Manufacturer Code Charts: 12
HVAC DTC Troubleshooting: 12
DTC indicator 12:
A Problem in the Blower Motor Circuit
1. Turn the ignition switch to LOCK (0), and then to ON (II).
2. Do the Self-Diagnostic Function with the HVAC control unit.
3. Check for DTCs.
Is DTC 12 indicated?
YES -
Go to step 4.
NO -
Intermittent failure. Check for loose wires or poor connections on the blower motor circuit.�
4. Turn the ignition switch to LOCK (0).
5. Check the No. 8 (40 A) fuse in the under-hood fuse/relay box, and the No. 16 (7.5 A) fuse in the driver's under-dash fuse/relay box.
Are the fuses OK?
YES -
Go to step 6.
NO -
Replace the fuse(s), and recheck. If the fuse(s) blows again, check for a short in the No. 8 (40 A) fuse and/or the No. 16 (7.5 A) fuse circuits.�
6. Disconnect the blower motor 2P connector.
7. Turn the ignition switch to ON (II).
8. Measure the voltage between blower motor 2P connector terminal No. 1 and body ground.
Is there battery voltage?
YES -
Go to step 9.
NO -
Go to step 28.
9. Turn the ignition switch to LOCK (0).
10. Reconnect the blower motor 2P connector.
11. Connect blower motor 2P connector terminal No. 2 to body ground with a jumper wire.
12. Turn the ignition switch to ON (II).
Does the blower motor run?
YES -
Go to step 13.
NO -
Replace the blower motor Blower Unit Component Replacement.�
13. Turn the ignition switch to LOCK (0).
14. Disconnect the jumper wire.
15. Disconnect the power transistor 4P connector.
16. Check for continuity between power transistor 4P connector terminal No. 2 and body ground.
Is there continuity?
YES -
Go to step 17.
NO -
Check for an open in the wire between the power transistor and body ground. If the wire is OK, check for poor ground at G302.�
17. Connect power transistor 4P connector terminals No. 2 and No. 4 with a jumper wire.
18. Turn the ignition switch to ON (II).
Does the blower motor run at high speed?
YES -
Go to step 19.
NO -
Repair an open in the GRN wire between the power transistor and the blower motor.�
19. Turn the ignition switch to LOCK (0).
20. Disconnect the jumper wire.
21. Disconnect the HVAC control unit 24P connector.
22. Check for continuity between body ground and HVAC control unit 24P connector terminals No. 18 and No. 19 individually.
Is there continuity?
YES -
Repair a short to body ground in the wire(s) between the HVAC control unit and the power transistor.�
NO -
Go to step 23.
23. Check for continuity between the following terminals of the HVAC control unit 24P connector and the power transistor 4P connector.
Is there continuity?
YES -
Go to step 24.
NO -
Repair an open in the wire(s) between the HVAC control unit and the power transistor.�
24. Turn the ignition switch to ON (II).
25. Measure the voltage between body ground and HVAC control unit 24P connector terminals No. 18 and No. 19 individually.
Is there any voltage?
YES -
Repair a short to power in the wires.�
NO -
Go to step 26.
26. Reconnect the HVAC control unit 24P connector.
27. Test the power transistor Blower Power Transistor Test.
Is the power transistor OK?
YES -
Check for loose wires or poor connections at the HVAC control unit 24P connector, and at the power transistor 4P connector. If the connections are good, substitute a known-good HVAC control unit, and recheck. If the symptom/indication goes away, replace the original HVAC control unit HVAC Control Unit Removal/Installation.�
NO -
Replace the power transistor.�
NOTE: If the power transistor is faulty, check the blower motor for damage. If necessary, replace the blower motor.
28. Turn the ignition switch to LOCK (0).
29. Remove the blower motor relay from the under-hood fuse/relay box, and test it Testing and Inspection.
Is the relay OK?
YES -
Go to step 30.
NO -
Replace the blower motor relay.�
30. Measure the voltage between blower motor relay 4P socket terminal No. 1 and body ground.
Is there battery voltage?
YES -
Go to step 31.
NO -
Replace the under-hood fuse/relay box Under-Hood Fuse/Relay Box Removal And Installation.�
31. Turn the ignition switch to ON (II).
32. Measure the voltage between blower motor relay 4P socket terminal No. 4 and body ground.
Is there battery voltage?
YES -
Go to step 33.
NO -
Repair an open in the wire between the No. 16 (7.5 A) fuse in the driver's under-dash fuse/relay box and the blower motor relay.�
33. Turn the ignition switch to LOCK (0).
34. Check for continuity between blower motor relay 4P socket terminal No. 3 and body ground.
Is there continuity?
YES -
Repair an open in the WHT wire between the blower motor relay and the blower motor.�
NO -
Check for an open in the wire between the blower motor relay and body ground. If the wire is OK, check for poor ground at G301.