DTC B2979 (2) (HVAC Control Unit)

DTC B2979 or DTC indicator 2  : An open in the A/C pressure sensor circuit

DTCs (AC)

1. Problem verification

   -1. Clear the DTC with the HDS.

   -2. Turn the vehicle to the OFF (LOCK) mode, then the ON mode.

   -3. Do the Self-Diagnostic Function with the HDS or the HVAC control unit .

   -4. Check for DTCs.

   DTC Description	DTC
   B2979 An open in the A/C pressure sensor circuit

   Is DTC B2979 or 2 indicated?

   YES 

   Go to step 2.

   NO 

   Intermittent failure. Check for loose wires or poor connections on the A/C pressure sensor circuit.

2. Open wire check (SENSOR 5V line)

   -1. Turn the vehicle to the OFF (LOCK) mode.

   -2. Disconnect the following connectors.

   HVAC control unit connector A (32P)

   A/C pressure sensor 3P connector

   -3. Check for continuity between test points 1 and 2.

   Test condition	Vehicle OFF (LOCK) mode
   	HVAC control unit connector A (32P): disconnected
   	A/C pressure sensor 3P connector: disconnected
   Test point 1	HVAC control unit connector A (32P) No. 5
   Test point 2	A/C pressure sensor 3P connector (female terminals) No. 3:

   Courtesy of HONDA, U.S.A., INC.

   Is there continuity?

   YES 

   The SENSOR 5V wire is not open. Go to step 3.

   NO 

   Repair an open in the wire between the HVAC control unit and the A/C pressure sensor.

3. Open wire check (SENSOR(COM) line)

   -1. Check for continuity between test points 1 and 2.

   Test condition	Vehicle OFF (LOCK) mode
   	HVAC control unit connector A (32P): disconnected
   	A/C pressure sensor 3P connector: disconnected
   Test point 1	HVAC control unit connector A (32P) No. 18
   Test point 2	A/C pressure sensor 3P connector (female terminals) No. 1:

   Courtesy of HONDA, U.S.A., INC.

   Is there continuity?

   YES 

   The SENSOR(COM) wire is not open. Go to step 4.

   NO 

   Repair an open in the wire between the HVAC control unit and the A/C pressure sensor.

4. Open wire check (PD SENSOR line)

   -1. Check for continuity between test points 1 and 2.

   Test condition	Vehicle OFF (LOCK) mode
   	HVAC control unit connector A (32P): disconnected
   	A/C pressure sensor 3P connector: disconnected
   Test point 1	HVAC control unit connector A (32P) No. 20
   Test point 2	A/C pressure sensor 3P connector (female terminals) No. 2:

   Courtesy of HONDA, U.S.A., INC.

   Is there continuity?

   YES 

   The PD SENSOR wire is not open. Go to step 5.

   NO 

   Repair an open in the wire between the HVAC control unit and the A/C pressure sensor.

5. HVAC control unit check 1

   -1. Reconnect the HVAC control unit connector A (32P).

   -2. Turn the vehicle to the ON mode.

   -3. Measure the voltage between test points 1 and 2.

   Test condition	Vehicle ON mode
   	A/C pressure sensor 3P connector: disconnected
   Test point 1	HVAC control unit connector A (32P) No. 5
   Test point 2	HVAC control unit connector A (32P) No. 18

   Is there about 5 V?

   YES 

   Go to step 6.

   NO 

   Replace the HVAC control unit .

6. HVAC control unit check 2

   -1. Measure the voltage between test points 1 and 2.

   Test condition	Vehicle ON mode
   	A/C pressure sensor 3P connector: disconnected
   Test point 1	HVAC control unit connector A (32P) No. 18

   Test point 2

   HVAC control unit connector A (32P) No. 20

   Is there about 5 V?

   YES 

   Replace the A/C pressure sensor .

   NO 

   Replace the HVAC control unit .