GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Envoy - 4WD 🢒 Engine 🢒 Engine Controls - 4.2L 🢒 DTC P0340

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:

    • A 12-volt reference
    • A low reference
    • A CMP sensor signal

If the CMP Active Counter stops incrementing, DTC P0340 will set.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

The CMP Active Counter is not incrementing.

Action Taken When the DTC Sets
    • The malfunction indicator lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active.
    • The PCM records the operating conditions at the time when the diagnostic fails. This information stores in the Freeze Frame and Failure Records buffers.
    • A history DTC stores.

Conditions for Clearing the MIL/DTC
    • The MIL will turn OFF after three 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.
    • Use a scan tool to clear the DTCs.

Diagnostic Aids
    • Whenever the PCM sees less than 15 resyncs in 256 seconds, the counter resets to 0. When a poor connection is present, the cam sensor active counter stops incrementing and the cam sensor resync counter starts to increment.
        The following conditions may cause this DTC to set:
       - Damage to the camshaft reluctor wheel
       - Damage to the CMP sensor
       - 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. This step tests the output of the CMP sensor. If the duty cycle is not within the specified range the sensor is bad.

Step

Action

Values

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
  1. Start the engine.
  2. Observe the CMP Active Counter parameter with a scan tool.

Does the scan tool parameter increment?

--

Go to Step 3

Go to Step 4

3
  1. Observe the Freeze Frame/Failure Records for this DTC.
  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 4

Go to Diagnostic Aids

4
  1. Turn OFF the ignition.
  2. Disconnect the camshaft position (CMP) sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the 12-volt reference circuit to a good ground with a DMM. Refer to Probing Electrical Connectors in Wiring Systems.

Is the voltage more than the specified value?

10 V

Go to Step 5

Go to Step 7

5
  1. Turn OFF the ignition.
  2. Jumper the CMP circuits from the CMP sensor to the CMP sensor harness connector. Refer to Using Connector Test Adapters in Wiring Systems.
  3. Turn ON the ignition with the engine OFF.
  4. Measure the voltage drop from the low reference circuit of the CMP sensor to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.

Is the voltage more than the specified value?

0.2 V

Go to Step 8

Go to Step 6

6

  1. Leave the jumper wires installed.
  2. Remove the jumper wire from the CMP signal circuit on the powertrain control module (PCM) side.
  3. Start the engine.
  4. Measure the duty cycle from the CMP signal circuit on the sensor side and to a good ground with a DMM.

Is the duty cycle within the specified range?

40-50%

Go to Step 9

Go to Step 10

7

Test the 12-volt reference circuit for an open, high resistance or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 11

8

Test the low reference circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 11

9

Test the signal circuit for an open, short to ground or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 11

10

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 15

Go to Step 12

11

Test for an intermittent and for a poor connection at the PCM. 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 15

Go to Step 14

12
  1. Remove the CMP sensor.
  2. Visually inspect the CMP sensor for the following conditions:
    3. • Physical damage
    • Loose or improper installation

Did you find and correct the condition?

--

Go to Step 15

Go to Step 13

13

Replace the CMP sensor. Refer to Camshaft Position Sensor Replacement .

Did you complete the replacement?

--

Go to Step 15

--

14

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 15

--

15
  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 2

Go to Step 16

16

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