Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Test Procedure
- DW1 CHECK FOR DTCS
Are DTCs P0040, P0041, P0053, P0054, P0055, P0059, P0060, P0132, P0133, P0135, P0138, P0141, P0144, P0147, P0152, P0153, P0155, P0158, P0161, or P1127 present?
Yes No For DTCs P0040 or P0041, GO to DW2.
For DTCs P0053, P0054, P0055, P0059 or P0060, GO to DW13.
For DTCs P0132, P0138, P0144, P0152 or P0158, GO to DW19.
For DTCs P0133 or P0153, GO to DW3.
For DTCs P0135, P0141, P0147, P0155 or P0161, GO to DW9.
For DTC P1127, GO to DW18.For all others, GO to DIAGNOSTIC TROUBLE CODE (DTC) CHARTS AND DESCRIPTIONS . - DW2 KOER DTCS P0040 AND P0041: CROSSED SENSOR WIRES
- Key in OFF position.
- Check the vehicle repair history.
- Verify the HO2S connectors are connected to the correct engine bank.
Is a concern present?
Yes No REPAIR as necessary. Unable to duplicate or identify the concern at this time. CLEAR the DTCs. REPEAT the self-test. GO to Pinpoint Test Z . - DW3 CONTINUOUS MEMORY DTCS P0133 AND P0153: CARRY OUT THE KOER SELF-TEST
- Engine at normal operating temperature.
- Carry out the KOER self-test.
Are DTCs P0040, P0041 or P1127 present?
Yes No DISREGARD the current diagnostic trouble code (DTC) at this time. DIAGNOSE the next DTC. GO to DIAGNOSTIC TROUBLE CODE (DTC) CHARTS AND DESCRIPTIONS . GO to DW4. - DW4 CHECK THE HO2S RESPONSE TEST RESULTS
- Key ON, engine OFF.
- Access the diagnostic monitoring test results for the HO2S11 and HO2S21.
Is the indicated value greater than the minimum threshold?
Yes No CLEAR the DTCs.
GO to DW3.GO to DW5. - DW5 CHECK FOR UNMETERED AIR LEAKS NOTE: Fuel calculations can be affected by unmetered air leaks.
- Carefully inspect the following areas for potential air leaks:
- hoses connecting to the mass air flow (MAF) sensor assembly
- hoses connecting to the throttle body
- intake manifold gasket leaks
- PCV system
- the vacuum lines are disconnected
- improperly seated engine oil dipstick, tube or oil fill cap
- exhaust leaks at flanges and gaskets
Are any air leaks present?
Yes No REPAIR the source of the air leak. RESET the keep alive memory (KAM). REFER to RESETTING THE KEEP ALIVE MEMORY (KAM) .
REPEAT the self-test.GO to DW6. - Carefully inspect the following areas for potential air leaks:
- DW6 CHECK THE HO2S CIRCUIT CONTINUITY NOTE: HO2S is displayed as O2S on the diagnostic tool.
- HO2S connector disconnected.
- Check the connector (both halves) for any water contamination.
- Connect a 5 amp fused jumper wire between the following:
Point A HO2S Connector, Harness Side Point B HO2S Connector, Harness Side HO2S Signal VPWR - Key ON, engine running.
- Access the PCM and monitor the HO2S Signal PID.
Is the voltage greater than 1 V?
Yes No INSTALL a new HO2S. REFER to the appropriate ELECTRONIC ENGINE CONTROLS article .
CHANGE the engine oil and oil filter.
RESET the keep alive memory (KAM). REFER to RESETTING THE KEEP ALIVE MEMORY (KAM) .
REPEAT the self-test.GO to DW7. - DW7 CHECK THE HO2S CIRCUIT(S) FOR AN OPEN IN THE HARNESS NOTE: A vehicle hoist may be required to access the HO2S harness.
- Key in OFF position.
- Remove the jumper wire(s).
- Visually inspect the HO2S harness for exposed wiring, water contamination, corrosion, and proper assembly.
- PCM connector disconnected.
- Measure the resistance between:
( + ) PCM Connector, Harness Side ( - ) HO2S Connector, Harness Side HO2S Signal HO2S Signal SIGRTN SIGRTN
Are the resistances less than 5 ohms?
Yes No GO to DW8. REPAIR the open circuit. CLEAR the DTCs.
