Test Requirements
- HO2S heater fuse is OK. Refer to Wiring Diagrams for fuse number.
- Engine Control Module (ECM) -J623- fuses OK.
- Battery voltage at least 12.5 volts.
- All electrical consumers such as, lights and rear window defroster, switched off.
- Vehicles with automatic transmission, shift selector lever into position "P" or "N".
- A/C switched off.
- Ground connections between engine/transmission/chassis OK.
- Ignition switched OFF.