For 1990-2009 cars

### Circuit Description

The DTC P1656 Intake Camshaft Position (CMP) Actuator Solenoid Control Circuit diagnostic monitors the operation of the CMP actuator system. The CMP actuator system enables the powertrain control module (PCM) to change camshaft timing when the engine is running. The CMP actuator solenoid valve controls the oil flow that applies the pressure to advance or retard the camshaft. The PCM provides a pulse width modulated (PWM) signal for control of the CMP actuator solenoid.

### Conditions for Running the DTC

The ignition is ON.

### Conditions for Setting the DTC

The PCM detects an open or a short in the CMP actuator solenoid control circuit.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL).

• | The PCM stores the conditions that 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.

• | A 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.

### Test Description

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

1. The Diagnostic System Check-Engine Controls 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 the operation of the CMP actuator solenoid valve. This inspection is to be performed when the vehicle is idling at normal operating temperature. Turning ON the CMP actuator solenoid at idle will advance the camshaft enough to cause a significant drop in engine speed.

3. This step checks for electrical resistance in the wiring and connections of the CMP actuator solenoid circuit. Circuit resistance as small as 45 ohms can cause a DTC P1656 to set.

Step | Action | 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. Perform the scan tool Clear DTC Information function.
2. Start the engine.
3. Operate the engine for 1 minute.
4. Review the scan tool data and check for a DTC P1656.

Is a DTC P1656 set?

Go to Step 4

Go to Step 3

3 |

1. Start the engine.
2. Allow the engine to reach normal operating temperature.
3. Command the CMP actuator solenoid ON with the scan tool.

Does the engine idle very rough or stall when the CMP actuator solenoid is commanded ON with the scan tool?

Go to Intermittent Conditions

Go to Step 4

4 |

1. Start the engine.
2. Allow the engine to reach normal operating temperature.
3. Turn OFF the engine.
4. Disconnect the electrical connector to the CMP actuator solenoid valve.
5. Start and idle the engine.
6. Connect the CMP actuator solenoid to B+ and ground with a pair of fused jumper wires.

Does the engine idle very rough or stall when the CMP actuator solenoid is connected to B+?

Go to Step 5

Go to Step 7

5 |

1. Inspect the CMP ACT+ high circuit for an open or a short.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 10

Go to Step 6

6 |

1. Inspect the CMP ACT- low circuit for an open or a short.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 10

Go to Step 8

7 | Replace the CMP actuator solenoid valve. Refer to Camshaft Position Actuator Solenoid Valve Replacement . Is the action complete? | Go to Step 10 | --
8 |

1. Inspect the electrical circuits and connections of the CMP actuator solenoid for high electrical resistance.
2. Inspect for poor connections at the harness connectors of the PCM and the CMP actuator solenoid.
3. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 10

Go to Step 9

9 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | Go to Step 10 | --
10 |

1. Use the scan tool in order to clear the DTCs.
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 11

Go to Step 2

11 | 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