Thread: A list of sensors and how they work?

I am in the process of troubleshooting a crappy idle on my 99GTP and I wanted to check the cam position sensor but I have no idea what it is used for. I was wondering if a gm tech could possibly get a list of all the sensors used on our cars and a description of how they work and what they do? The possible make a sticky out of them for future troubleshooting?

I think that is an excellent idea. If someone takes up the challenge then I'll sticky it, if not I'll see what I can dig up.

I kind of tried searching the web, but I am not very good at it and didn't find what I want. The reason I said GM tech is because they have access to all of the GM info.

I think if we all collaborate together we can make said list, I'll start:

Cam Sensor- Hall effect? -used for injector timing
Crank sensor- Hall effect - two parts, one used for timing, other used for Tach and Traction control
Intake air Temp-thermistor- Used to help fueling by telling pcm intake air temp
Mass Air flow - ??? - sends a Frequency that equates to mg/sec of air the engine is ingesting, used for fueling
Throttle Position Sensor- Potentiometer - used to tell the computer how open the throttle plate is and also the speed it moves can be measured, used for transmission shifting and fueling
Manifold Absolute Pressure(MAP) - used to run engine during maf failure, also used to aid in fueling and judging engine load
Coolant Temp. Sensor- Used to tell the temp of the engine through the coolant, assists in fueling(by telling when it is warm enough for closed loop operation)

There are many more, and if any of above are wrong/ need to be erdited please let me know

Ok, now that 02BueGT gave that list what I want to know now is what happens when the cam sensor fails or what should happen when unplugged.

Originally Posted by Andrew_99GTP

Ok, now that 02BueGT gave that list what I want to know now is what happens when the cam sensor fails or what should happen when unplugged.

If the cam sensor fails, most times you will get a SES light. But not always. But if it does fail, you will probably experience bad timing.

But...I don't see this going bad very often. So I highly doubt this is your problem.

Post up your symptoms and we will see if we can help you.

I will post a thread in the L67 section.

Here is a little information on a Cam Sensor:


The Hall-Effect Sensor

Originally Posted by CT Tech

Remove the Mass airflow sensor and GENTLY clean the heated wires with a can of carb, brake or MAF cleaner. I have seen a lot of dirty MAF's make a car run really funny. You will need a tamper proof torx to remove the sensor.

I would think that brake and carb cleaner will damage the MAF. Best to use plastic-safe throttle body cleaner, or electronics cleaner with NO lanolin.

MAF: Works by a pair of thermistors. One is heated, one is not. The MAF calculates air flow by how the heated element is cooled to ambient by air flow, and then does the math.

TPS: Analog 5v potentiometer.

MAP: Analog 5v pressure sensing, most likely by a strain gauge.

ABS: Also Hall-effect or FET devices that pulse a signal to the EBTCM as the magnetic reluctor wheel in the hub rotates.

IAT: Not a sensor, but is a motor-driven valve that regulates idle air. When cleaning, be sure NOT to move the pintle, or damage can result. I clean mine with TB cleaner and a LOT of Q-tips to clean the valve seat.

Most engine pressure and temp sensors are analog thermistors referenced to ground. The coolant temp sender is actually 2 thermistors in one package. One sends to the PCM, the other to the instrument cluster.

I think the low coolant and low oil senders are either resistance to ground through the fluid, or proximity sensors.