For 1990-2009 cars

Refer to Engine Controls Schematics for a wiring diagram.

### Circuit Description

Output Driver Modules (ODMs) are used by the PCM to turn on many of the current-driven devices that are needed to control various engine and Transaxle functions. Each ODM is capable of controlling up to 7 separate outputs by applying ground to the device which the PCM is commanding ON. Unlike the Quad Driver Modules (QDMs) used in prior model years, ODMs have the capability of diagnosing each output circuit individually. DTC P1641 set indicates an improper voltage level has been detected on the output circuit which controls the A/C compressor control relay.

### Conditions for Running the DTC

The ignition is ON.

### Conditions for Setting the DTC

• | An improper voltage level has been detected on ODM A output 1 (the A/C compressor control relay control circuit).

• | The above conditions are present for at least 30 seconds.

### Action Taken When the DTC Sets

The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.

### Conditions for Clearing the MIL/DTC

• | The DTC becomes history when the conditions for setting the DTC are no longer present.

• | The history DTC clears after 40 malfunction free warm-up cycles.

• | The PCM receives a clear code command from the scan tool.

### Diagnostic Aids

Check for the following conditions:

• | Poor connection at the PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

• | Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, disconnect the PCM, turn the ignition ON and observe a digital multimeter connected between the A/C compressor control relay control circuit and ground at the PCM harness connector while moving connectors and wiring harnesses related to the A/C compressor control relay. A change in voltage will indicate the location of the malfunction.

Review the Freeze Frame/Fail Records vehicle mileage since the diagnostic test last failed. This may help determine how often the condition that caused the DTC to be set occurs.

### Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

1. The powertrain OBD System Check prompts you to complete some basic checks and store the freeze frame and failure records data on the scan tool.

2. Listen for an audible click when the relay operates. Command both the ON and OFF states. Repeat the commands as necessary.

3. Tests for voltage at the coil feed side of the relay.

4. Verifies that the PCM is providing ground to the relay.

5. Tests if ground is constantly being applied to the relay.

6. The PCM utilizes Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.

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, with the engine OFF.
2. With a scan tool, command the A/C relay ON and OFF.

Does the relay turn ON and OFF with each command?

--

Go to Diagnostic Aids

Go to Step 3

3 |

1. Turn OFF the ignition.
2. Disconnect the relay.
3. Turn ON the ignition, with the engine OFF.
4. Probe the coil feed circuit of the relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 4

Go to Step 10

4 |

1. Connect a test lamp between the control circuit of the relay and the coil feed circuit of the relay.
2. With a scan tool, command the A/C relay ON and OFF .

Does the test lamp turn ON and OFF with each command?

--

Go to Step 8

Go to Step 5

5 | Does the test lamp remain illuminated with each command? | -- | Go to Step 7 | Go to Step 6
6 | Test the control circuit of the relay for a short to voltage or an open. Refer to Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 9
7 | Test the control circuit of the relay for a short to ground. Refer to Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 9
8 | Inspect for poor connections at the relay. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11
9 | Inspect for poor connections at the PCM. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12
10 | Repair the feed circuit of the relay. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 13 | --
11 | Replace the relay. Refer to Electrical Center Identification Views . Did you complete the replacement? | -- | Go to Step 13 | --
12 | Important: Perform the set up procedure for the PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the replacement? | -- | Go to Step 13 | --
13 |

1. Use the scan tool in order to clear the DTCs .
2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK