Heated Oxygen Sensor (Ho2S)

NOTE: The following test procedures are for DTCs P0131 and P0151.

Fig 1: Identifying Heated Oxygen Sensor (Ho2S)

Courtesy of MAZDA MOTORS CORP.

Fig 2: Identifying Heating Oxyzen Sensor

Courtesy of MAZDA MOTORS CORP.

HEATING OXYZEN 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	CHECK FOR SOURCE OF POTENTIAL HO2S CONTAMINATION Check for HO2S contamination, such as: Use of unapproved silicon sealers. Fuel contaminated by silicon additives. Excessive oil burning (rings, valve seals, oil overfill). Glycol leaking internally in the engine. Lead-contaminated fuel. Short drive cycles in cold weather. Use of unapproved cleaning agents. Are there any concerns?	Yes	Repair the source of contamination. Change engine oil filter. Reset Keep Alive Random Access Memory (RAM) by disconnecting the battery for 2 minutes, then reconnecting the battery.
2		No	Go to next step.
3	VERIFY WIRING IS IN PROPER PIN LOCATION Disconnect PCM. Install Breakout Box, leave PCM disconnected. Measure resistance of the HO2S SIG circuit between PCM test pin E49 (DTC P0131) or PCM test pin E48 (DTC P0151) and the HO2S sensor harness connector. Measure resistance of the SIG RTN circuit between PCM test pin E41 and the HO2S sensor harness connector. Is each resistance less than 5.0 ohms?	Yes	Replace sensor. See HEATED OXYGEN SENSOR (HO2S) AND CATALYST MONITOR SENSOR - 2.3L , HEATED OXYGEN SENSOR (HO2S) AND CATALYST MONITOR SENSOR - 3.0L (4V) . Go to next step.
3		No	Repair wiring as necessary. Go to next step.
4	VERIFY TROUBLESHOOTING OF DTCs COMPLETED Make sure to reconnect all disconnected connectors. Clear DTCs from PCM memory using WDS or equivalent tester generic OBD If 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 .
4		No	If any other DTC is present, go to applicable DTC inspection. If no DTC is present, troubleshooting complete.