H25 - Check For Short In HO2S Circuit

- Key Off.

- Breakout box installed. PCM disconnected.

- Measure the resistance between the HO2S Signal Test Pin and VPWR circuit and HO2S Signal Test Pin and Signal return circuit.
- HO2S-11 = SIG. Pin 60
- HO2S-21 = SIG. Pin 87
- VPWR = 71/97
- Signal RTN = 91

- Is the resistance greater than 10,000 ohms?

YES -- PCM is at fault. REPLACE PCM. COMPLETE a HO2S monitor drive cycle.

NO -- SERVICE short circuit. REMOVE breakout box. RECONNECT all components. COMPLETE a HO2S monitor drive cycle.