Circuit Description
Ignition voltage is supplied directly to the A/C compressor clutch relay. The powertrain control module (PCM) controls the relay by grounding the A/C compressor clutch relay control circuit via an internal solid state device called a driver. The driver supplies the ground for the component being controlled. Each driver has a fault line which is monitored by the PCM. When the PCM is commanding a component on, the voltage of the control circuit should be near 0 volts. When the PCM is commanding the control circuit to a component off, the voltage potential of the circuit should be near battery voltage. If the fault detection circuit senses a voltage other than what is expected, this DTC will set.
The PCM will monitor the A/C compressor clutch relay control circuit for the following:
| • | A short to ground |
| • | A short to voltage |
| • | An open circuit |
| • | An open relay coil |
| • | An internally shorted or excessively low resistance relay coil. |
When the PCM detects any of the above malfunctions, this DTC is set and the affected driver is disabled.
Conditions for Running the DTC
The ignition voltage is between 9.0 and 18.0 Volts.
Conditions for Setting the DTC
| • | A short to ground, an open circuit or a short to battery voltage is detected on the A/C compressor clutch relay control circuit. |
| • | The condition is 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 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
Important: Be sure to inspect PCM engine grounds for being secure and clean.
If DTC P1546 cannot be duplicated, reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determined how often the condition that caused the DTC to set occurs. This may assist in diagnosing the condition.
If the problem is intermittent, refer to Testing for Intermittent Conditions and Poor Connections .
Test Description
The numbers below refer to the step numbers on the diagnostic table:
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Listen for an audible click when the A/C compressor clutch relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
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The PCM utilizes Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: HVAC Schematics | |||
1 | Did you perform the HVAC Diagnostic System Check? | Go to Step 2 | |
Does the A/C compressor clutch relay turn ON and OFF with each command? | Go to Diagnostic Aids | Go to Step 3 | |
3 |
Does the test lamp illuminate? | Go to Step 4 | Go to Step 8 |
4 |
Does the test lamp turn ON and OFF with each command? | Go to Step 9 | 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 A/C compressor clutch relay control circuit of the A/C compressor clutch relay for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 10 |
7 | Test the A/C compressor clutch relay control circuit of the A/C compressor clutch relay for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 10 |
8 | Repair the ignition 3 voltage circuit of the A/C compressor clutch relay. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 13 | -- |
9 | Inspect for poor connections at the A/C compressor clutch relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 11 |
10 | Inspect for poor connections at the harness connector of the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 12 |
11 | Replace the A/C compressor clutch relay. Did you complete the replacement? | Go to Step 13 | -- |
|
Important: Perform the programming procedure for the PCM. Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 3.5L. Did you complete the replacement? | Go to Step 13 | -- | |
13 |
Does the DTC reset? | Go to Step 2 | System OK |
