Heated Oxygen Sensor (Ho2S)

DTC P0131, P0151 DETECTION CONDITION & POSSIBLE CAUSES

DTC P0131, P0151	HEATED OXYGEN SENSOR (HO2S)
DETECTION CONDITION	P0131 indicates HO2S-11 (front RH) has generated a negative voltage. P0151 indicates HO2S-21 (front LH) has generated a negative voltage.
POSSIBLE CAUSE	Contaminated HO2S (water, fuel etc.) Crossed HO2S signal/signal return wiring
HINT	HO2S Description Detects the presence of oxygen in the exhaust and produces a variable voltage (0.0-1.1 V) according to the amount of oxygen detected. A high concentration of oxygen (lean air/fuel ratio) in the exhaust produces a low voltage signal (less than 0.4 V) A low concentration of oxygen (rich air/fuel ratio) in the exhaust produces a high voltage signal (greater than 0.6 V) Provides feedback to the powertrain control module (PCM) indicating air/fuel ratio in order to achieve a near stoichiometric air/fuel ratio of 14.7:1 during closed loop engine operation.
Courtesy of MAZDA MOTORS CORP.
Courtesy of MAZDA MOTORS CORP.
Courtesy of MAZDA MOTORS CORP.

DTC P0131, P0151 DIAGNOSTIC PROCEDURE

DTC P0131, P0151		HEATED OXYGEN SENSOR (HO2S)
STEP	INSPECTION		ACTION
1	Was the PCM quick test performed?	Yes	Go to next step.
1	Was the PCM quick test performed?	No	Perform PCM quick test. See PCM QUICK TEST .
2	DTCS P0131 AND P0151: CONTAMINATED HO2S/VOLTAGE SHIFT NOTE: CP0131=HO2S-11 (Front RH) and DTC P0151 = HO2S-21 (Front LH). Check for water in HO2S connector. Is there water in the HO2S connector?	Yes	Repair source of water entry. Dry out connector. Replace sensor. See HEATED OXYGEN SENSOR (HO2S) REMOVAL / INSTALLATION . Go to step 4.
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 60 (DTC P0131) or PCM test pin 87 (DTC P0151) and the HO2S harness connector. Measure resistance of the SIG RTN circuit between PCM test pin 71/97 and the HO2S harness connector. Is each resistance less than 5.0 ohms?	Yes	Replace sensor. See HEATED OXYGEN SENSOR (HO2S) REMOVAL / INSTALLATION . Go to next step.
3		No	Repair wiring as necessary. Go to next step.
4	VERIFY TROUBLESHOOTING OF DTCs COMPLETED Connect all disconnected connectors. Clear DTCs from PCM memory using WDS or equivalent tester. Perform PCM quick test. Is the same DTC present?	Yes	Replace PCM. See POWERTRAIN CONTROL MODULE (PCM) REMOVAL / INSTALLATION . Repeat PCM quick test.
4		No	If any other DTC is present, go to applicable DTC inspection. See DIAGNOSTIC TROUBLE CODE (DTC) INDEX - POWERTRAIN CONTROL MODULE (PCM) . If no DTC is present, troubleshooting is complete.

DTC P0136, P1137, P1138 DETECTION CONDITION & POSSIBLE CAUSES

DTC P0136, P1137, P1138	HEATED OXYGEN SENSOR (HO2S)
DETECTION CONDITION	P0136 indicates the output voltage of the rear HO2S fails to meet the calibrated limits (Bank 1). P1137 and P1138 indicate the rear HO2S is forced rich and lean by the powertrain control module (PCM). The test fails if the PCM does not detect the rich signal (P1137) or lean signal (P1138) during KOER self-test.
POSSIBLE CAUSE	Wiring concerns: Pinched, shorted, and corroded wiring and pins Crossed sensor wires Other concerns: Exhaust leaks Contaminated or damaged sensor
HINT	HO2S Description Detects the presence of oxygen in the exhaust and produces a variable voltage (0.0-1.1 V) according to the amount of oxygen detected. A high concentration of oxygen (lean air/fuel ratio) in the exhaust produces a low voltage signal (less than 0.4 V) A low concentration of oxygen (rich air/fuel ratio) in the exhaust produces a high voltage signal (greater than 0.6 V) Provides feedback to the PCM indicating air/fuel ratio in order to achieve a near stoichiometric air/fuel ratio of 14.7:1 during closed loop engine operation.
Courtesy of MAZDA MOTORS CORP.
Courtesy of MAZDA MOTORS CORP.

