4A

Control System DTCs

DTC Troubleshooting: B121B - (4A)

DTC B121B or DTC indicator 4A : A Short in the Mode Control Motor Circuit


1. Problem verification:

-1. Clear the DTCs with the HDS.

-2. Turn the ignition switch to LOCK (0), and then back to ON (II).

-3. Do the Self-Diagnostic Function with the HDS or the climate control unit How to Troubleshoot the Climate Control System.

-4. Check for DTCs.






Is DTC B121B or 4A indicated?
-YES- Go to step 2.
-NO- Intermittent failure. Check for loose wires or poor connections on the mode control motor circuit.

2. DTC check:

-1. Turn the ignition switch to LOCK (0).

-2. Disconnect the following connector.






-3. Turn the ignition switch to ON (II).

-4. Do the Self-Diagnostic Function with the HDS or the climate control unit How to Troubleshoot the Climate Control System.

-5. Check for DTCs with the HDS.






Is DTC B121B or 4A indicated?
-YES- Go to step 3.
-NO- Replace the mode control motor Mode Control Motor Removal And Installation.

3. Mode control motor S5V line check:

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










Is there 5 V?
-YES- Go to step 4.
-NO- Go to step 5.

4. Shorted wire check (MODE-P line):

-1. Turn the ignition switch to LOCK (0).

-2. Disconnect the following connector.






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










Is there continuity?
-YES- Repair a short in the wire between the climate control unit and the mode control motor.
-NO- The MODE-P wire is OK. Replace the climate control unit Climate Control Unit Removal And Installation (Climate Control).

5. Shorted wire check (SENSOR 5V line):

-1. Turn the ignition switch to LOCK (0).

-2. Disconnect the following connector.






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










Is there continuity?
-YES- Repair a short in the wire between the climate control unit and the mode control motor.
-NO- The SENSOR 5V wire is OK. Replace the climate control unit Climate Control Unit Removal And Installation (Climate Control).