Possible causes, elimination, notes

Diagnosis conditions 

No control module fault stored.

No fault with supply voltage (5 volts).

Signal implausible 

1. Check temperature mixing valve for smooth operation.
2. Unplug connectors A, B, C and D from the heating/air-conditioning control.
3. Unplug connector from the temperature mixing valve drive motor.
4. Connect ohmmeter to connector C 8 and drive motor connector pin 1.

   Display: < 5 ohm

   Connect ohmmeter to connector B 8 and drive motor connector pin 2.

   Display: < 5 ohm

   Connect ohmmeter to connector A 12 and drive motor connector pin 3.

   Display: < 5 ohm;

   Connect ohmmeter to connector D 10 and drive motor connector pin 4.

   Display: < 5 ohm

   Connect ohmmeter to connector D 2 and drive motor connector pin 5.

   Display: < 5 ohm

5. Check wire from connector C 8 to drive motor pin 1 for short to B+ and short to ground.
6. Check wire from connector B 8 to drive motor pin 2 for short to B+ and short to ground.
7. Check wire from connector A 12 to drive motor pin 3 for short to B+.
8. Check wire from connector D 10 to drive motor pin 4 for short to B+ and short to ground.
9. Check wire from connector D 2 to drive motor pin 5 for short to B+ and short to ground.