For 1990-2009 cars
Engine Controls Component Views
Engine Speed Output, CKP, CMP and Knock Sensors
OBD II Symbol Description Notice

### Circuit Description

The Camshaft Position sensor is mounted through the top of the engine block at the rear of the valley cover. The CMP sensor works in conjunction with a 1X reluctor wheel on the camshaft. The reluctor wheel is inside the engine immediately in front of the rear cam bearing. The PCM provides a 12 volt power supply to the CMP sensor as well as a ground and a signal circuit.

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

Observe that as long as the PCM receives the Crankshaft Position sensor 24X signal, the engine will start. The PCM can determine top dead center for all cylinders by using the Crankshaft Position sensor 24X signal alone. The Camshaft Position sensor 1X signal is used by the PCM to determine if the cylinder at top dead center is on the firing stroke, or the exhaust stroke. The system attempts synchronization and looks for an increase in engine speed indicating the engine started. If the PCM does not detect an increase in engine speed, the PCM assumes it incorrectly synchronized 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 the Cam signal is stuck low when the signal should be high for 5.0 seconds.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

• | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records.

### Conditions for Clearing the MIL/DTC

• | The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

• | A last test failed, or current DTC, clears when the diagnostic runs and does not fail.

• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• | Use a scan tool in order to clear the MIL and the DTC.

### Diagnostic Aids

Important:

• | Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion into the PCM.

• | For any test that requires probing the PCM or component harness connectors, use the Connector Test Adapter Kit J 35616 . Using this kit prevents any damage to the harness connector terminals. Refer to Using Connector Test Adapters in Wiring Systems for procedures.

• | The following may cause this DTC to set:

- | Poor connections/terminal tension at the sensor. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

- | Camshaft reluctor wheel damage

- | The sensor coming in contact with the reluctor wheel

• | Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid determining how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This isolates when the DTC failed.

• | For an intermittent, refer to Symptoms .

### Test Description

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

1. This step verifies that the fault is present.

2. This step tests the Camshaft Position sensor B+ reference circuit from the PCM to the CMP jumper harness.

3. This step tests the Camshaft Position sensor ground circuit from the PCM to the CMP jumper harness.

4. This step tests the Camshaft Position sensor signal circuit. Applying a voltage causes the CAM signal input - High to Low and Low to High parameter to increase if the CMP signal circuit and the PCM are operating properly.

5. This step verifies the CMP sensor is capable of suppling a signal to the PCM. A duty cycle that is present, indicates the sensor is OK.

6. A duty cycle that is present, indicates the condition is intermittent. Inspect the jumper harness for poor connections.

7. This step tests the Camshaft Position sensor B+ reference circuit from the CMP jumper harness to the CMP sensor.

8. This step tests the Camshaft Position sensor ground circuit from the CMP jumper harness to the CMP sensor.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Install a scan tool.
2. Idle the engine.
3. Monitor the CAM signal input - High to Low and Low to High transition parameter in the Engine Data List 1 using the scan tool.

Does the scan tool parameter increment?

--

Go to Step 3

Go to Step 4

3 |

1. Turn ON the ignition leaving the engine OFF.
2. Review the Freeze Frame and/or Failure Records data for this DTC and observe the parameters.
3. Turn OFF the ignition for 15 seconds.
4. Idle the engine.
5. Operate the vehicle within the conditions required for this diagnostic to run, and as close to the conditions recorded in Freeze Frame/Failure Records as possible. Special operating conditions that you need to meet before the PCM will run this diagnostic, where applicable, are listed in Conditions for Running the DTC.
6. Select the Diagnostic Trouble Code (DTC) option, the Specific DTC option, then enter the DTC number using the scan tool.

Does the scan tool indicate that this diagnostic failed this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4 |

1. Turn OFF the ignition.
2. Disconnect the Camshaft Position sensor (CMP) jumper harness connector located near the EGR valve.
3. Turn ON the ignition leaving the engine OFF.
4. Measure the voltage at the Camshaft Position sensor ignition feed circuit (PCM side of jumper harness) using the DMM J 39200 .

Does the DMM display near the specified value?

B+

Go to Step 5

Go to Step 14

5 | Measure the voltage from the Camshaft Position sensor ignition feed circuit to the Camshaft Position sensor ground circuit (PCM side of jumper harness) using the DMM J 39200 . Does the DMM display near the specified voltage? | B+ | Go to Step 6 | Go to Step 16
6 |

1. Start the engine.
2. Monitor the CAM signal input - High to Low and Low to High transition in the Engine Data List 1 using the scan tool.
3. Momentarily and repeatedly probe the signal circuit (PCM side of jumper harness) with a fused jumper connected to B+. Refer to Using Fused Jumper Wires in Wiring Systems.

Does the CAM signal input - High to Low and Low to High transition counters increment when the jumper contacts the signal circuit?

--

Go to Step 7

Go to Step 17

7 |

1. At the CMP Jumper harness, jumper the ignition feed circuit between the PCM side of the harness to the camshaft position sensor side of the harness using a fused jumper wire. Refer to Using Fused Jumper Wires in Wiring Systems.
2. At the CMP Jumper harness, jumper the ground circuit between the PCM side of the harness to the camshaft position sensor side of the harness using a fused jumper wire. Refer to Using Fused Jumper Wires in Wiring Systems.
3. Idle the engine.
4. Connect the DMM J 39200 to the signal circuit (CMP side of harness) and ground.
5. Set the DMM to DC voltage and to the duty cycle (percentage) position.

