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By Counterman
Wheel-speed sensors aren’t new to any of us. They’ve been around for years, and their initial purpose was to provide wheel-speed data to the control unit for the antilock braking system (ABS). Because of this, they’re often called ABS sensors.
On today’s vehicles, however, the ABS isn’t the only system that utilizes wheel-speed data. Multiple safety and comfort systems such as advanced driver-assistance systems (ADAS), traction control and parallel-parking assist rely on wheel-speed data to function properly.
At a glance, all wheel-speed sensors may appear to be the same. But there are two different types: passive and active. Essentially, both have the same job of providing wheel-speed data to various control units, but they differ in how they do it and how well they do it.
Passive Wheel-Speed Sensors
Passive wheel-speed sensors are constructed with a permanent magnet and fine copper wire and generate a magnetic field. They operate in conjunction with a toothed metal ring, called a tone ring, which rotates at wheel speed. As the teeth of the tone ring pass through the magnetic field, it causes the polarity of the sensor to change and generates an alternating-current (AC) signal.
This AC signal is sent to the ABS control unit, which in turn must interpret it to determine when ABS operation is required. While passive sensors have been effective for many years, they have several drawbacks. A common problem with these and any type of permanent magnet sensor is limited operation at low speeds. In the case of wheel speed, a passive sensor is only able to generate a signal at approximately four miles per hour and higher.
They also do not generate a signal in reverse, and the gap between the sensor and the teeth on the tone ring is critical. Even the slightest amount of rust buildup underneath one of these sensors can cause erratic operation and unwanted activation of the ABS under braking. In addition, the magnetic field of these sensors can attract fine metal particles over time, which further inhibit proper system operation.
Active Wheel-Speed Sensors
The AC signal generated by a passive wheel-speed sensor is an analog wave, or a continuous smooth waveform. An active wheel-speed sensor, on the other hand, produces a digital signal, which is viewed as a square waveform. A digital signal is a very accurate and precise on/off signal.
Many of the other control units associated with today’s advanced systems rely on this type of precision for proper system operation. In addition to the accuracy, an active wheel-speed sensor can read wheel speed practically to zero mph, which is critical data for modern traction-control and driver-assistance systems, and some also can detect reverse wheel rotation.
Active wheel-speed sensors require power to operate, whereas passive units do not. There are two types of active wheel-speed sensors: a Hall-effect sensor and a magneto-resistive sensor. A Hall-effect sensor requires either a toothed or magnetic ring to generate a voltage signal, whereas a magneto-resistive sensor utilizes a slightly different type of encoder ring, allowing it to determine direction of wheel rotation.
The most important part about these sensors is knowing that they’re different. Visually they look the same, but functionally they’re not interchangeable. Some makes and models that are traditionally thought of as the “same” vehicle with different badging can utilize different sensors, even for the same model year.
When it’s all said and done, active wheel-speed sensors are necessary for today’s advanced systems, but regardless, all wheel-speed sensors take a lot of abuse, simply due to their location. Any time there’s a problem indicating a bad wheel-speed sensor, all components must be taken into account including the sensor itself, as well as the wheel bearing and CV joint, which may house or support the tone ring or encoder wheel necessary for sensor operation.
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By Counterman
Continental has added eight new part numbers to its line of OEM knock sensors.
The sensors are the same part that the vehicle manufacturer uses and deliver the exact fit, form and function as the original part, ensuring an easy installation and long service life, according to Continental.
The eight new part numbers provide application coverage for some of the most popular domestic, European and Asian makes and models on the road today. The expanded line covers Chrysler, Dodge, Ford, Infiniti, Jeep, Lincoln, Mercedes-Benz, Mercury, Nissan and Ram models ranging from 2000 to 2023. The new sensors provide coverage for 28.8 million vehicles in operation (VIO) in the United States and 2.4 million vehicles in Canada.
“Our newly expanded line was developed to meet the growing need for reliable knock sensors on some of the most common vehicles on the road today,” noted Brendan Bachant, Continental product manager for engine management and fuel. “The original sensors can be prone to failure due to mechanical damage, excessive vibration, high engine temperatures, and corrosion. Continental has made these OEM sensors available to the aftermarket so that professional technicians can easily and confidently service the most common vehicles in the shop, like the Ford F-150 and Explorer, the Jeep Wrangler and the Nissan Maxima and Altima. Technicians can be confident when choosing the Continental knock sensor that they will avoid comebacks.”
Knock sensors are designed to detect engine ping caused by pre-ignition and relay the information to the electronic control unit to adjust engine timing and help keep the engine running smoothly. These sensors are an ideal repair for a rough-running engine with a timing and knock-sensor fault code and will help shops to restore the performance of their customers’ vehicles to OE specifications, according to Continental.
Continental knock sensors are built in ISO-certified facilities to deliver the highest level of dependability, the company noted.
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By Counterman
Older vehicles with carburetors and distributors didn’t need to know the position of the crankshaft or the camshaft. Timing was fixed, and the timing could easily be set, as long as the technician could line up top-dead-center on cylinder No. 1 and line up the mark on the crankshaft pulley. But this was back before fuel injection was standard, and today’s engines are a lot more advanced than those older carbureted engines.
Today, the engine control unit (ECU) needs to monitor the exact position of the crankshaft and the camshaft (or camshafts) at all times. This is accomplished through the use of camshaft position sensors and crankshaft position sensors. The ECU uses the information from these sensors to adjust the timing of the valves, fuel injectors and ignition coils.
Put simply, the ECU cannot accurately calculate ignition timing and VVT parameters without knowing precisely where the crankshaft and camshaft both are at any given moment. These sensors are critical to ensuring maximum efficiency, power and torque during all operating conditions.
But what happens when these sensors start to fail, or fail completely? Individual experiences may vary, but you can expect to see symptoms such as:
• Rough or erratic idle
• Crank/no-start
• Loss of power
• Illuminated “Check Engine” light
A faulty crankshaft position sensor can cause the engine to crank but not start, also known as a “crank/no-start.” The engine may be able to run without a signal from the camshaft position sensor, but it may trigger a reduced-power or “limp-home” mode.
If your customer checks the ECU for DTCs and they find P0011 (camshaft position bank 1) or P0021 (camshaft position bank 2), their first step should be to check the engine oil. That’s right, check the engine-oil level, and top off as needed. Dirty oil, or a low oil level, can wreak havoc with the VVT components and cause these DTCs to set. In fact, the most common cause for VVT-system issues seems to stem from a lack of basic maintenance. Old, dirty oil can carry sludge and debris that can plug up the tiny passageways for the VVT actuators and other components.
The relationship between the camshaft and crankshaft is critical in today’s VVT systems. If the camshaft sensor or crankshaft sensor starts to produce a faulty signal, the VVT-system performance will suffer. Of course, a loose or stretched timing chain or timing belt, or a worn timing guide or tensioner, also can negatively affect the VVT system.
What causes a crankshaft or camshaft sensor to fail? While every electronic component under the hood will fail eventually, camshaft sensors and crankshaft sensors can fail prematurely if they’re subjected to extreme temperatures (i.e. engine overheating) and/or contamination (metal shavings or debris carried by the oil, or contamination from an outside source under the hood).
So, now we know a bit more about the relationship between the camshaft position sensors and crankshaft position sensors and modern-day engine management. These days it’s safe to say that every vehicle system is sharing data, so they all depend on one another to operate at their best. In this case, data from the crankshaft sensor and camshaft sensor allows the ECU to optimize the timing of the valves, fuel injectors and the ignition coils. This continuous optimization enables modern engines to run with far greater efficiency than ever before.
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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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