GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The camshaft position (CMP) sensor produces a 6X plus a sync signal for each revolution of the exhaust camshaft. These signals are for control of sequential fuel injection and for exhaust camshaft phaser control. The CMP is connected directly to the powertrain control module (PCM) and consists of the following circuits:

    • 12-volt reference
    • Low reference
    • CMP sensor signal

If the PCM receives a minimum number of CMP resyncs within a calculated amount of time, diagnostic trouble code (DTC) P0341 will set.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

The PCM sees more than 15 CMP sensor resyncs in 256 seconds (4 minutes 16 seconds).

Action Taken When the DTC Sets

    • The malfunction indicator lamp (MIL) will illuminate after 2 consecutive ignition cycles in which the diagnostic runs with the malfunction present.
    • The PCM will record the operating conditions at the time that the diagnostic fails. The Freeze Frame and Failure Records buffers will store this information.
    • A history DTC stores.

Conditions for Clearing the MIL/DTC

    • The MIL will turn OFF after 3 consecutive ignition cycles in which the diagnostic runs without a fault.
    • A history DTC will clear after 40 consecutive warm up cycles without a fault.
    • A scan tool can clear the DTCs.

Diagnostic Aids

    • If the PCM sees less than 15 resyncs in 256 seconds, the counter is reset to 0. When a faulty electrical connection is present, the CMP Reference Activity counter will stop incrementing and the CMP Resync Counter will increment.
        The following conditions may cause this DTC to set :
       - Incorrect harness routing near secondary ignition components
       - Ignition coil arcing to wiring harnesses or IC module
       - Camshaft reluctor wheel damage
       - The sensor coming in contact with the reluctor wheel
       - Foreign material passing between the sensor and the reluctor wheel
    • If the condition is intermittent, refer to Intermittent Conditions .

Test Description

The number below refers to the step number on the diagnostic table.

  1. The counter should stop incrementing with the sensor electrical connector disconnected and set a DTC P0340. If the counter stills increments, this indicates that the PCM is malfunctioning.

Step

Action

Value(s)

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Turn ON the ignition, with the engine OFF.

Are any other DTCs set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3

  1. Start the engine.
  2. Observe the CMP Resync Counter on the scan tool.

Is the CMP Resync Counter incrementing?

--

Go to Step 4

Go to Diagnostic Aids

4

  1. Turn OFF the ignition.
  2. Disconnect the CMP sensor.
  3. Start the engine.
  4. Observe the CMP Resync on the scan tool.

Did the CMP Resync Counter stop incrementing?

--

Go to Step 5

Go to Step 6

5

  1. Turn OFF the engine.
  2. With the CMP connector still disconnected, connect a DMM set to the DC HZ scale from the CMP signal circuit (PCM side) to ground.
  3. Start the engine.

Does the DMM display a Hertz reading above the specified value?

0 Hz

Go to Step 6

Go to Step 7

6

Visually and physically inspect all circuits going to the CMP sensor for the following:

    • Being routed too close to secondary ignition wires or components.
    • Being routed too close to after-market add-on electrical equipment.
    • Being routed too close to solenoids, relays, and motors.

If you find incorrect routing, correct the harness routing.

Did you find and correct the condition?

--

Go to Step 11

Go to Step 9

7

Test for an intermittent and for a poor connection at the CMP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 11

Go to Step 8

8

Replace the camshaft position (CMP) sensor. Refer to Camshaft Position Sensor Replacement .

Did you complete the replacement?

--

Go to Step 11

--

9

  1. Disconnect the PCM.
  2. Check the CMP terminals for a faulty electrical connection.
  3. Repair the terminals as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 11

Go to Step 10

10

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 11

--

11

  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 12

Go to Step 2

12

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK