H55 - Check HO2S For Short to Ground

- Key Off.

- Breakout box installed, PCM disconnected.

- HO2S connected.

- Measure resistance between PWR GND/SIG RTN test Pin and HO2S Signal Test Pin at the breakout box.

HO2S-11 SIG = Test Pin 60
HO2S-21 SIG = Test Pin 87
HO2S PWR GND = Test Pin 24, 76 and 103
HO2S SIG RTN = Test Pin 91

- Is resistance greater than 10,000 ohms?

YES -- For DTCs 1131C, 1151C, 1130 and 1150: Go to H61. H61 - HO2S Check

For other HO2S DTCs: REMOVE breakout box. RECONNECT HO2S. REPLACE PCM.

NO -- REPLACE HO2S. REMOVE breakout box. RECONNECT PCM. DRIVE 5 miles/55 mph. Rerun quick test. Diagnostic Subroutines (DSR) - Extracting Codes