For 1990-2009 cars
Engine Controls Components
Cell 20: CMP and CKP Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The camshaft position (CMP) sensor is a magnetic generator type sensor that produces an alternating current signal. The CMP sensor signal increases in frequency as the engine RPM increases. The camshaft position signal is used by the PCM to determine optimum ignition timing and fuel delivery as well as misfire diagnosis. The engine will start and run without the CMP sensor signal.

### Conditions for Setting the DTC

No CMP sensor signal to the PCM while cranking.

OR

No CMP sensor signal to PCM with engine speed at 600 RPM or more.

### Action Taken When the DTC Sets

• | The PCM illuminates the MIL.

• | The PCM stores the conditions which were present when the DTC set as Freeze Frame Data.

### Conditions for Clearing the MIL/DTC

• | The PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.

• | The DTC clears after 40 consecutive warm-up cycles have occurred without a fault.

• | A DTC can be cleared by using the scan tool Clear DTC Information function.

### Diagnostic Aids

Check for any of the following conditions:

• | The camshaft position (CMP) sensor output may be affected by temperature. Check the sensor's operation and internal resistance at various temperatures. The CMP sensor resistance when COLD should be between 835 ohms and 1,400 ohms at -10° to 50°C (14°-122°F). The CMP sensor resistance when HOT should be between 1,060 ohms and 1,645 ohms at 50°-100°C (122°-212°F).

• | CMP sensor performance can be checked with a DMM and a scan tool. The AC voltage output of the CMP sensor, as measured with a DMM across the sensor electrical terminals, is approximately the same as engine speed. Run the engine at several different engine speeds and compare the numerical value on the scan tool with the numerical voltage reading on the DMM. If the reading of the DMM and the scan tool are not nearly equal, check for a faulty sensor or signal rotor.

• | A DTC P0340 that sets while driving and checks OK may be caused by inadequate CMP sensor circuit shielding. Check that the CMP sensor circuit is properly shielded and that the drain wire is fastened securely to ground.

An intermittent malfunction may be caused by a fault in the CMP sensor electrical circuit. Inspect the wiring harness and components for any of the following conditions:

• | Backed out terminals.

• | Improper mating of terminals.

• | Broken electrical connectors locks.

• | Improperly formed or damaged terminals

• | Faulty terminal to wire connections.

• | Physical damage to the wiring harness.

• | A broken wire inside the insulation.

• | Corrosion of electrical connections, splices, or terminals.

Repair any electrical circuit faults that were found. Refer to Wiring Repairs in Wiring Systems.

The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.

### Test Description

The numbers below refer to the step numbers in the Diagnostic Table.

1. The OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step checks for an open in the ground circuit of the CMP sensor from PCM terminal C1-17 to splice S209. The engine will not stay running, and a DTC P0340 will set, if the CMP sensor -- and CKP sensor -- ground circuit is open.

3. This step checks whether DTC P0340 is the result of a hard failure or an intermittent condition.

4. This step is checking the internal resistance of the camshaft position sensor. A typical value at 23°C (74°F) is 1.1k ohms.

5. This step checks the CMP sensor output signal. The CMP sensor sends the PCM one electrical pulse (signal) for every revolution of the intake camshaft. Therefore the AC signal generated by the CMP sensor will be numerically analogous to the engine speed. With the engine speed at about 3,000 RPM, the CMP sensor voltage should be around 2.950-3.050 volts AC.

6. This step checks the CKP input circuit to the PCM. The AC signal generated by the CMP sensor will be numerically analogous to the engine speed. With the engine speed at about 3,000 RPM, the CMP sensor voltage should be around 2.950-3.050 volts AC. The CMP sensor signal wire must be removed from the PCM connector in order to accurately check the sensor output. If the CMP sensor signal (input) wire is backprobed while connected to the PCM, the AC voltage indicated on a DMM will be approximately 15% to 20% lower than actual engine speed.

7. This step checks for a faulty signal rotor on the camshaft. Visually inspect the tooth of the signal rotor through the CMP sensor aperture for damage, foreign material, and installation.

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 | Does the vehicle not start or almost start and then stall immediately? | -- | Go to Step 10 | Go to Step 3
3 | Does the vehicle start and run with the MIL illuminated and a DTC P0340 set? | -- | Go to Step 5 | Go to Step 4
4 |

1. Install a scan tool.
2. Turn ON the ignition, leaving the engine OFF.
3. Save the DTC and Freeze Frame information.
4. Clear the DTC and scan tool information.
5. Operate the vehicle within the Freeze Frame conditions as specified.

Did a DTC P0340 set?

--

Go to Step 5

Go to Diagnostic Aids

5 |

1. Turn OFF the ignition.
2. Disconnect the CMP sensor electrical connector.
3. Measure the resistance of the CMP sensor with a DMM.

Is the CMP sensor resistance within the specified value?

835-1,400 ohms at -10° to 50°C (14°-122°F) or 1,060-1,645 ohms at 50°-100°C (122°-212°F)

Go to Step 6

Go to Step 13

6 |

1. Install a scan tool.
2. Connect the DMM across the CMP sensor terminals.
3. Select AC voltage on the DMM.
4. Start the engine.
5. Observe the AC voltage on the DMM while checking engine speed (RPM) on the scan tool. Refer to Test Descriptions.

Was the AC voltage indicated approximately equal to the engine speed?

--

Go to Step 7

Go to Step 12

7 | Probe the ground circuit of the CMP sensor (harness side) with a test lamp connected to B+. Did the test lamp illuminate? | -- | Go to Step 8 | Go to Step 11
8 |

1. Disconnect the PCM electrical connector C1.
2. Remove the CMP input (signal) wire, terminal C1-5, from the PCM electrical connector C1.
3. Reconnect the electrical connector C1 to the PCM, leaving the CMP input (signal) wire free to be tested.
4. Connect the DMM to the CMP input (signal) wire and ground.
5. Start the engine.
6. Observe the AC voltage on the DMM while observing engine speed (RPM) on the scan tool.

Was the AC voltage indicated approximately equal to the engine speed?

--

Go to Step 14

Go to Step 9

9 | Repair the open or the short in the CMP input circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 15 | --
10 | Repair the open in the CMP and CKP sensors ground circuit between splice S209 and the PCM. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 15 | --
11 | Repair the open in the CMP sensor ground circuit between the sensor and splice S209. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 15 | --
12 |

1. Remove the CMP sensor. Refer to Camshaft Position Sensor Replacement .
2. Visually inspect the CMP sensor signal rotor for the following conditions:

• | Missing or damaged tooth

• | Foreign material

• | Correct installation

3. Repair as necessary.

Was a repair necessary?

--

Go to Step 15

Go to Step 13

13 | Replace the CMP sensor. Refer to Camshaft Position Sensor Replacement . Is the action complete? | -- | Go to Step 15 | --
14 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 15 | --
15 |

1. Perform the scan tool Clear DTC Information function and road test the vehicle within the Freeze Frame conditions that set the DTC.
2. Review the scan tool data and check for DTCs. The repair is complete if no DTCs are stored.

Are any DTCs displayed on scan tool?

--

Go to the applicable DTC table

System OK