DTC P0136, P1137, P1138 DIAGNOSTIC PROCEDURE

DTC P0136, P1137, P1138		HEATED 0XYGEN SENSOR (HO2S)
STEP	INSPECTION		ACTION
1	Was the PCM quick test performed?	Yes	if continuous memory ignition P0350-P0354 DTCs are received, See INTEGRATED IGNITION COIL 1, 2, 3, OR 4 FAILURE . If misfire P0300-P0306 DTCs are received, See MISFIRE DETECTION MONITOR . For other misfire DTCs, repair them first. Otherwise, Go to next step.
1	Was the PCM quick test performed?	No	Perform PCM Quick Test. See PCM QUICK TEST .
2	CHECK FOR HO2S KOER Are DTCs P1137 or P1138 present during PCM Quick Test?	Yes	Go to next step.
2		No	The fault that produced DTC P0136 is intermittent. See GENERAL PINPOINT TEST 4: INTERMITTENT .
3	VISUAL INSPECTION Checked for pinched, corroded and/or stretched wires. NOTE: Any exhaust leaks between the engine and the end of the catalyst can cause DTC P0136 or P0156 with P1137 and/or P1138. Inspect the following: Check for punctures and cracks in catalyst and pipes leading to them Check exhaust flanges for leaks Check HO2S torque Are any of the listed possible causes present?	Yes	Repair as necessary. Go to step 10.
3		No	Go to next step.
4	CHECK HO2S HARNESS FOR SHORT TO VPWR AND GROUND Disconnect WDS or equivalent tester. Disconnect PCM. Install breakout box, leave PCM disconnected. Disconnect rear HO2S. Measure resistance between PCM test pin 35 and the following PCM test pins: 71 or 97 (short to VPWR or SIG RTN) 90 (short to VREF) 103 (short to PWRGND) Is each resistance greater than 10K ohms?	Yes	Go to next step.
4		No	Repair short in harness. Go to step 10.
5	CHECK RESISTANCE OF HO2S SIG AND GROUND CIRCUITS FOR OPEN IN HARNESS Measure resistance of HO2S SIG circuit between PCM test pin 35 and the HO2S harness connector. Measure resistance of HO2S SIG RTN / VPWR circuit between PCM test pin 71 or 97 and the HO2S harness connector. Is each resistance reading less than 5.0 ohms?	Yes	Go to next step.
5		No	Repair open circuit. Go to step 10.
6	CHECK HO2S CIRCUIT VOLTAGE Remove breakout box. Connect PCM and rear HO2S. Connect WDS or equivalent tester. Key on, engine off (KOEO). Access the O2S12 PID with WDS or equivalent tester and note the voltage. Is the voltage greater than 1.5 V?	Yes	Go to step 9.
6		No	Go to next step.
7	CHECK RESISTANCE OF HO2S GROUND CIRCUIT IN THE PCM Key OFF. Disconnect PCM. Install breakout box and connect PCM to breakout box. Leave vehicle harness disconnected from breakout box. Measure resistance between PCM test pins 71 or 97 (SIG RTN) and PCM test pin 103(PWRGND). Is the resistance less than 5.0 ohms?	Yes	Go to next step.
7		No	Replace PCM. See POWERTRAIN CONTROL MODULE (PCM) REMOVAL / INSTALLATION . Go to step 10.
8	APPLY 12 VOLTS TO SUSPECT HO2S CIRCUIT Remove breakout box. Connect PCM. Disconnect rear HO2S. Jumper VPWR to HO2S SIG at the vehicle harness connector. Key on, engine off (KOEO). Access O2S12 PID and monitor. Is the PID value greater than 1.5 V?	Yes	Replace rear HO2S. See HEATED OXYGEN SENSOR (HO2S) REMOVAL / INSTALLATION . Go to step 10.
8		No	Replace PCM. See POWERTRAIN CONTROL MODULE (PCM) REMOVAL / INSTALLATION . Go to step 10.
9	CHECK FOR OVER VOLTAGE ON THE HO2S CIRCUIT IN THE PCM Disconnect rear HO2S. Key on, engine off (KOEO). Measure voltage between SIG RTN circuit at the HO2S vehicle harness connector and battery negative post. Measure voltage between HO2S SIG circuit at the HO2S vehicle harness connector and battery negative post. Are the voltage readings greater than 1.5 V?	Yes	Replace PCM. See POWERTRAIN CONTROL MODULE (PCM) REMOVAL / INSTALLATION . Go to next step.
9		No	Replace rear HO2S. See HEATED OXYGEN SENSOR (HO2S) REMOVAL / INSTALLATION . Go to next step.
10	VERIFY TROUBLESHOOTING OF DTCs COMPLETED Connect all disconnected connectors. Clear DTCs from PCM memory using WDS or equivalent tester. Perform PCM quick test. Is same DTC present?	Yes	Replace PCM. See POWERTRAIN CONTROL MODULE (PCM) REMOVAL / INSTALLATION . Repeat PCM quick test.
10		No	If any other DTC is present, go to applicable DTC inspection. See DIAGNOSTIC TROUBLE CODE (DTC) INDEX - POWERTRAIN CONTROL MODULE (PCM) . If no DTC is present, troubleshooting is complete.