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

WARNING: This page is about a different car, the 2013 Acura MDX, 2012 Acura MDX, 2011 Acura MDX, and 2010 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.

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 climate control unit (see HOW TO USE THE SELF-DIAGNOSTIC FUNCTION WITHOUT THE HDS ).
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 in the A/C pressure sensor circuit.
Turn the ignition switch to LOCK (0).
Disconnect the A/C pressure sensor 3P connector.
Disconnect climate control unit connector A (40P).
Check for continuity between the following terminals of climate control unit connector A (40P) and the A/C pressure sensor 3P connector.
40P:

No. 6

No. 8

No. 26

3P:

No. 1

No. 3

No. 2

Fig 1: Checking For Continuity Between Following Terminals Of Climate Control Unit Connector A (40P) 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 climate control unit and the A/C pressure sensor.
Reconnect climate control unit connector A (40P).
Turn the ignition switch to ON (II).
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.

Fig 2: Measuring Voltage Between Climate Control Unit Connector A (40P) Terminals No. 6 And No. 8
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 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 (see CLIMATE CONTROL UNIT REMOVAL/INSTALLATION ).