HVAC
HVAC DTC Troubleshooting: 12
DTC 12: A Problem in the Blower Motor Circuit
1. Check the No. 12 (40 A) fuse in the under-hood fuse/relay box, and the No. 14 (10 A) fuse in the under-dash fuse/relay box.
Are the fuses OK?
YES - Go to step 2.
NO - Replace the fuse(s), and recheck. If either fuse blows again, check for a short in the No. 12 (40 A) or No. 14 (10 A) fuse circuits.
2. Connect terminal No. 2 of the blower motor 2P connector to body ground with a jumper wire.
3. Turn the ignition switch to ON (II).
Does the blower motor run?
YES - Go to step 4.
NO - Go to step 17.
4. Turn the ignition switch to LOCK (0).
5. Disconnect the jumper wire.
6. Disconnect the power transistor 4P connector.
7. Check for continuity between terminal No. 2 of the power transistor 4P connector and body ground.
Is there continuity?
YES - Go to step 8.
NO - Check for an open in the wire between the power transistor and body ground. If the wire is OK, check for poor body ground at G501. Dashboard Wire Harness A (Left Branch) and Tweeter Subharness Connector and Harness Locations
8. Connect terminals No. 2 and No. 4 of the power transistor 4P connector with a jumper wire.
9. Turn the ignition switch to ON (II).
Does the blower motor run at high speed?
YES - Go to step 10.
NO - Repair open in the BLU/BLK wire between the power transistor and the blower motor.
10. Turn the ignition switch to LOCK (0).
11. Disconnect the jumper wire.
12. Disconnect the heater control panel 30P connector.
13. Check for continuity between terminals No. 18 and No. 19 of the heater control panel 30P connector and body ground individually.
Is there continuity?
YES - Repair short to body ground in the wire(s) between the heater control panel and the power transistor.
NO - Go to step 14.
14. Check for continuity between the following terminals of the heater control panel 30P connector and the power transistor 4P connector.
Is there continuity?
YES - Go to step 15.
NO - Repair open in the wire(s) between the heater control panel and the power transistor.
15. Reconnect the heater control panel 30P connector.
16. Test the power transistor. Blower Power Transistor Test
Is the power transistor OK?
YES - Check for loose wires or poor connections at the heater control panel 30P connector and at the power transistor 4P connector. If the connections are good, substitute a known-good heater control panel, and recheck. If the symptom/indication goes away, replace the original heater control panel.
NO - Replace the power transistor.
17. Disconnect the jumper wire.
18. Disconnect the blower motor 2P connector.
19. Turn the ignition switch to ON (II).
20. Measure the voltage between terminal No. 1 of the blower motor 2P connector and body ground.
Is there battery voltage?
YES - Replace the blower motor. Blower Unit Component Replacement
NO - Go to step 21.
21. Turn the ignition switch to LOCK (0).
22. 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 23.
NO - Replace the blower motor relay.
23. Measure the voltage between terminal No. 3 of the blower motor relay 4P socket and body ground.
Is there battery voltage?
YES - Go to step 24.
NO - Replace the under-hood fuse/relay box. Under-Hood Fuse/Relay Box Removal and Installation
24. Turn the ignition switch to ON (II).
25. Measure the voltage between terminal No. 2 of the blower motor relay 4P socket and body ground.
Is there battery voltage?
YES - Go to step 26.
NO - Repair open in the wire between the No. 14 (10 A) fuse in the under-dash fuse/relay box and the blower motor relay.
26. Turn the ignition switch to LOCK (0).
27. Check for continuity between terminal No. 1 of the blower motor relay 4P socket and body ground.
Is there continuity?
YES - Repair open in the BLU/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 body ground at G301. Engine Compartment Wire Harness (Left Branch) Connector and Harness Locations
