P1545

CIRCUIT DESCRIPTION

HVAC Compressor Control Schematics:

The PCM uses Output Driver Modules (ODMs) to control many functions of the engine, and the transaxle. The ODMs supply the ground path for the PCM controlled device when the PCM commands the device ON. Each ODM is able to control several outputs. Unlike the Quad Driver Modules (QDMs) used in earlier model years, the ODMs are able to diagnose each output circuit. The PCM monitors the ODMs for circuit conditions that are incorrect for the commanded state of the ODM. If the PCM detects an improper circuit condition in the ODM that controls the A/C relay, DTC P1545 will set.

CONDITIONS FOR RUNNING THE DTC
^ The engine is running.
^ The system voltage is between 8-16 volts.

CONDITIONS FOR SETTING THE DTC
^ The PCM detects an improper voltage level on the output circuit that controls the A/C relay.
^ The condition exists for at least 10 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM will not illuminate the Malfunction Indicator Lamp (MIL).
^ The PCM will store the conditions present when the DTC set as Fail Records data only.

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

DIAGNOSTIC AIDS

NOTE: Refer to Connector Test Adapter Kit J 35616-A Notice in Service Precautions.

To determine whether an improper voltage level exists on the output circuit, the PCM compares the voltage level to the commanded state. For example, a failure condition exists if the PCM detects a low voltage level when the device is commanded OFF, or a high voltage level when the device is commanded ON.

Check for the following conditions:
^ Faulty connections at the PCM or the A/C relay.
^ Refer to Wiring Repairs in Diagrams.
^ A damaged harness.
Inspect the wiring harness for damage. If the harness appears to be OK, disconnect the PCM and turn the ignition ON. Connect a voltmeter between the A/C compressor clutch relay control circuit and chassis ground. Turn the ignition ON and observe the voltmeter while moving connectors and wiring harnesses related to the A/C relay. A change in voltage will indicate the location of the malfunction. If the condition is found, repair as necessary. Refer to Wiring Repairs in Diagrams.

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may assist in diagnosing the condition. The information may help determine how often the condition that set the DTC occurs.

RELAY TERMINAL IDENTIFICATION
Use the Underhood Fuse Block Assembly and/or the Rear Fuse Block Assembly details located in Engine Controls Component Views, to locate the correct cavities to probe during diagnosis. Four blade relays can be inserted two ways. The number designations (i.e., 30, 85, 86, 87, and 87a) displayed on the relays correspond directly to the cavity and NOT the numbering on the relay.

TEST DESCRIPTION

Steps 1 - 4:

Steps 5 - 15:

The numbers below refer to the step numbers on the diagnostic table.
2. Checks for proper key ON voltage throughout the A/C relay control circuit.
3. Checks to ensure proper current draw in the A/C Relay control circuit. If the current is too high, the driver will shut down.
4. Check the PCMs ability to control the relay.
7. Check for a short to chassis ground or the A/C relay control circuit which resulted in the blown fuse.
8. Checks for an open ignition feed circuit to the A/C relay.
9. Checks for a short to ground in the A/C relay control circuit.
11. Checks for a short to battery positive voltage in the A/C relay control circuit.
15. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.