GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2001 🢒 Firebird 🢒 Engine 🢒 Engine Controls - 5.7L 🢒 DTC P0343

Circuit Description

The camshaft position (CMP) sensor works in conjunction with a 1X reluctor wheel on the camshaft. The PCM provides a 12-volt reference supply to the CMP sensor as well as a low reference and a signal circuit.

The CMP sensor determines whether a cylinder is on a firing stroke or on an exhaust stroke. When the camshaft rotates, the reluctor wheel interrupts a magnetic field that is produced by a magnet within the sensor. The sensor's internal circuitry detects this condition, and produces a signal which the PCM reads. The PCM uses this 1X signal in combination with the CKP sensor 24X signal in order to determine the crankshaft position and the stroke. This diagnostic monitors for a loss of a Camshaft Position sensor signal.

As long as the PCM receives the CKP sensor 24X signal, the engine will start. The PCM can determine top dead center for all cylinders by using the CKP sensor 24X signal alone. The PCM uses the CMP sensor 1X signal in order to determine if the cylinder at top dead center is on the firing stroke, or on the exhaust stroke. The system attempts synchronization and looks for an increase in the engine speed, indicating that the engine started. If the PCM does not detect an increase in the engine speed, the PCM assumes an incorrect synchronization to the exhaust stroke, and re-syncs to the opposite cam position. A slightly longer cranking time may be a symptom of this condition.

Conditions for Running the DTC

The engine speed is less than 4,000 RPM.

Conditions for Setting the DTC

The PCM detects that the Cam signal is stuck high, when the signal should be low for 1.5 seconds.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

The following conditions may cause this DTC to set:

    • Camshaft reluctor wheel damage
    • The sensor coming in contact with the reluctor wheel

For an intermittent condition, refer to Intermittent Conditions .

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step verifies that the fault is present.

    2.

  2. If the duty cycle is present at the PCM connector, the CMP sensor 12-volt reference and the low reference circuits are OK.

    3.

  3. This step tests the CMP sensor 12-volt reference circuit.

    4.

  4. This step tests the CMP sensor low reference circuit.

    5.

  5. This step tests for a short to B+ on the CMP sensor signal circuit.

    6.

  6. This step tests for a short to ground on the CMP sensor signal circuit.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Install a scan tool.
  2. Start the engine.
  3. Use a scan tool in order to monitor the CAM signal input, High to Low transition.

Does the scan tool parameter increment?

--

Go to Step 3

Go to Step 4

3
  1. Observe the Freeze Frame/Failure Records data 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, as specified in the supporting text. Attempt to duplicate the Freeze Frame/Failure Records data that you observed.

Does the DTC fail this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4

  1. Disconnect PCM connector C-1. Refer to Powertrain Control Module Replacement .
  2. Remove the CMP signal wire pin from the PCM harness connector.
  3. Reconnect the PCM connector with the signal pin removed.
  4. Start the engine.
  5. Measure the duty cycle from the CMP signal pin at the PCM connector with the DMM.

Does the DMM display a duty cycle within the specified range?

45-55%

Go to Step 17

Go to Step 5

5

  1. Turn OFF the ignition.
  2. Disconnect the PCM connector C-1 and reinstall the CMP signal pin to the harness connector.
  3. Reconnect the PCM connectors. Refer to Powertrain Control Module Replacement .
  4. Remove the intake manifold in order to gain access to the CMP sensor. Refer to Intake Manifold Replacement in Engine Mechanical-5.7L.
  5. Disconnect the CMP sensor electrical connector.
  6. Turn ON the ignition, with the engine OFF.
  7. Measure the voltage from the CMP sensor 12-volt reference circuit to the battery ground with the DMM.

Does the DMM display the specified voltage?

B+

Go to Step 6

Go to Step 8

6

Measure the voltage from the CMP sensor 12-volt reference circuit to the CMP sensor low reference circuit with the DMM.

Does the DMM display the specified voltage?

B+

Go to Step 9

Go to Step 7

7

Test for an open in the CMP sensor low reference circuit. Refer to Testing for Continuity in Wiring Systems.

Did you find an open low reference circuit?

--

Go to Step 13

Go to Step 17

8

Test for an open or a short to ground in the CMP sensor 12-volt reference circuit. Refer to Circuit Testing in Wiring Systems.

Did you find the circuit open or shorted to a ground?

--

Go to Step 12

Go to Step 17

9

  1. Turn ON the ignition, with the engine OFF.
  2. Measure the voltage at the CMP sensor signal circuit to ground with the DMM.

Is the voltage less than the specified value?

1 V

Go to Step 10

Go to Step 14

10

Probe the CMP signal circuit with the test lamp connected to battery voltage.

Does the test lamp illuminate?

--

Go to Step 15

Go to Step 11

11
  1. Turn OFF the ignition.
  2. Disconnect the PCM connector C1, located on the same side as the manufacturer's logo. Refer to Powertrain Control Module Replacement .
  3. Test the continuity of the CMP sensor signal circuit with the DMM. Refer to Testing for Continuity in Wiring Systems.

Is the resistance less than the specified value?

2 ohms

Go to Step 18

Go to Step 16

12

Repair the open or short to ground in the CMP sensor 12-volt reference circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 20

--

13

Repair the open in the CMP sensor low reference circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 20

--

14

Repair the short to voltage on the CMP sensor signal circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 20

--

15

Repair the short to ground in the CMP sensor signal circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 20

--

16

Repair the open in the CMP sensor signal circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 20

--

17
  1. Inspect for poor connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. If you find a poor connection, repair the connection as necessary. Refer to Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 20

Go to Step 19

18

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

Did you complete the replacement?

--

Go to Step 20

--

19

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 20

--

20
  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 as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 21

Go to Step 2

21

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK