DTC B1239 or DTC indicator A and MODE: An Open or Short in the Mode Control Motor Circuit (Front)

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 B1239 or A and MODE indicated?

YES -Go to step 5.

NO -Intermittent failure, check for loose wires or poor connections in the front mode control motor circuit.
Turn the ignition switch to LOCK (0).
Test the front mode control motor (see FRONT MODE CONTROL MOTOR TEST ).
Is the front mode control motor OK?

YES -Go to step 7.

NO -Replace the front mode control motor (see RECIRCULATION CONTROL MOTOR REPLACEMENT ).
Disconnect the front mode control motor 7P connector.
Disconnect climate control unit connector A (40P).
Check for continuity between the following terminals of climate control unit connector A (40P) and the front mode control motor 7P connector.
40P:

No. 8

No. 31

No. 32

No. 33

No. 34

7P:

No. 7

No. 6

No. 5

No. 4

No. 3

Fig 1: Checking For Continuity Between Following Terminals Of Climate Control Unit Connector A (40P) And Front Mode Control Motor 7P Connector
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Go to step 10.

NO -Repair an open in the wire(s) between the climate control unit and the front mode control motor.
Check for continuity between body ground and climate control unit connector A (40P) terminals No. 31, No. 32, No. 33, and No. 34 individually.

Fig 2: Checking For Continuity Between Body Ground And Climate Control Unit Connector A (40P) Terminals No. 31, No. 32, No. 33, And No. 34
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Repair a short to body ground in the wire(s) between the climate control unit and the front mode control motor.

NO -Go to step 11.

Check for continuity between climate control unit connector A (40P) terminals as follows.

From terminal	To terminals
31	32, 33, 34
32	33, 34
33	34

Fig 3: Checking For Continuity Between Climate Control Unit Connector A (40P) Terminals

Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity between any of the terminals?

YES -Repair a short in the wires.

NO -Go to step 12

Turn the ignition switch to ON (II), and measure the voltage between the same terminal and body ground.

Fig 4: Measuring Voltage Between Same Terminal And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there any voltage?

YES -Repair a short to power in the wire(s) between the climate control unit and the front mode control motor. This short may also damage the climate control unit. Repair a short to power before replacing the climate control unit.

NO -Check for loose wires or poor connections at climate control unit connector A (40P) and at the front mode control motor 7P 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 ).