HF2 - Check For HO2S Monitor DTCs

*** THIS ARTICLE REFLECTS CHANGES MADE BY TSB # 9326B7, December 1993

NOTE 1:
Incorrect HO2S signal input (e.g. rich/lean input signal when the engine is operating under lean/rich conditions) may cause an abnormal temperature increase in the catalyst.

NOTE 2:
Non-California applications will not have an active HO2S monitor. As a result, a Catalyst Efficiency Monitor DTC can be generated for a rear HO2S concern. To check for a rear HO2S concern on these applications, go to the HO2S monitor Pinpoint Test Step H82. H82 - Check For Crossed HO2S Harness Connector

If any repair actions are necessary in Pinpoint Test H, run KOER Self-Test, to verify the repair. Diagnostic Subroutines (DSR) - Extracting Codes

Otherwise, go to HF3. HF3 - Check For ECT Sensor DTCs

- Were any of the following HO2S monitor DTCs recorded in HF1: 0136, 0138, 0140 and 0141 (Bank 1, rear HO2S) or 0156, 0158, 0160 and 0161 (Bank 2, rear HO2S)?

YES -- GO to Powertrain Diagnostic Charts, to address the HO2S Monitor DTCs. [1][2]Diagnostic Trouble Code (DTC) Charts

NO -- GO to HF3. HF3 - Check For ECT Sensor DTCs