Circuit Description
When the PCM detects that A/C has been requested, the PCM 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. For the C60 schematic refer to
A/C Compressor Clutch Controls - C60
or for the C68 schematic refer to
A/C Compressor Clutch Controls - C68
.
Conditions for Setting the DTC
The PCM has commanded the A/C ON and no voltage is detected on the A/C clutch status line for more than 5.0 seconds.
Action Taken When the DTC Sets
| • | The DTC will be stored in the PCM memory when the diagnostic runs and fails. |
| • | The Malfunction Indicator Lamp (MIL) will not illuminate. |
| • | The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail. |
| • | A last test failed (Current DTC) will clear when the ignition is cycled and the diagnostic runs and does not fail. |
| • | A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | PCM battery voltage is interrupted. |
| • | Using a Scan tool. |
Diagnostic Aids
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. For intermittents, refer to Symptoms .
Test Description
Number(s) below refer to step numbers on the diagnostic table.
-
A problem that may prevent the compressor from engaging may or may not cause a DTC P1546.
-
If the scan tool indicates that the A/C Status is ON, indicates that the status circuit is OK.
-
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.
-
Checks whether ignition voltage is available at the relay.
-
Determines if the A/C relay is at fault or the A/C status circuit is at fault. If the A/C clutch engages, indicates that the A/C Status circuit is OK.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
Does the A/C clutch operate properly? | -- | |||
Using a scan tool, monitor A/C Status display on the Engine 1 Data List. Does the scan tool indicate A/C Status as ON? | -- | |||
Does the scan tool indicate that this diagnostic failed this ignition? | -- | Go to Diagnostic Aids | ||
Does the test light illuminate? | -- | |||
Using a fused jumper wire, jump the ignition feed circuit to the A/C clutch status circuit at the A/C clutch relay electrical harness. Does the A/C clutch engage? | -- | |||
7 | Repair the faulty A/C clutch relay connection or faulty A/C clutch relay. Refer to A/C Relay replacement. Is the action complete? | -- | -- | |
8 | Repair the open A/C clutch status circuit from the splice to the PCM. Was the condition found and corrected? | -- | ||
9 | Repair the open ignition feed circuit to A/C relay. Is the action complete? | -- | -- | |
10 | Repair the open in A/C status circuit from A/C relay to splice. Is the action complete? | -- | -- | |
11 |
Important:: Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | -- | |
12 |
Does the scan tool indicate that this test ran and passed? | -- | ||
13 | Using the scan tool, select Capture Info, Review Info. Are any DTCs displayed that have not been diagnosed? | -- | Go to the applicable DTC table | System OK |