Does the DMM display a percentage within the specified range?

45-55%

Go to Step 8

Go to Step 9

8 |

1. Inspect for a poor connection at the PCM to CMP sensor jumper harness. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
2. If you find a poor connection repair as necessary. Refer to Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Diagnostic Aids

9 |

1. Turn OFF the ignition.
2. Remove the intake manifold in order to gain access to the Camshaft Position sensor. Refer to Intake Manifold Replacement in Engine Mechanical.
3. Disconnect the Camshaft Position sensor electrical connector.
4. Reconnect the CMP jumper harness connector.
5. Turn ON the ignition leaving the engine OFF.
6. Measure the voltage from the Camshaft Position sensor B+ reference circuit to the battery ground using the DMM J 39200 .

Does the DMM display near the specified voltage?

B+

Go to Step 10

Go to Step 19

10 | Measure the voltage from the Camshaft Position sensor ignition feed circuit to the Camshaft Position sensor ground circuit using the DMM J 39200 . Does the DMM display near the specified voltage? | B+ | Go to Step 11 | Go to Step 21
11 |

1. Turn OFF the ignition.
2. Disconnect the CMP jumper harness connector.
3. Test the continuity of the CMP signal circuit (jumper harness) using the DMM J 39200 .

Is there continuity and is the resistance within the specified range?

0-2ohms

Go to Step 12

Go to Step 23

12 |

1. Turn ON the ignition Leaving the engine OFF.
2. Probe the CMP signal circuit with the DMM J 39200 connected to ground.

Is the voltage less than the specified value?

1.0V

Go to Step 13

Go to Step 25

13 | Probe the CMP signal circuit with the Test Lamp J 35616-200 connected to B+. Does the test Lamp illuminate? | -- | Go to Step 26 | Go to Step 31
14 |

1. Disconnect the PCM connector C2 located on the opposite side of the manufacturer's logo. Refer to Powertrain Control Module Replacement/Programming .
2. Test the continuity of the CMP ignition feed circuit using the DMM J 39200 .

Is there continuity and is the resistance within the specified range?

0-2ohms

Go to Step 15

Go to Step 28

15 |

1. Test the CMP ignition feed circuit for the following:

• | a short to ground.

• | a short to voltage.

2. If you find a condition, repair as necessary.

Did you find the condition?

--

Go to Step 27

Go to Step 33

16 |

1. Disconnect the PCM connector C1 located on the same side as the manufacturer's logo. Refer to Powertrain Control Module Replacement/Programming .
2. Test the continuity of the CMP ground circuit using the DMM J 39200 .

Is there continuity and is the resistance within the specified range?

0-5ohms

Go to Step 33

Go to Step 29

17 |

1. Disconnect the PCM connector C1 located on the same side as the manufacturer's logo. Refer to Powertrain Control Module Replacement/Programming .
2. Test the continuity of the CMP signal circuit using the DMM J 39200 .

Is there continuity and is the resistance within the specified range?

0-5ohms

Go to Step 18

Go to Step 30

18 |

• | Test the CMP signal circuit for the following:

• | A grounded circuit: refer to Testing for Short to Ground in Wiring Systems.

• | A circuit shorted to a voltage: refer to Measuring Voltage in Wiring Systems.

• | If you find a condition, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 33

19 |

1. Inspect the connection at the CMP and at the jumper harness connector for proper connections. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
2. If you find a poor connection repair as necessary. Refer to Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 20

20 | Repair the CMP ignition feed circuit for an open or a short to ground. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 35 | --
21 |

1. Inspect the connection at the CMP and at the jumper harness connector for proper connections. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
2. If you find a poor connection repair as necessary. Refer to Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 22

22 | Repair the CMP ground circuit for an open. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 35 | --
23 |

1. Inspect the connection at the CMP and at the jumper harness connector for proper connections. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
2. If you find a poor connection repair as necessary. Refer to Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 24

24 | Repair the CMP signal circuit for an open. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 35 | --
25 | Repair the CMP signal circuit for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 35 | --
26 | Repair the CMP signal circuit for a short to ground. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 35 | --
27 |

• | Repair the CMP ignition feed circuit for:

• | a short to ground.

• | a short to voltage.

• | Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Step 35

--

28 |

1. Test the CMP ignition feed circuit for an open circuit. Refer to Testing for Continuity in Wiring Systems.
2. If you find the circuit open, repair the CMP ignition feed circuit. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 33

29 | Repair the CMP ground circuit for an open. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 35 | --
30 | Repair the CMP signal circuit for an open. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 35 | --
31 |

1. Inspect the connection at the CMP harness connector for proper connections. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
2. If you find a poor connection repair as necessary. Refer to Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 32

32 | Replace the Camshaft Position sensor. Refer to Camshaft Position Sensor Replacement . Is the action complete? | -- | Go to Step 35 | --
33 |

1. Inspect for poor connections at the PCM. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
2. If you find a poor connection repair the condition as necessary. Refer to Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 35

Go to Step 34

34 | Important:: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | Go to Step 35 | --
35 |

1. Select the Diagnostic Trouble Code (DTC) option and the Clear DTC Information option using the scan tool.
2. Idle the engine at the normal operating temperature.
3. Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text, if applicable.

Does the scan tool indicate that this test ran and passed?

--

Go to Step 36

Go to Step 2

36 | Select the Capture Info option and the Review Info option using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to applicable DTC Table | System OK