Heated Oxygen Sensor (Ho2S) Heater Circuit

DTC P0135, P0141, P0155 DETECTION CONDITION & POSSIBLE CAUSES

DTC P0135, P0141, P0155	HEATED OXYGEN SENSOR (HO2S) HEATER CIRCUIT
DETECTION CONDITION	P0135 indicates HO2S-11 (front RH) heater circuit is open, shorted to ground, shorted to VPWR or has low or high current draw. P0141 indicates HO2S-12 (rear) heater circuit is open, shorted to ground, shorted to VPWR or has low or high current draw. P0155 indicates HO2S-21 (front LH) heater circuit is open, shorted to ground, shorted to VPWR or has low or high current draw.
POSSIBLE CAUSE	Shorts to VPWR in harness or HO2S Water in connectors Open VPWR circuit Open GND circuit Low battery voltage Corrosion or poor mating materials and wiring Damaged HO2S heater Damaged powertrain control module (PCM)
HINT	HO2S Heater Description Heats the HO2S to temperatures of 800°C (1, 472°F). VPWR circuit supplies voltage to the heater with the PCM completing the ground when the proper conditions occur.
Courtesy of MAZDA MOTORS CORP.
Courtesy of MAZDA MOTORS CORP.
Courtesy of MAZDA MOTORS CORP.
Courtesy of MAZDA MOTORS CORP.

DTC P0135 P0141, P0155 DIAGNOSTIC PROCEDURE

DTC P0135 P0141, P0155		HEATED OXYGEN SENSOR (HO2S) HEATER CIRCUIT
STEP	INSPECTION		ACTION
1	Was the PCM quick test performed?	Yes	If KOEO or KOER DTC P0135, P0141 and P0155 were not present during PCM quick test, fault may be intermittent. See GENERAL PINPOINT TEST 4: INTERMITTENT . Otherwise, Go to next step.
1	Was the PCM quick test performed?	No	Perform PCM Quick Test. See PCM QUICK TEST .
2	VISUAL INSPECTION Visually inspect the suspect HO2S circuit for exposed wiring, contamination, corrosion and proper assembly. Are any concerns found during the visual inspection?	Yes	Repair any concerns found during visual inspection. Go to step 8.
2		No	Go to next step.
3	CHECK FOR VPWR AT THE VEHICLE HARNESS CONNECTOR NOTE: If DTCs P0135 and P0155 or P0141 are displayed, both heater circuits will require testing. DTCs displayed separately are tested individually. Disconnect appropriate HO2S(s). Key on engine off (KOEO). Measure voltage between VPWR and SIG RTN at the suspect HO2S vehicle harness connector(s). Is the voltage greater than 10.5 V?	Yes	Go to next step.
3		No	Check fuse 41 in engine compartment fuse/relay box If fuse is OK, repair open circuit. Go to step 8.
4	CHECK HO2S HEATER RESISTANCE Measure resistance of the HO2S heater (R/W). Is the resistance between 3 and 30 ohms?	Yes	Go to next step.
4		No	Replace HO2S. See HEATED OXYGEN SENSOR (HO2S) REMOVAL / INSTALLATION . Go to step 8.
5	CHECK FOR HEATER GND AND VPWR SHORTED TO HO2S CASE Measure the resistance between the HO2S heater GND at the HO2S connector and the HO2S case. Measure the resistance between the HO2S heater GND and the SIG RTN pin at the HO2S. Measure the resistance between the HO2S VPWR at the HO2S connector and the HO2S case. Is each resistance greater than 10K ohms?	Yes	Go to next step.
5		No	Replace HO2S. See HEATED OXYGEN SENSOR (HO2S) REMOVAL / INSTALLATION . Go to step 8.
6	CHECK FOR SHORTS TO OTHER GROUNDS AND VPWR IN THE HO2S HEATER GROUND HARNESS CIRCUITS Disconnect WDS or equivalent tester. Disconnect PCM. Install breakout box, leave PCM disconnected. Use the following list to measure resistance between the appropriate PCM test pins: For DTC P0135, test pin 93 and test pins 103, 91 and 71 For DTC P0141, test pin 95 and test pins 103, 91 and 71 For DTC P0155, test pin 94 and test pins 103, 91 and 71 Is the resistance greater than 10K ohms?	Yes	Go to next step.
6		No	Repair short circuit. Go to step 8.
7	CHECK FOR OPEN HO2S HEATER GROUND HARNESS CIRCUIT Use the following list to measure the resistance between the appropriate PCM test pin (HTR GND) and the HO2S HTR GND at the vehicle harness connector: For DTC P0135, test pin 93 For DTC P0141, test pin 95 For DTC P0155, test pin 94 Is the resistance less than 4.0 ohms?	Yes	Open, shorted or excessive resistance in the heater circuit in the PCM. Replace PCM. See POWERTRAIN CONTROL MODULE (PCM) REMOVAL / INSTALLATION . Go to next step.
7		No	Repair open or excessive resistance in heater circuit in harness. Go to next step.
8	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.
8		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.