P1546

Diagnostic Chart:

Refer to Engine Controls Schematics A/C Compressor Control

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. If an improper voltage level has been detected on the output circuit which controls the A/C compressor control relay, DTC P1546 will set

CONDITIONS FOR RUNNING THE DTC
The ignition is ON.

CONDITIONS FOR SETTING THE DTC
^ An improper voltage level has been detected on the output circuit which controls the A/C compressor control relay.
^ The above conditions are present for at least 30 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
^ The PCM will store conditions which were present when the DTC set as Failure Records data only. This information will not be stored as Freeze Frame data.

CONDITIONS FOR CLEARING THE MIL/DTC
^ A History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared by using a scan tool.

DIAGNOSTIC AIDS
Check for the following conditions:
^ Poor connection at the PCM - Inspect harness connectors for the following conditions:
- Backed out terminals
- Improper mating
- Broken locks
- Improperly formed or damaged terminals
- Poor terminal to wire connection
^ Damaged harness - Inspect the wiring harness for damage. If the harness appears to be OK, disconnect the PCM, turn ON the ignition 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.

If the DTC cannot be duplicated and is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set. Also refer to Testing for Intermittent and Poor Connections in Diagrams.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
1. The Powertrain On-Board Diagnostic (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.
12. The PCM utilizes Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.