For 1990-2009 cars

### Diagnosis

The following table will diagnose the PCM controlled outputs from the output driver modules only. For diagnosis of the cooling fan circuit, refer to Electric Cooling Fan Diagnosis . For diagnosis of the cruise control module circuit, refer to Cruise Control Inoperative/Malfunctioning .

### Circuit Description

The powertrain control module (PCM) controls most components with electronic switches which complete a ground circuit when turned on. These switches are arranged in groups of 4 and 7, and are called either a surface mounted quad driver module, which can independently control up to 4 outputs (PCM) terminals or an output driver module (ODM), which can independently control up to 7 outputs. Not all outputs are always used.

Drivers are fault protected. If a relay or solenoid is shorted, having very low or zero resistance, or if the control side of the circuit is shorted to voltage, it would allow too much current flow into the PCM. The driver senses this and the output is turned off or its internal resistance increases to limit current flow and protect the PCM and driver. The result is high output terminal voltage when it should be low. If the circuit from B+ to the component or the component is open, or the control side of the circuit is shorted to ground, terminal voltage will be low. Either of these conditions is considered to be a driver fault.

### Diagnostic Aids

• | The scan tool has the ability to command certain components and functions on and off. If a component or function does not have this capability, operate the vehicle during its normal function criteria to test for an open or shorted circuit.

• | An open or short to ground will appear in the open positions on the scan tool only when it is not commanded by the PCM or scan tool, while a short to voltage will appear in the short positions on the scan tool only while the component is being commanded by the PCM or scan tool.

### Test Description

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

1. A FAULT in any of the positions indicates that an open or a short is present in the corresponding circuit for that position.

2. The FAULT going away after disconnecting the connector indicates that the component or the component side of the wiring harness is malfunctioning. If the scan tool indicates a malfunction after disconnecting the connector and verifying that no open or short is present in the circuit, then the PCM is malfunctioning.

3. An open or a short to ground will appear in the open positions on the scan tool only, when not commanded by the PCM or the scan tool, while a short to voltage will appear in the short positions on the scan tool only while the component is being commanded by the PCM or scan tool.

4. Proper operation of any component or function with no FAULT in any of the positions indicates that system operation is normal at this time.

5. The FAULT going away after disconnecting the connector indicates that the component or the component side of the wiring harness is malfunctioning. If the scan tool indicates a malfunction after disconnecting the connector and verifying that no open or short is present in the circuit, then the PCM is malfunctioning.

6. A component or function that failed to operate at this point indicates that the malfunction is not on the PCM side of the circuitry.

7. The replacement PCM must be programmed and the Crankshaft Position System Variation Learning procedure must be performed.

#### PCM Outputs

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. Turn on the ignition, leaving the engine off.
2. Use a scan tool in order to observe the Output Drivers.

Do any of the numbered positions have the FAULT below?

--

Go to Step 3

Go to Step 4

3 | Disconnect the component connected to the malfunctioning circuit. Is the FAULT still displayed in the corresponding Output Driver position? | -- | Go to Step 6 | Go to Step 9
4 | Use a scan tool in order to command the output being checked while watching the corresponding position for each circuit. Does any of the positions change to FAULT? | -- | Go to Step 7 | Go to Step 5
5 | Does the component or the function operate when commanded? | -- | Go to Step 11 | Go to Step 9
6 |

1. Turn off the ignition.
2. Test any component circuit with the FAULT for the following conditions:

• | An open

• | A short to voltage

• | A short to ground

3. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 11

Go to Step 10

7 |

1. Disconnect the component connector of the malfunctioning circuit.
2. Use a scan tool in order to command the output being tested while watching the corresponding position of that circuit.

Does the FAULT still display in the corresponding Output Driver position?

--

Go to Step 8

Go to Step 9

8 |

1. Turn off the ignition.
2. Test any component circuit with the FAULT for the following conditions:

• | A short to voltage

• | A short to ground

3. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 11

Go to Step 10

9 |

1. Refer to the appropriate portion of the service manual for any component that malfunctioned when commanded with the scan tool.
2. If a problem is found, repair as necessary.

Did you complete the repair?

--

Go to Step 11

--

10 | Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the repair? | -- | Go to Step 11 | --
11 | Operate the vehicle within the conditions under which the original symptom was observed. Does the system operate properly? | -- | System OK | Go to Step 2