Finally, it’s a good idea to check with the customer to see if they’ve inspected the wiring harness and connections for any signs of rubbing, fraying or other issues. These sorts of problems can come back to bite them later on down the road.
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By NAPA
Engine coolant keeps the waste heat of the combustion process at bay. There’s no denying the importance coolant plays in keeping an engine running, but how do you know when it needs to be changed? But also to make sure your coolant is doing its job it needs to be monitored by a coolant sensor. Let’s look at how to test engine coolant, how to pressure test a cooling system, and equally important how to test coolant temp sensor operation.
Why Test Engine Coolant?
Your engine coolant is part of an enclosed system, but that system consists of many components of varying materials. Over time under the stress of extreme heat exposure the coolant loses some of its ability to control and conduct those temperatures. There are also parts of the cooling system that can corrode internally leaving tiny rust flakes that act like silty mud. There are all reasons why your engine coolant needs to be tested and periodically replaced when it has reached the end of its service life. But you need to test not only for the right coolant mixture ratio, but also the chemical composition of the coolant.
Testing Engine Coolant Ratio link hidden, please login to view
The easiest way to test coolant mixing ratio with an
link hidden, please login to viewr. This neat little device tests the specific gravity of the coolant using either little colored floating balls or a swing arm. The balls and swing arm are calibrated to float at different levels based on the specific gravity of the coolant. Simply draw coolant into the antifreeze tester and compare the results to the included chart. Typically on a floating ball type tester the higher the concentration of ethylene glycol, the more balls that float. You can then estimate the freezing point of the coolant and how well you are protected against the cold. Just be aware that there are different testers for propylene glycol and ethylene glycol, so choose a tester that matches what is used in your cooling system. For a more accurate measurement of your coolant’s freezing point you can use a refractometer. There are
link hidden, please login to viewand link hidden, please login to viewrefractometers but they both work on the same idea. Simply place a few sample drops of coolant in the tool. For the analog refractometer you then look through the eyepiece and read the inside gauge. For the digital refractometer you just have to push a button and the reading will be displayed on the screen. You will need to read the instructions and be familiar with the tool to understand what the results of each one means to the specific gravity of your coolant. Testing Engine Coolant Condition
As mentioned earlier your coolant can actually degrade over time. Luckily a simple
link hidden, please login to viewcan give you a glimpse of what is in your coolant. When the engine is cool and depressurized (never work on a hot engine’s cooling system) just remove the radiator cap and dip in a testing strip. Make sure to read the directions included with the testing strip to make sure you get a good reading. Most test strips can tell you the pH level, nitrate concentration level, and liquid freeze point. If any of these readings are out of specification, it is time for a link hidden, please login to viewand refill. How To Test A Coolant Temp Sensor
Knowing how to test coolant temp sensor output is a bit more technical. You will need a multimeter to read the resistance of the coolant temp sensor during the test. You will also need to remove the coolant temp sensor from your vehicle, so refer to a repair manual for the specific procedure. For sensor range testing you will need a container of ice water and a container of boiling water. Finally you need the factory sensor range specifications (usually found in the repair manual) along with a pen and paper to take notes.
Once you have the sensor out of the vehicle attach it to the connections on the multimeter. Most sensors have two connections and since you are testing resistance, it does not matter which order is used. If your sensor has more than two connections refer to a vehicle wiring diagram to find the ground connection and the voltage input connection.
You will be testing engine coolant temperature sensor resistance output in cold water and hot water, then comparing the two readings to the factory specification found in your repair manual. Check the temperature of the ice water to make sure it is as close to freezing as possible (32 degrees F or 0 degrees C). Set the voltmeter to the 20,000 ohm range. Dip the tip of the sensor in the cold water and observe the reading on the multimeter. When the reading stops changing, write it down on the paper as the cold reading. Repeat the same process with the boiling water, being careful to hold the sensor with tongs or similar tool to reduce the chance of touching the boiling water. Write down the hot temperature reading from the multimeter.
