Testing the camshaft position sensor and/or diagnostic trouble code (DTC) P0341, on your 3.8L V6 equipped GM car or mini-van, is an easy test that can be done using only a multimeter. No scan tool is needed for this test! Now, since the cam sensor can not be tested with a simple resistance test (Ohms), the test I'm gonna' show you is a dynamic test done by cranking the engine by hand.
If you need to know if this camshaft position sensor test applies to your specific 3.8L GM vehicle, take a look at the ‘Applies To:’ box on the right and scroll with the arrow buttons to see all of the applications.
Here are the contents of this article at a quick glance:
- Symptoms of a BAD Cam Sensor.
- Tools You'll Need to Test the Cam Sensor.
- How the Cam (CMP) Sensor Works.
- How to Read the CMP Images.
- CMP TEST 1: Cam Signal Test.
- CMP TEST 2: Power Circuit.
- CMP TEST 3: Ground Circuit.
- CMP TEST 4: Removing the CMP Sensor.
- Where to Buy the Cam Sensor and Save.
- Related Test Articles.
You can find this tutorial in Spanish here: Cómo Probar: Sensor de la Posición del Árbol de Levas (GM 3.8L) (at: autotecnico-online.com).
Symptoms of a BAD Cam Sensor
The one symptom you're gonna' experience is the check engine light (CEL) shining nice and bright to let you know that there's a problem.
You'll also see one or several of the following symptoms when the cam sensor fails:
- Diagnostic trouble code: P0341: Cam Sensor Circuit Performance.
- Poor gas mileage.
- Idle rough at start up and engine may stumble and stall.
The one thing you need to keep in mind is that a cam sensor failure will not keep your car from starting.
Tools You'll Need to Test the Cam Sensor
Although it sucks that you're having a cam sensor issue with your 3.8L equipped vehicle, the cool thing is that you don't need any expensive tools to test it. You don't even need to use a scan tool.
Tools You'll Need:
- You can use a digital multimeter or an analog multimeter although the digital one is the preferred one.
- If you don't have a multimeter or need to upgrade yours, check out my recommendation here: Buying a Digital Multimeter for Automotive Diagnostic Testing (at: easyautodiagnostics.com).
- Fack stands
- 1/2 inch ratchet wrench and the appropriate socket to turn the crankshaft pulley bolt.
If possible, I recommend having a helper to help you.
How the Cam (CMP) Sensor Works
The camshaft position sensor, on your 3.8L V6 GM engine, is a three-wire Hall Effect Type sensor. So, for it to work, it's gonna' need an external power supply and a path to ground (for this power).
- When you turn on the Key and crank the engine:
- Power and ground come from the ignition control module.
- Power is in the form of 10 Volts, and the circuit (wire) that feeds this power also feeds the crankshaft position sensor.
- The camshaft position sensor also gets 5 to 7 Volts DC on the cam position signal circuit. This voltage also comes from the ignition control module (ICM).
- As the engine cranks:
- The camshaft position (CMP) sensor is activated by a magnet on the camshaft gear (this magnet is known as the camshaft position sensor interrupter).
- As the cam gear turns and this magnet passes the camshaft position (CMP) sensor, it activates the cam sensor.
- Activation of the cam sensor (by the CMP interrupter) means that the sensor pulls down the voltage, supplied to it on the cam signal circuit, to 0 Volts.
- What this translates into is an On/Off signal that the ignition module (and the PCM) translate into a camshaft position sensor signal.
OK, as you may have already deduced, from the info above, the camshaft position sensor's wires do not connect directly to the fuel injection computer. Instead, they run directly to the ignition control module (ICM) and the ICM then sends the cam signal to the PCM on circuit F (of the ignition control module's connector).