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FRAM® Provides Next-Level Engine Protection for the Summer
Protect Your Fuel Tank and Pump With Delphi Technologies
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Auto Value, Bumper to Bumper Tech OTY Finalists Named
FRAM® Provides Next-Level Engine Protection for the Summer
Sponsored By BCA Bearings by NTN
Sponsored By Carter Fuel Systems
Sponsored By NGK Spark Plugs
AC Diagnostics: Troubleshooting Pressures and Temperatures
The most difficult AC complaints to resolve are the system blows warm, or the air is not as cold as it once was. The causes of the declining performance could be caused by a multitude of components and conditions. In a 45-minute webinar, the experts from Transtar AC will cover the possible causes of AC failure.
The training session will cover:
Speakers Andrew Markel, Director of Technical Content, ShopOwner Dennis Husband, ASE Certified Technician, Transtar AC
Sponsored By BCA Bearings by NTN
ShopOwner includes technical and management content and is free to download and read.
The knock sensor is not the only sensor responsible for detecting engine knock.
Throttle-by-wire systems proactively manage the air and fuel going into the combustion chamber.
Underhood Service targets repair shops that derive 50 percent or more of their revenue from the service and repair of under-the-hood systems. The expanding amount of knowledge and capital needed to keep up with technological advances has led these shop owners to concentrate on underhood systems, while also offering preventive maintenance services on most major vehicle systems. By subscribing, you’ll receive the ShopOwner digital edition magazine (12 times/year) featuring articles from Underhood Service and the Underhood Service eNewsletter (twice weekly). Access to digital editions, contests, news, and more are ready for you today!
Underhood Service targets repair shops that derive 50 percent or more of their revenue from the service and repair of under-the-hood systems. The expanding amount of knowledge and capital needed to keep up with technological advances has led these shop owners to concentrate on underhood systems, while also offering preventive maintenance services on most major vehicle systems. By subscribing, you’ll receive the ShopOwner digital edition magazine (12 times/year) featuring articles from Underhood Service and the Underhood Service eNewsletter (twice weekly). Access to digital editions, contests, news, and more are ready for you today!
ByUnderhood Service Staff Writers on Jul 15, 2022
High underhood temps, increased power demands and vibration can damage alternators or starters. Sponsored by ACDelco.
Don’t settle for “almost” - it matters where the engine is manufactured or remanufactured. Sponsored by ACDelco.
Brake pads are thoroughly developed to produce the best result. This video is sponsored by ZF Aftermarket.
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The knock sensor is not the only sensor responsible for detecting engine knock.
A knock sensor is a piezoelectric accelerometer that acts as a microphone on the engine. It converts vibrations into an alternating current (AC) signal. When the crystal inside the sensor is vibrated, it produces an AC voltage. The greater the vibration or shock, the higher the voltage and frequency.AdvertisementThe ECM can look at the output from the knock sensor and determine if something is going wrong in the combustion chamber and take action, like changing the ignition timing or adding fuel. The knock sensor is not the only sensor responsible for detecting engine knock. The ECM looks at the crank angle sensor data to determine at which cylinder the event is taking place and whether the crankshaft had a sudden change in speed. That way, the ECM can determine if the driver just hit a pothole, or if a knock occurred. It can also identify if the event happened before or after top dead center. Testing If you’re using a meter, set it to AC volts. If you are using a scope, make sure the AC filtering is turned off. If you are testing the sensor on the vehicle, you need to access the connector. Knock sensors have only two wires. Knock sensors are mounted on the block near the base of the cylinder head. On an inline engine, the sensor is easy to access. On V6 and V8 engines, the knock sensor might be in the valley of the engine under the intake manifold.AdvertisementThere are two schools of thought for testing. If the sensor is out in the open, you can use a blunt chisel and hammer and strike the area around the knock sensor. If the sensor is inaccessible, you can run the engine and pull the fuse for the fuel pump and let the engine stall. The lean conditions might produce an engine knock. But, this type of testing can be hard on an engine. Knock sensors rarely degrade; they typically fail and will not produce a signal no matter how hard you hit them. When you are looking at a meter, you will see a change of 0.06V when striking around the sensor. Using the min/max feature, you might see higher voltages. You can also check the amount of resistance across the sensor and verify the value with the service information. A scope can provide you with a better picture of what the sensor is doing, even while the engine is running.AdvertisementSome engine management systems will send out a brief bias voltage signal to check the condition of the circuit when the vehicle is started. If the circuit has higher-than-normal resistance due to corrosion or a bad connection, the voltage will drop, and a code will be set for low voltage. The ECM also knows what types of voltage the knock sensor should produce during startup and idle, and it will set a code if it does not see the correct value. If a knock sensor-related code is set, the ECM may use a more conservative fuel map or even limit engine loads and RPM. This is to protect the engine and safeguard against possible damage to the combustion chamber.
The ECM can look at the output from the knock sensor and determine if something is going wrong in the combustion chamber and take action, like changing the ignition timing or adding fuel.
The knock sensor is not the only sensor responsible for detecting engine knock. The ECM looks at the crank angle sensor data to determine at which cylinder the event is taking place and whether the crankshaft had a sudden change in speed. That way, the ECM can determine if the driver just hit a pothole, or if a knock occurred. It can also identify if the event happened before or after top dead center.
If you’re using a meter, set it to AC volts. If you are using a scope, make sure the AC filtering is turned off. If you are testing the sensor on the vehicle, you need to access the connector. Knock sensors have only two wires.
Knock sensors are mounted on the block near the base of the cylinder head. On an inline engine, the sensor is easy to access. On V6 and V8 engines, the knock sensor might be in the valley of the engine under the intake manifold.
There are two schools of thought for testing. If the sensor is out in the open, you can use a blunt chisel and hammer and strike the area around the knock sensor.
If the sensor is inaccessible, you can run the engine and pull the fuse for the fuel pump and let the engine stall. The lean conditions might produce an engine knock. But, this type of testing can be hard on an engine.
Knock sensors rarely degrade; they typically fail and will not produce a signal no matter how hard you hit them. When you are looking at a meter, you will see a change of 0.06V when striking around the sensor. Using the min/max feature, you might see higher voltages. You can also check the amount of resistance across the sensor and verify the value with the service information. A scope can provide you with a better picture of what the sensor is doing, even while the engine is running.
Some engine management systems will send out a brief bias voltage signal to check the condition of the circuit when the vehicle is started. If the circuit has higher-than-normal resistance due to corrosion or a bad connection, the voltage will drop, and a code will be set for low voltage. The ECM also knows what types of voltage the knock sensor should produce during startup and idle, and it will set a code if it does not see the correct value.
If a knock sensor-related code is set, the ECM may use a more conservative fuel map or even limit engine loads and RPM. This is to protect the engine and safeguard against possible damage to the combustion chamber.
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Technical resources to help diagnose and repair engine-related service issues.