Now you can compare the two voltage readings to the factory sensor specifications. If the readings are not within specifications the sensor is bad and should be replaced. Now that you know the steps for how to test an engine coolant temperature sensor, you can decide if it is worth your time or if the sensor is cheap enough to just replace it and move on.
How To Pressure Test A Coolant System
Luckily learning how to pressure test coolant system components is pretty easy. You will need an
link hidden, please login to view which looks like a bicycle tire pump attached to a universal radiator cap. Start with a cool engine (never work on a hot engine cooling system under pressure). Remove the radiator cap or coolant reservoir cap if so equipped. Attach the pressure tester to the same place where you just removed the radiator cap or reservoir cap. The pressure tester may have a universal rubber fitting or come with an array of adapters to connect with your particular cooling system. Now use the pump to add pressurized air to the cooling system. Watch the pressure gauge on the pressure tester and add roughly 15 psi of pressure (but no more than that). The pressure gauge should hold steady indicating no leaks. If the pressure gauge goes down or does not register any pressure, double check your pressure tester connection just in case. If the system will not hold pressure, you will need to repair the leak. You can use link hidden, please login to view to help locate the leak if it is not easily apparent. Check out all the
link hidden, please login to view available on link hidden, please login to view or trust one of our 17,000 link hidden, please login to view for routine maintenance and repairs. For more information on how to test engine coolant sensor output and other cooling system parts, chat with a knowledgeable expert at your link hidden, please login to view. The post
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By Counterman
Alligator sens.it RS universal TPMS sensors now cover the 2020-2021 Ford Bronco.
“This vehicle has hit the market by storm and Alligator is proud to offer service for this impressive new SUV,” Alligator said in a news release.
The all-terrain Bronco is another addition to the expanding list of Ford vehicles that can automatically learn and detect TPMS sensors once installed into each wheel assembly, or if rotating tires at regular intervals.
Alligator offers these instructions: Simply install the new Alligator sens.it RS universal TPMS sensors, then begin driving the SUV, and the system will register the new IDs automatically while driving. Based on the instruction manual, make sure to park the vehicle the required amount of time for the TPMS system to enter into relearn mode (usually 20 minutes).
The Alligator sens.it RS universal TPMS sensor also supports location detection, so when rotating tires, there’s no need to reset the system manually. Simply follow the same procedure as auto-learning and the display will show the new tire locations on the dash after driving for a few minutes.
“By continuing to use Alligator sens.it RS universal TPMS sensors, shops can ensure they are working with a part that supports the full range of OE features, which helps make the job easier, reduces unnecessary downtime in the bay for TPMS learning or general sensor issues, helps the bottom line and, most importantly, keeps customers happy and coming back,” the company said. “When replacing OEM sensors with aftermarket sensors, rest assured that RS Series TPMS sensors from Alligator will provide all the functionality your car delivers. Regardless of the tool you use to program your Alligator TPMS sensors, this new application should be available for programming after you complete the latest update.”
Alligator is a brand of
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By Counterman
Who remembers having your driving instructor tell you to “pump the brakes” when stopping on slippery roads? If you raised your hand, congratulations – you’re over the hill like me!
The purpose of pumping the brakes was to humanly perform what an ABS does. You apply the brakes just to the point where the tires begin to slip on the road surface, then release and reapply pressure as quickly as possible. You simply do this over and over again, all in a split second. And if it’s an emergency, you calmly steer around the danger as adrenaline rushes through your veins and your heart rate skyrockets. No problem, right?
Well, I think you can see the problem. And, what if one tire is on ice and the other isn’t? There goes the steering, and there’s no fancy footwork that can overcome that.
So, what was the solution? Antilock braking systems (ABS). When they were first developed, the intention was that a driver could maintain directional control of a vehicle under extreme braking (when a wheel locks up, steering control is lost). The fact that ABS stops a vehicle quicker in a straight line (though not an unexpected result) was just a bonus.
