DTC B2979 or DTC indicator 6: An Open in the A/C Pressure Sensor Circuit

Clear the DTCs with the HDS.
Turn the ignition switch to LOCK (0) and then back to ON (II).
Do the self-diagnostic function with the HDS (see HOW TO USE THE SELF-DIAGNOSTIC FUNCTION WITH THE HDS ) or the HVAC control unit (see HOW TO USE THE HVAC CONTROL UNIT SELF-DIAGNOSTIC FUNCTION WITHOUT THE HDS ).
Check for DTCs.
Is DTC B2979 or 6 indicated?

YES -Go to step 5.

NO -Intermittent failure, check for loose wires or poor connections in the A/C pressure sensor circuit.
Turn the ignition switch to LOCK (0).
Disconnect the A/C pressure sensor 3P connector.
Disconnect HVAC control unit connector A (24P).
Check for continuity between the following terminals of HVAC control unit connector A (24P) and the A/C pressure sensor 3P connector.
24P: 3P:

No. 4 No. 3

No. 14 No. 1

No. 20 No. 2

Fig 1: Checking Continuity Between Terminals Of HVAC Control Unit Connector A (24P) And A/C Pressure Sensor 3P Connector
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Go to step 9.

NO -Repair an open in the wire(s) between the HVAC control unit and the A/C pressure sensor.
Reconnect HVAC control unit connector A (24P).
Turn the ignition switch to ON (II).
Measure the voltage between HVAC control unit connector A (24P) terminals No. 4 and No. 14, and between HVAC control unit connector A (24P) terminals No. 4 and No. 20.

Fig 2: Measuring Voltage Between HVAC Control Unit Connector A (24P) Terminals No. 4 And 14 And Between Terminals No. 4 And 20
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there about 5 V?

YES -Replace the A/C pressure sensor.

NO -Check for loose wires or poor connections at HVAC control unit connector A (24P) and at the A/C pressure sensor 3P connector. If the connections are good, substitute a known-good HVAC control unit, and recheck. If the symptom/indication goes away, replace the original HVAC control unit (see HVAC CONTROL UNIT REMOVAL/INSTALLATION ).