DTC B2991: Climate Control Unit Lost Communication with Audio System

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 ).
Check for DTCs.
Is DTC B2991 indicated?

YES -Go to step 5.

NO -Intermittent failure, check for loose wires or poor connections in the rear climate control panel and climate control unit circuit.
Turn the ignition switch to LOCK (0).
Disconnect climate control unit connector B (14P).
Disconnect audio unit (without navigation) connector C (24P) or audio-navigation unit (with navigation) connector F (20P).
Check for continuity between climate control unit connector B (14P) terminal No. 8 and audio unit (without navigation) connector C (24P) terminal No. 24 or audio-navigation unit (with navigation) connector F (20P) terminal No. 10.
Without navigation

Fig 1: Checking For Continuity Between Climate Control Unit Connector B (14P) Terminal No. 8 And Audio Unit (Without Navigation) Connector C (24P) Terminal No. 24
Courtesy of AMERICAN HONDA MOTOR CO., INC.

With navigation

Fig 2: Checking For Continuity Between Climate Control Unit Connector B (14P) Terminal No. 8 And Audio-Navigation Unit (With Navigation) Connector F (20P) Terminal No. 10
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Go to step 9.

NO -Repair an open in the wire between the climate control unit and the audio unit (without navigation) or audio-navigation unit (with navigation).
Check for continuity between climate control unit connector B (14P) terminal No. 8 and body ground.

Fig 3: Checking For Continuity Between Climate Control Unit Connector B (14P) Terminal No. 8 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Repair a short to body ground in the wire between the climate control unit and the audio unit (without navigation) or audio-navigation unit (with navigation).

NO -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 ). If the symptom/indication remains, substitute a known-good audio unit (without navigation) or audio-navigation unit (with navigation). If the symptom/indication goes away, replace the original audio unit (without navigation) (see AUDIO UNIT REMOVAL/INSTALLATION ) or the original audio-navigation unit (with navigation) (see AUDIO-NAVIGATION UNIT REMOVAL/INSTALLATION ).