P1546
P1546 A/C Clutch Output Circuit Fault
Circuit Description
When the powertrain control module (PCM)/engine control module (ECM) detects that A/C has been requested, the PCM/ECM will activate the A/C clutch relay. When the relay has been activated, voltage should be present at both the A/C compressor clutch and the A/C clutch status circuit at the PCM/ECM.
Conditions for Setting the DTC
- Ignition ON and voltage is greater than 10 volts.
- Engine run time is more than 5 seconds.
- The PCM/ECM has commanded the A/C ON and no voltage is detected on the A/C clutch status line for more than 5 seconds.
Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will not illuminate.
- The PCM/ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records butters.
- A history DTC is stored.
Conditions for Clearing the MIL/DTC
- The MIL will turn off after three consecutive ignition cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm-up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.
Diagnostic Aids
Check for the following conditions:
- Poor connection at the PCM/ECM. 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 OK, observe the throttle position display on the scan tool while moving connectors and wiring harnesses related to the Throttle Position (TP) sensor. A change in the display will indicate the location of the fault.
Step 1 - 6:
Step 7 - 13:
Test Description
The number(s) below refer to step(s) on the diagnostic table.
1. The On-Board Diagnostic (OBD II) System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
2. A problem that may prevent the compressor from engaging may or may not cause DTC P1546 to set.
3. If the scan tool indicates that the A/C request is ON, then the status circuit is OK.
4. Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If the DTC cannot be duplicated, the information included in the Freeze Frame and/or Failure Records data can be useful in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also be used to determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate vehicle within the same freeze frame conditions (rpm, load, vehicle speed temperature, etc.) that were noted. This will isolate when the DTC failed.
5. Checks whether ignition voltage is available at the relay.
6. Determines if the A/C relay is at fault or the A/C request circuit is at fault. If the A/C clutch engages, this indicates that the A/C status circuit is OK.
10. The replacement PCM/ECM must be reprogrammed. Refer to the latest Techline procedure for PCM/ECM reprogramming.