How To Test Camshaft Position Sensor (2002-2005 4.2L Chevrolet Trailblazer)

TEST 2: Making Sure The Camshaft Position Sensor Is Getting Power

If in the previous test the camshaft position sensor did not produce an ON/OFF voltage signal then there's a good chance that it might be missing power or Ground.

In this test section we're going to make sure that your Chevrolet Trailblazer or GMC Envoy's fuel injection computer is supplying 10 to 12 Volts to the camshaft position sensor.

Power is supplied by the wire labeled with the letter A in the photo above. This is the red (RED) wire of the connector.

If power is being supplied to the camshaft position sensor then our next step is to make sure that it's getting Ground.

We'll test that the sensor is getting power by doing a simple multimeter voltage test.

These are the test steps:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Disconnect the camshaft position sensor from its electrical connector.

3. 3

   Connect the red multimeter test lead to the wire identified with the letter A.

4. 4

   Connect the black multimeter test lead to the battery negative (-) terminal.

5. 5

   Turn the key ON but don't crank or start the engine. This will power up the connector.

6. 6

   Your multimeter should give you a reading of 10 to 12 Volts DC.

Let's examine your test results:

CASE 1: The multimeter registered 10-12 Volts. This confirms that the camshaft position sensor is getting power from your TrailBlazer or Envoy's fuel injection computer.

The next thing to do, is to check that the camshaft position sensor is getting Ground from the computer too. For this test go to: TEST 3: Making Sure The Camshaft Position Sensor Is Getting Ground.

CASE 2: The multimeter DID NOT register 10-12 Volts. The camshaft position sensor will not create a cam position signal without power.

With this test result, you have now eliminated the camshaft position sensor itself as the cause of the camshaft position sensor code (P0340 Camshaft Position Sensor Circuit or P0341 Camshaft Position Sensor Performance). Solving this lack of 12 Volts, to the cam sensor will get it back to working again.

TEST 3: Making Sure The Camshaft Position Sensor Is Getting Ground

If you've reached this point you have confirmed that:

• That the camshaft position sensor is not producing an ON/OFF signal as you turned the engine by hand.
• That the camshaft position sensor is getting power from the fuel injection computer.

For our last test we are going to make sure that the sensor is getting Ground.

Ground is supplied by the wire labeled with the letter C in the photo above. This wire is the pink with black stripe (PNK/BLK) wire of the connector.

Testing for the presence of this Ground is done with a simple multimeter voltage test.

IMPORTANT: As mentioned before the fuel injection computer is the component that supplies this Ground to the camshaft position sensor. For this reason you need to be careful not to apply 12 Volts (battery power) to this wire or you're going to fry the fuel injection computer. The multimeter voltage test that I am recommending is a safe way of making sure that this Ground is present.

These are the test steps:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Disconnect the camshaft position sensor from its electrical connector.

3. 3

   Connect the black multimeter test lead to the wire identified with the letter C.

4. 4

   Connect the red multimeter test lead to the battery positive (+) terminal.

5. 5

   Turn the key ON but don't crank or start the engine. This will power up the fuel injection computer.

6. 6

   Your multimeter should give you a reading of 10 to 12 Volts DC.

Let's examine your test results:

CASE 1: Your multimeter registered 12 Volts DC. This test result lets you know that the fuel injection computer is providing Ground for the camshaft position sensor.

You can conclude that your TrailBlazer or Envoy's camshaft position sensor is defective only if you have:

• Confirmed that the sensor is not producing an ON/OFF voltage signal.
• Confirmed that the sensor is getting power.
• Confirmed that the sensor is getting Ground.

CASE 2: Your multimeter DID NOT register 12 Volts DC. The camshaft position sensor will not create a cam position signal without Ground.

With this test result, you have now eliminated the camshaft position sensor itself as the cause of the camshaft position sensor code (P0340 Camshaft Position Sensor Circuit or P0341 Camshaft Position Sensor Performance). Solving this lack of Ground to the cam sensor will get it back to working again.

More GM 4.2L Test Tutorials

I've written quite a few tutorials for the 4.2L Chevrolet TrailBlazer And GMC Envoy. You can find them here: GM 4.2L Index Of Articles.

Here's a sample of the tutorials you'll find there:

• How To Test For A Blown Head Gasket (2002-2009 4.2L Chevrolet TrailBlazer).
• How To Test The MAP Sensor (2002-2007 4.2L Chevrolet Trailblazer).
• How Often Should I Replace The Spark Plugs? (2002-2009 4.2L Chevrolet TrailBlazer).
• How To Test Engine Compression (2002-2009 4.2L Chevrolet TrailBlazer).
• Electronic Throttle Body Tests (2002-2007 4.2L Chevrolet TrailBlazer).