P0646-A/C CONTROL CIRCUIT LOW

For a complete wiring diagram Refer to Section 8W

When Monitored:
With the engine running and battery voltage greater than 10.4 volts.
Set Condition:
The PCM detects that the A/C Compressor control circuit voltage is below the minimum acceptable value.

Possible Causes

INTERMITTENT DTC

(C27) A/C COMPRESSOR CONTROL CIRCUIT SHORTED TO GROUND

(C27) A/C COMPRESSOR CONTROL CIRCUIT OPEN OR HIGH RESISTANCE

(Z916) GROUND CIRCUIT OPEN OR HIGH RESISTANCE

A/C COMPRESSOR

POWERTRAIN CONTROL MODULE (PCM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Diagnostic Test

1.DTC IS ACTIVE

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

Is the status Active for this DTC?

Yes

Go to 2

Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

2.(Z916) GROUND CIRCUIT OPEN OR HIGH RESISTANCE

NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.

Is the test light illuminated and bright?

Yes

Go to 3

Repair the (Z916) Ground circuit for an open circuit or high resistance.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

3.(C27) A/C COMPRESSOR CONTROL CIRCUIT SHORTED TO GROUND

Is the resistance below 100 ohms?

Yes

Repair the (C27) A/C Compressor Control circuit for a short to ground.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Go to 4

4.(C27) A/C COMPRESSOR CONTROL CIRCUIT OPEN OR HIGH RESISTANCE

Is the resistance below 5.0 ohms?

Yes

Go to 5

Repair the (C27) A/C Compressor Control circuit for an open circuit or high resistance.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

5.A/C COMPRESSOR

NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.

NOTE: The test light should not be illuminated.

Is the test light illuminated and bright with the actuation ON (100%) and not illuminated with the actuation OFF (0%)?

Yes

Replace the A/C Compressor in accordance with the Service Information.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Go to 6

6.POWERTRAIN CONTROL MODULE (PCM)

Were any problems found?

Yes

Repair as necessary.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).

Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information.
Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - STANDARD PROCEDURE).