REPEAT the self-test. - DW8 CHECK THE HO2S CIRCUIT FOR A SHORT TO VPWR IN THE HARNESS
- Measure the resistance between:
( + ) PCM Connector, Harness Side ( - ) PCM Connector, Harness Side HO2S Signal VPWR
Is the resistance greater than 10K ohms?
Yes No GO to DW9. GO to DW11. - Measure the resistance between:
- DW9 DTCS P0135, P0141, P0147, P0155 OR P0161: CHECK FOR A SOURCE OF POTENTIAL HO2S CONTAMINATION
- Investigate the following items as potential sources of HO2S contamination:
- use of unapproved silicon sealers
- fuel contaminated by silicon additives
- excessive oil consumption
- glycol leaking internally in the engine
- lead-contaminated fuel
- short drive cycles in cold weather
- use of unapproved cleaning agents
Is a concern present?
Yes No REPAIR the source of the contamination.
CHANGE the engine oil and oil filter.
RESET the keep alive memory (KAM). REFER to RESETTING THE KEEP ALIVE MEMORY (KAM) .
REPEAT the self-test.GO to DW10. - Investigate the following items as potential sources of HO2S contamination:
- DW10 VISUALLY INSPECT THE HO2S HARNESS
- PCM connector connected.
- Visually inspect the HO2S harness for exposed wiring, water contamination, corrosion, and proper assembly.
Is a concern present?
Yes No REPAIR as necessary.
CLEAR the DTCs. REPEAT the self-test.GO to DW11. - DW11 CHECK THE HO2S AND SIGRTN CIRCUITS FOR AN OPEN IN THE HARNESS NOTE: Verify the harness pins are in the proper location.
- Measure the resistance between:
( + ) PCM Connector, Harness Side ( - ) HO2S Connector, Harness Side HO2S Signal HO2S Signal SIGRTN SIGRTN
Are the resistances less than 5 ohms?
Yes No GO to DW12. REPAIR as necessary.
CLEAR the DTCs. REPEAT the self-test. - Measure the resistance between:
- DW12 CARRY OUT THE KOEO ON DEMAND SELF-TEST
- Key ON, engine OFF.
- Check for KOEO DTCs.
Are DTCs P0135, P0141, P0147, P0155 or P0161 present?
Yes No GO to DW13. GO to DW14. - DW13 DTCS P0053, P0054, P0055, P0059 AND P0060: CHECK FOR VPWR IN THE HARNESS NOTE: If DTCs P0053, P0054, P0055, P0059, or P0060 are present, test their related circuits individually.
- Key in OFF position.
- HO2S connector disconnected.
- Key ON, engine OFF.
- Measure the voltage between:
( + ) HO2S Connector, Harness Side ( - ) HO2S Connector, Harness Side VPWR SIGRTN
Is the voltage greater than 10 V?
Yes No GO to DW14. REPAIR the open circuit. CHECK the fuses.
CLEAR the DTCs. REPEAT the self-test. - DW14 CHECK THE HO2S HEATER FOR SHORTS IN THE HARNESS NOTE: If DTCs P0053, P0054, P0055, P0059, or P0060 are present, test their related circuits individually.
- Key in OFF position.
- HO2S connector disconnected.
- PCM connector disconnected.
- Measure the resistance between:
( + ) HO2S Connector, Harness Side ( - ) Vehicle Battery HO2S Heater Negative terminal - Measure the resistance between:
( + ) HO2S Connector, Harness Side ( - ) HO2S Connector, Harness Side HO2S Heater VPWR HO2S Heater SIGRTN HO2S Heater HO2S Signal
Are the resistances greater than 10K ohms?
Yes No GO to DW15. REPAIR the short circuit. CLEAR the DTCs.
REPEAT the self-test. - DW15 CHECK THE HO2S HEATER CIRCUIT FOR AN OPEN IN THE HARNESS
- Measure the resistance between:
( + ) PCM Connector, Harness Side ( - ) HO2S Connector, Harness Side HO2S Heater HO2S Heater
Is the resistance less than 5 ohms?
Yes No GO to DW16. REPAIR the open circuit. CLEAR the DTCs.
REPEAT the self-test. - Measure the resistance between:
- DW16 CHECK THE INTERNAL RESISTANCE OF THE HO2S HEATER
- Measure the resistance between:
( + ) HO2S Connector, Component Side ( - ) HO2S Connector, Component Side HO2S Heater VPWR
Is the resistance between 3 - 30 ohms?