ABS Operation
ABS initially was a dedicated braking system, but the signals from the wheel-speed sensors (WSS) quickly proved useful for traction- and stability-control systems, and on some vehicles the signals also are utilized by the powertrain control module for other functions. It can seem complicated, but for the practicality of parts and service, we can leave that end of it to the engineers who design the systems.
Functionally, ABS is one of the easier systems to understand, and we can break it down into three main areas: the WSS, the ABS control module and the ABS modulator.
Each WSS generates a signal proportionate to wheel speed and sends that signal to the ABS control module. The WSS works in conjunction with a reluctor wheel, which is a toothed wheel that is fixed on a component rotating at wheel speed. This allows the WSS to generate a signal through electromagnetic or Hall-effect principles.
The ABS control module is the computer that monitors the WSS signals, decides what to do and when, and sends output commands to the ABS modulator.
The ABS modulator is the hydraulic unit of the ABS system that contains the ABS pump and valving. The regular state of the valves allows hydraulic pressure from the brake master cylinder to pass through for normal braking. If, during braking, the ABS control module receives a signal from one or more WSS that indicates a wheel is losing traction (locking up), it sends a signal to the ABS modulator, and the valve for that given wheel closes to prevent additional hydraulic pressure from being applied.
If the wheel continues to lose traction, the valve then will release the pressure on that given wheel. The pressure is released to prevent wheel lock-up, but the pressure must be reapplied immediately for proper braking and steering control. This is when the ABS pump turns on to create the necessary hydraulic pressure for this to happen. Not too bad so far, right?
ABS Repair and Diagnosis
When it comes to repair, the vast majority of the time, real-world ABS problems are caused by nothing more than the fact that one or more of the wheel-speed signals received by the ABS control module is incorrect. Depending on the nature of the errant signal, the ABS control module responds by either actuating ABS function when it is not required, or by storing a diagnostic trouble code (DTC) and turning on the ABS warning light.
Taking it one step further, the vast majority of errant wheel-speed signals are caused by either wiring issues such as a broken wire or resistance in a connector; a WSS that is not positioned properly to pick up the signal from the reluctor wheel; or, in some cases, a missing or damaged reluctor wheel. A WSS can go bad, of course, but it’s less common than a related mechanical or electrical issue that affects the ability of the sensor to get its signal to the ABS control module.
If you’re playing the role of technician and a customer is asking you to help with their self-diagnosis of an ABS issue, they’re not going to get anywhere without a scan tool. Luckily, there are some basic scan tools that have just the right functions. In the case of ABS, if you can view DTCs and wheel-speed data, you’re most likely going to have all you need. If there’s a DTC stored, this provides the initial information to begin diagnosis. For example, a DTC may be “RF wheel-speed sensor implausible signal.”
Wheel-speed data allows you to see the reported speed from each sensor. If everything is working correctly, you can watch the speed of each wheel as you slow down, and all four should read the same: 10, 9, 8, 7 … all the way down to zero, almost.
There’s a catch. For a long time, most wheel-speed sensors were considered “passive” sensors, which generated their own electrical signal when the vehicle was in motion. These sensors aren’t able to generate and send a signal below 3 or 4 mph, so seeing the reading drop off at low speeds is normal. But, when compared to the others, if one drops off earlier, then you have identified a problem area, and just need to determine why.
Whereas passive sensors generate their own signal, active sensors receive a reference voltage and work like a Hall-effect sensor, so they’re able to provide a wheel-speed reading all the way down to zero. This ability improves ABS performance at low speeds and has made them more common. Either way, wheel-speed data is the primary diagnostic focus for ABS systems.
Selling ABS Components
Scan Tools
If you stock basic scan tools and you offer one with ABS functions, borrow one and try it out. It’s fun to see the ABS data and see first-hand how you can relate it to ABS operation. Plus, when you’re talking to a customer, it gives you the upper hand in knowledge to sell them on one. It’s a good investment, because if they’re keeping and maintaining an older vehicle and there’s one problem now, there will be another down the road.
