B1234
DTC Troubleshooting: B1234 or Indicator B and A/C ON
DTC B1234 or DTC indicator B and A/C ON:A Short in the Driver's Air Mix Control Motor Circuit
1. Clear the DTC with the HDS.
2. Turn the ignition switch to LOCK (0), and then to ON (II).
3. Do the self-diagnostic function with the HDS How to Troubleshoot the Climate Control System or climate control unit. How to Troubleshoot the Climate Control System
4. Check for DTCs.
Is DTC B1234 or B and A/C ON indicated?
YES - Go to step 5.
NO - Intermittent failure. Check for loose wires or poor connections on the driver's air mix control motor circuit.
5. Check for DTCs.
Are these DTCs also present; B121B or H and A/C ON, and/or B1220 or L and A/C ON, and/or B1237 or E and A/C ON?
YES - Go to step 13.
NO - Go to step 6.
6. Turn the ignition switch to LOCK (0).
7. Test the driver's air mix control motor. Air Mix Control Motor Test
Is the driver's air mix control motor OK?
YES - Go to step 8.
NO - Replace the driver's air mix control motor. Air Mix Control Motor Replacement
8. Disconnect the driver's air mix control motor 7P connector.
9. Disconnect climate control unit connectors A (28P) and B (12P).
10. Check for continuity between body ground and climate control unit connector A (28P) No. 14 terminal.
Is there continuity?
YES - Repair short to body ground in the wire between the climate control unit and the driver's air mix control motor.
NO - Go to step 11.
11. Check for continuity between climate control unit connector A (28P) No. 14 terminal and climate control unit connector B (12P) No. 12 terminal.
Is there continuity?
YES - Repair short in the wires.
NO - Go to step 12.
12. Turn the ignition switch to ON (II), and measure the voltage between climate control unit connector A (28P) No. 14 terminal and body ground.
Is there any voltage?
YES - Repair short to power in the wire between the climate control unit and the driver's air mix control motor. This short may also damage the climate control unit. Repair short to power before replacing the climate control unit.
NO - Substitute a known-good climate control unit, and recheck. If the symptom/indication goes away, replace the original climate control unit. Service and Repair
13. Turn the ignition switch to LOCK (0), and disconnect the climate control unit connector B (12P).
14. Disconnect these items:
- Driver's air mix control motor
- Passenger's air mix control motor
- Recirculation control motor
- Mode control motor
15. Check for continuity between climate control unit connector B (12P) No. 12 terminal and body ground.
Is there continuity?
YES - Repair short to body ground in the wire.
NO - Go to step 16.
16. Turn the ignition switch to ON (II), and check the same terminal for voltage between the terminal and body ground.
Is there any voltage?
YES - Repair short to power in the wire. This short may have also damaged the climate control unit. Repair short to power before replacing the climate control unit.
NO - Go to step 17.
17. Turn the ignition switch to LOCK (0).
18. Reconnect climate control unit connector B (12P).
19. Turn the ignition switch to ON (II), and measure the voltage between climate control unit connector B (12P) No. 12 terminal and body ground.
Is there about 5 V?
YES - Go to step 20.
NO - Check for a loose wire or poor connection at climate control unit connector B (12P). If the connection is good, substitute a known-good climate control unit and recheck. If the symptom/indication goes away, replace the original climate control unit. Service and Repair
20. While checking the same terminal for voltage to ground, reconnect these items individually and note the voltage reading each time:
- Driver's air mix control motor
- Passenger's air mix control motor
- Recirculation control motor
- Mode control motor
Does the voltage remain at about 5 V?
YES - Substitute a known-good climate control unit and recheck. If the symptom/indication goes away, replace the original climate control unit. Service and Repair
NO - Replace the component that caused the voltage drop.