Yes No GO to DW17. INSTALL a new HO2S. REFER to the appropriate ELECTRONIC ENGINE CONTROLS article .
RESET the keep alive memory (KAM). REFER to RESETTING THE KEEP ALIVE MEMORY (KAM) .
REPEAT the self-test. - Measure the resistance between:
- DW17 CHECK THE HO2S HEATER CIRCUIT FOR AN INTERNAL SHORT TO SIGRTN OR GND
- Measure the resistance between:
( + ) HO2S Connector, Component Side ( - ) HO2S Connector, Component Side HO2S Heater SIGRTN - Measure the resistance between:
( + ) HO2S Connector, Component Side ( - ) Vehicle Battery HO2S Heater Negative terminal
Is the resistance greater than 10K ohms?
Yes No GO to DW24. INSTALL a new HO2S. REFER to the appropriate ELECTRONIC ENGINE CONTROLS article .
RESET the keep alive memory (KAM). REFER to RESETTING THE KEEP ALIVE MEMORY (KAM) .
REPEAT the self-test. - Measure the resistance between:
- DW18 KOER DTC P1127: EXHAUST TEMPERATURE OUT OF RANGE NOTE: Address all other DTCs before proceeding.
- Key ON, engine running.
- Engine at normal operating temperature.
- Access the PCM and monitor the HO2S Heater PID.
Is the PID state ON?
Yes No CARRY OUT the KOER self-test. RUN the engine until the PID indicates ON.
CARRY OUT the KOER self-test. - DW19 DTCS P0132, P0138, P0144, P0152 AND P0158: VISUALLY INSPECT THE HO2S HARNESS NOTE: Disconnect the suspect HO2S harness connector. Only the suspect HO2S needs to be diagnosed.
- Key in OFF position.
- HO2S connector disconnected.
- Visually inspect the HO2S harness.
- check the connector (both halves) for contamination
- make sure the connector pins are fully seated
Is a concern present?
Yes No REPAIR as necessary.
CLEAR the DTCs. REPEAT the self-test.GO to DW20. - DW20 CHECK THE HO2S SIGNAL LEVEL TOO HIGH
- HO2S connector connected.
- Key ON, engine running.
- Access the PCM and monitor the HO2S Signal PID.
Is the voltage less than 1.1 V?
Yes No GO to DW21. GO to DW22. - DW21 CARRY OUT A THOROUGH WIGGLE TEST ON THE HO2S HARNESS
- Key in OFF position.
- Key ON, engine OFF.
- Access the PCM and monitor the HO2S Signal PID.
- Carry out a thorough wiggle test on the HO2S harness.
Does the voltage change during the wiggle test?
Yes No REPAIR as necessary.
CLEAR the DTCs. REPEAT the self-test.GO to Pinpoint Test Z . - DW22 CHECK THE HO2S SIGNAL FOR A SHORT TO VPWR INSIDE THE SENSOR
- Key in OFF position.
- HO2S connector disconnected.
- Key ON, engine running.
- Access the PCM and monitor the HO2S Signal PID.
Is the voltage less than 1.1 V?
Yes No INSTALL a new HO2S. REFER to the appropriate ELECTRONIC ENGINE CONTROLS article .
RESET the keep alive memory (KAM). REFER to RESETTING THE KEEP ALIVE MEMORY (KAM) .
REPEAT the self-test.GO to DW23. - DW23 CHECK THE HO2S CIRCUIT FOR A SHORT TO VPWR IN THE HARNESS
- Key in OFF position.
- PCM connector disconnected.
- Key ON, engine OFF.
- Measure the voltage between:
( + ) HO2S Connector, Harness Side ( - ) HO2S Signal Ground
Is any voltage present?
Yes No REPAIR the short circuit. CLEAR the DTCs.
REPEAT the self-test.GO to DW24. - DW24 CHECK FOR CORRECT PCM OPERATION
- Disconnect all the PCM connectors.
- Visually inspect for:
- pushed out pins
- corrosion
- Connect all the PCM connectors and make sure they seat correctly.
- Carry out the PCM self-test and verify the concern is still present.
Is the concern still present?
Yes No INSTALL a new PCM. REFER to FLASH ELECTRICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY (EEPROM) . The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.