Electrical Repairs
Wiring problems are incredibly common, and it’s usually right down near the wheel. The ABS harness might have worn from age, but this isn’t too common. More often, something off the road has damaged it, or it wasn’t properly installed and rubbed against a wheel or other suspension component. The best practice is to always advise your customer to replace the sensor with a new harness (most sensors have an integrated harness that connects to the main harness just inside the wheel well). The reason is that any repair eventually will have an effect on circuit resistance, and like any computer-related circuit, even the slightest increase in resistance can cause a problem.
There always will be times when a customer will forego a sensor and opt for a repair, but this still is an opportunity to sell them the tools and supplies they might need – such as wire strippers/crimpers; extra wire; butt connectors; solder; a soldering gun; heat-shrink tubing; and electrical tape.
Using butt connectors to repair the harness is temporary at best. Although butt connectors are acceptable for some electrical repairs, in this case it introduces a rigid area into a harness that needs to flex due to suspension and steering movements. Each end of this rigid section is now more susceptible to breaking. The ideal repair – although still never considered “permanent” – is to solder a very small, short (approximately 1 mm) section of the wires, then seal the repair with heat-shrink tubing. The more precise you can be, the less rigidity you will introduce into the harness, and the longer it will last.
Wheel Bearings
Generally speaking, wheel bearings have nothing to do with ABS, but in some cases, the reluctor wheel is part of the wheel bearing. Some vehicles have press-in style wheel bearings that appear identical on both sides, but one side has a reluctor and one doesn’t. Pressing this style of wheel bearing in wrong is a common mistake, and with no reluctor wheel by the WSS, there is no way of generating a WSS signal.
Even on an older vehicle, when someone is replacing a wheel bearing, be sure to ask if it has ABS. It may or may not be relevant depending on the vehicle, but better to ask and avoid the potential for a problem. Along the same lines, if you sell a bearing that appears as if it could install either way and the vehicle has ABS, make sure to determine if it is indeed a bearing with an internal reluctor wheel.
On wheel-bearing/hub assemblies that are more common today than the press-in style, most of the time the ABS sensor comes with the assembly. Often the customer doesn’t notice the worn, loose wheel bearing until it affects the ABS sensor, and they may think the ABS sensor itself is the problem. If the ABS sensor is available separately, be sure and caution them that a bad wheel bearing may have caused the problem in the first place, and they should check it if they’re not sure.
CV Shafts
The same holds true here. Generally, a CV shaft has nothing to do with ABS, except that many of them have the reluctor ring on the outboard CV joint. Always ask if a car has ABS when ordering a CV shaft, just to make sure you get the right component. Since CV shafts often fit more than one application from the same manufacturer, it’s common for them to all be made with reluctor wheels simply to avoid the problem in the first place. If the car doesn’t have ABS or if the reluctor is in the wheel bearing, the reluctor on the CV joint does no harm or it can be removed.
Flush Brake Fluid
Brake-fluid flushes often are ignored, and while problems with ABS modulators are uncommon, when they do arise, it’s frequently because the brake fluid wasn’t flushed. It’s always a good service to recommend.
Tires
Why tires? If someone has installed the wrong-size tire in one location, guess what immediately changes? Wheel speed. I think you know
the rest.
Sensors
ABS sensors generally are easy to sell because we look them up by application and there are no other factors involved. You can take advantage of additional sales and save your customer time when sensors have to be removed during the course of another repair. Many sensors fit into a hole, and after a few years of driving, they might as well be welded in place. ABS sensors frequently need to be replaced simply because they’ve been destroyed during removal.
All in all, ABS isn’t too complicated, so you can be comfortable helping your customers understand how it works. Getting them all the right parts and giving them good advice is what brings them back.
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