Heated Oxygen Sensor (Ho2S) Signals

NOTE: The following test procedures are for DTCs P0040, P0041, P1128 and P1129.

Fig 1: Heated Oxygen Sensor (HO2S) Signals Detection Condition Possible Cause

Courtesy of MAZDA MOTORS CORP.

Fig 2: Identifying Heated Oxygen Sensor (Ho2S) Signals

Courtesy of MAZDA MOTORS CORP.

HEATED OXYGEN SENSOR INSPECTION/ACTION CHART

STEP	INSPECTION		ACTION
1	Was PCM Quick Test performed?	Yes	Go to next step.
1	Was PCM Quick Test performed?	No	Perform PCM Quick Test. See PCM QUICK TEST .
2	INSPECT HO2S HARNESS CONNECTORS For P0040 or P1128, visually inspect vehicle upstream HO2S harness connector(s) for any indication of being crossed (stretched wires, wire harnesses not mounted properly). For P0041 or P1129, visually inspect vehicle downstream HO2S harness connector(s) for any indication of being crossed (stretched wires, wire harnesses not mounted properly). Are there crossed connections or wires?	Yes	Repair as necessary. Go to next step.
2		No	Go to next step.
3	VERIFY TROUBLESHOOTING OF DTCs COMPLETED Make sure to reconnect all disconnected connectors. Clear DTCs from PCM memory using WDS or equivalent tester generic OBD II function. Perform PCM Quick Test. See PCM QUICK TEST . Is same DTC present?	Yes	Replace PCM. See POWERTRAIN CONTROL MODULE (PCM) . Repeat PCM Quick Test. See PCM QUICK TEST .
3		No	If any other DTC is present, go to DIAGNOSTIC TROUBLE CODE NUMBERS . If no DTC is present, troubleshooting complete.