Test No. 9: Back-Up Power Source Circuit

This circuit provides power for diagnostic code memory in cruise control ECU, even when ignition is off.

1. Check fuse protecting back-up power source circuit:
   • ECU-B fuse in engine compartment fuse/relay block.
2. If fuse is blown, repair short circuit. If fuse is okay, remove cruise control ECU, but leave electrical connector(s) attached. Measure voltage between ground and terminal No. 1 of cruise control ECU connector. See Figure.
3. If battery voltage is present, perform next procedure listed in DIAGNOSIS BY SYMPTOM  table under TROUBLE SHOOTING. If battery voltage is not present, repair circuit between battery and cruise control ECU.