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Heated Oxygen Sensor (Ho2S) Heater Circuit

DTC P0135, P0141, P0155 DETECTION CONDITION AND POSSIBLE CAUSE

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 PCM.
HINT  HO2S Heater Description 
  • Heats the HO2S sensor to temperatures of -1400 F (800 C).
  • VPWR circuit supplies voltage to the heater with the PCM completing the ground when the proper conditions occur.
G03988118Courtesy of MAZDA MOTORS CORP.
DTC P0135, P0141, P0155 INSPECTION

STEP INSPECTION ACTION
1
  • Was 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 TEST 4: INTERMITTENT with all HO2S PIDs.
Otherwise, go to next step.
No Perform PCM Quick Test.
2 VISUAL INSPECTION
  • Visually inspect the suspect HO2S circuit for exposed wiring, contamination, corrosion and proper assembly.
  • Were any concerns found during the visual inspection? 
 Yes Repair any concerns found during visual inspection.
Go to step 8.
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.
No Check fuse 13 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.
  • Is the resistance between 3 and 30 ohms? 
 Yes Go to next step.
No Replace HO2S.
See HEATED OXYGEN SENSOR (HO2S) in REMOVAL, OVERHAUL, AND INSTALLATION article in Engine Performance .
Go to step 8.
5 CHECK FOR HEATER GND AND VPWR SHORTED TO HO2S CASE
  • Measure resistance between HO2S HTR GND at the HO2S harness connector and the HO2S case.
  • Measure resistance between HO2S HTR GND and SIG RTN at the HO2S harness connector.
  • Measure resistance between VPWR at the HO2S harness connector and the HO2S case.
  • Is the resistance greater than 10K ohms? 
 Yes Go to next step.
No Replace HO2S.
See HEATED OXYGEN SENSOR (HO2S) in REMOVAL, OVERHAUL, AND INSTALLATION article in Engine Performance .
Go to step 8.
6 CHECK FOR SHORTS TO OTHER GROUNDS AND VPWR IN THE HO2S HEATER GROUND HARNESS CIRCUITS
  • Disconnect NGS Tester from DLC.
  • 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.
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 of the heater circuit in the PCM.
Replace PCM. See COMPUTERIZED ENGINE CONTROLS .
Go to step 8.
No Repair open or excessive resistance of heater circuit in harness.
Go to step 8.
8 VERIFY TROUBLESHOOTING OF DTCs COMPLETED
  • Make sure to reconnect all disconnected connectors.
  • Clear DTCs from PCM memory using NGS tester generic OBD-II function.
  • Perform PCM Quick Test.
  • Is same DTC present? 
 Yes Replace PCM. See COMPUTERIZED ENGINE CONTROLS .
Repeat PCM Quick Test.
No If any other DTC is present, go to applicable DTC inspection.
If no DTC is present, troubleshooting complete.
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