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.
DTC Diagnosis Procedure
- CHECK GROUND CONNECTION
- Turn ignition switch OFF.
- Check ground connection M11, M95. Refer to Ground Inspection in Circuit Inspection .
Is the inspection result normal?
YES
GO TO 2.
NO
Repair or replace ground connection.
- CLEAR THE MIXTURE RATIO SELF-LEARNING VALUE
- Clear the mixture ratio self-learning value. Refer to Description .
- Run engine for at least 10 minutes at idle speed.
Is the 1st trip DTC P0171 or P0174 detected? Is it difficult to start engine?
YES
Perform trouble diagnosis for DTC P0171 or P0174. Refer to DTC Logic .
NO
GO TO 3.
- CHECK HO2S2 GROUND CIRCUIT FOR OPEN AND SHORT
- Turn ignition switch OFF.
- Disconnect heated oxygen sensor 2 (HO2S2) harness connector.
- Disconnect ECM harness connector.
- Check the continuity between HO2S2 harness connector and ECM harness connector.
DTC
HO2S2
ECM
Continuity
Bank
Connector
Terminal
Connector
Terminal
P2271
1
F79
1
F128
35
Existed
- Also check harness for short to ground and short to power.
Is the inspection result normal?
YES
GO TO 4.
NO
Repair open circuit, short to ground or short to power in harness or connectors.
- CHECK HO2S2 INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
- Check the continuity between HO2S2 harness connector and ECM harness connector.
DTC
HO2S2
ECM
Continuity
Bank
Connector
Terminal
Connector
Terminal
P2271
1
F79
4
F128
41
Existed
- Check the continuity between HO2S2 harness connector and ground, or ECM harness connector and ground.
DTC
HO2S2
Ground
Continuity
Bank
Connector
Terminal
P2271
1
F79
4
Ground
Not existed
DTC
ECM
Ground
Continuity
Bank
Connector
Terminal
P2271
1
F128
41
Ground
Not existed
- Also check harness for short to power.
Is the inspection result normal?
YES
GO TO 5.
NO
Repair open circuit, short to ground or short to power in harness or connectors.
- Check the continuity between HO2S2 harness connector and ECM harness connector.
- CHECK HEATED OXYGEN SENSOR 2
Refer to Component Inspection .
Is the inspection result normal?
YES
GO TO 7.
NO
GO TO 6.
- REPLACE HEATED OXYGEN SENSOR 2
Replace malfunctioning heated oxygen sensor 2.
CAUTION:- Discard any heated oxygen sensor which has been dropped from a height of more than 0.5 m (19.7 in) onto a hard surface such as a concrete floor; use a new one.
- Before installing new heated oxygen sensor, clean exhaust system threads using Oxygen Sensor Thread Cleaner [commercial service tool (J-43897-18 or J-43897-12)] and approved Anti-seize Lubricant (commercial service tool).
INSPECTION END
- CHECK INTERMITTENT INCIDENT
Refer to Intermittent Incident .
INSPECTION END
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.