DTC : B2979 (A-B1)

DTC B2979 or DTC screen A-B1  : An Open in the A/C Pressure Sensor Circuit

DTC (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 climate control unit .

   -4. Check for DTCs.

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

   Is DTC B2979 or screen A-B1 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 (S 5V line)

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

   -2. Disconnect the following connectors.

   Climate control unit connector A (28P)

   A/C pressure sensor 3P connector

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

   Test condition	Vehicle OFF (LOCK) mode
   	Climate control unit connector A (28P): disconnected
   	A/C pressure sensor 3P connector: disconnected
   Test circuit	S 5V
   Test point 1	Climate control unit connector A (28P) No. 12 (BRN)
   Test point 2	A/C pressure sensor 3P connector No. 3 (YEL)

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

   Is there continuity?

   YES 

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

   NO 

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

3. Open wire check (SENSER COM line)

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

   Test condition	Vehicle OFF (LOCK) mode
   	Climate control unit connector A (28P): disconnected
   	A/C pressure sensor 3P connector: disconnected
   Test circuit	SENSER COM
   Test point 1	Climate control unit connector A (28P) No. 27 (WHT)
   Test point 2	A/C pressure sensor 3P connector No. 1 (WHT)

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

   Is there continuity?

   YES 

   The SENSER COM wire is not open. Go to step 4.

   NO 

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

4. Open wire check (PD line)

   -1. Disconnect the following connector.

   Climate control unit connector B (36P)

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

   Test condition	Vehicle OFF (LOCK) mode
   	Climate control unit connector A (28P): disconnected
   	Climate control unit connector B (36P): disconnected
   	A/C pressure sensor 3P connector: disconnected
   Test circuit	PD
   Test point 1	Climate control unit connector B (36P) No. 25 (LT BLU)
   Test point 2	A/C pressure sensor 3P connector No. 2 (LT BLU)

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

   Is there continuity?

   YES 

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

   NO 

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

5. Climate control unit check 1

   -1. Reconnect climate control unit connector A (28P) .

   -2. Reconnect climate control unit connector B (36P) .

   -3. Turn the vehicle to the ON mode.

   -4. Measure the voltage between test points 1 and 2.

   Test condition	Vehicle ON mode
   	A/C pressure sensor 3P connector: disconnected
   Test circuit	S 5V, SENSOR COM
   Test point 1	Climate control unit connector A (28P) No. 12 (BRN)
   Test point 2	Climate control unit connector A (28P) No. 27 (WHT)

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

   Is there about 5 V?

   YES 

   Go to step 6.

   NO 

   Replace the climate control unit .

6. Climate 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 circuit	SENSOR COM, PD
   Test point 1	Climate control unit connector A (28P) No. 27 (WHT)
   Test point 2	Climate control unit connector B (36P) No. 25 (LT BLU)

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

   Is there about 5 V?

   YES 

   Replace the A/C pressure sensor .

   NO 

   Replace the climate control unit .