Diagnostic Procedure (Signal Too High Or Missing)

CAUTION: DO NOT apply rust solvent spray or grease to heated oxygen sensor connector.

Check wiring and electrical connectors for signs of corrosion, damage and poor connection. See CHECKING WIRING & CONNECTIONS . Repair as necessary and go to next step.
Connect breakout box. See CONNECTING & DISCONNECTING BREAKOUT BOX .
NOTE: An electrician's screwdriver with a 3-Watt (minimum) bulb will help diagnosis for short circuit to supply voltage.
Check signal cable (+) between rear heated oxygen sensor terminal No. 4 and PCM terminal A61 (breakout box terminal B1) for a short to supply voltage and a short to ground. See Figure. Repair as necessary and go to next step.
Check signal cable (-) between rear heated oxygen sensor terminal No. 3 and PCM terminal A62 (breakout box terminal B2) for an open circuit, a short to supply voltage and a short to ground. See Figure. Repair as necessary and go to next step.
If wiring and connectors are okay, try a new rear heated oxygen sensor. See REMOVAL, OVERHAUL & INSTALLATION - EXCEPT S40 & V40 article. Go to next step.
After completing repair, ensure all electrical connectors and components are correctly installed. Connect a scan tool.
Perform a test drive as follows:
- Turn A/C on.
- Drive vehicle so that idle, normal and high speeds are reached. Operate vehicle in each range for approximately 5 minutes. Total drive time must be 15 minutes.
- For turbo models, accelerate at full throttle a number of times so that high boost pressure is reached.
- DO NOT shut engine off after completing test drive or test drive will have to be repeated.
Check if rear heated oxygen sensor DTC reset after test drive. If DTC has been eliminated, diagnosis is complete.