An Open In the A/C Pressure Sensor Circuit

DTC Troubleshooting: B2979 or Indicator B and Windshield Defrost

DTC B2979 or DTC indicator B and WINDSHIELD DEFROST: An Open in the A/C Pressure Sensor Circuit

1. Clear the DTC with the HDS.

2. Turn the ignition switch to LOCK (0), and then to ON (II).

3. Do the self-diagnostic function with the HDS Initial Inspection and Diagnostic Overview or climate control unit. Initial Inspection and Diagnostic Overview

4. Check for DTCs.

Is DTC B2979 or B and WINDSHIELD DEFROST indicated?
YES - Go to step 5.

NO - Intermittent failure, check for loose wires or poor connections on the A/C pressure sensor circuit.


5. Turn the ignition switch to LOCK (0).

6. Disconnect the A/C pressure sensor 3P connector.

7. Disconnect climate control unit connector A (40P).

8. Check for continuity between the following terminals of climate control unit connector A (40P) and the A/C pressure sensor 3P connector.





Is there continuity?
YES - Go to step 9.

NO - Repair open in the wire(s) between the climate control unit and the A/C pressure sensor.






9. Reconnect climate control unit connector A (40P).

10. Turn the ignition switch to ON (II).

11. Measure the voltage between climate control unit connector A (40P) terminals No. 6 and No. 8, and between climate control unit connector A (40P) terminals No. 8 and No. 26.

Is there about 5 V?
YES - Replace the A/C pressure sensor.

NO - Check for loose wires or poor connections at climate control unit connector A (40P) and at the A/C pressure sensor 3P connector. If the connections are good, substitute a known-good climate control unit, and recheck. If the symptom/indication goes away, replace the original climate control unit.