Check HO2S for poor connection or loose terminal.

Check if HO2S is securely installed.

Is HO2S in good condition?

	▶ Go to "Check the Signal waveform of HO2S" as follows.
	▶ Repair it and then go to "Verification of Vehicle Repair" procedure.

IG "OFF". Connect HO2S connector.

Engine start.

With engine at operating temperature, monitor signal waveform of HO2S with GDS.

Fig.1) Normal waveforms of front HO2S(the upper) and rear HO2S(the lower) (chassis ground used)

Fig.2) Normal waveforms of front HO2S(the upper) and rear HO2S(the lower) (sensor ground used)

Is the sensor switching properly?

	▶ Substitute with a known - good PCM and check for proper operation. If the problem is corrected, replace PCM and go to "Verification of Vehicle Repair" procedure.
	▶ Substitute with a known - good HO2S and check for proper operation. If the problem is corrected, go to "Verification of Vehicle Repair" procedure.