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 P0133: A/F Sensor (Sensor 1) Malfunction/Slow Response
- Turn the ignition switch to ON (II).
- Clear the DTC with the HDS.
- Start the engine. Hold the engine speed at 3, 000 rpm without load (in P or N) until the radiator fan comes on, then let it idle.
- Test-drive under these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 158°F(70°C)
- Transmission in D
- Drive the vehicle at 25 mph (40 km/h) or less for 5 minutes, then drive at a steady speed of 32 mph (52 km/h) or more
- Monitor the OBD STATUS for DTC P0133 in the DTCs MENU with the HDS.
Does the screen indicate FAILED?
YES -Go to step 6.
NO -If the screen indicates PASSED, intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the A/F sensor (Sensor 1) and the PCM. If the screen indicates EXECUTING, keep driving until a result comes on. If the screen indicates OUT OF CONDITION or NOT COMPLETED, go to step 3 and recheck.
- Turn the ignition switch to LOCK (0).
- Replace the A/F sensor (Sensor 1) (see A/F SENSOR REPLACEMENT ).
- Turn the ignition switch to ON (II).
- Reset the PCM with the HDS.
- Do the PCM idle learn procedure (see PCM IDLE LEARN PROCEDURE ).
- Start the engine. Hold the engine speed at 3, 000 rpm without load (in P or N) until the radiator fan comes on, then let it idle.
- Test-drive under these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 158°F(70°C)
- Transmission in D
- Drive the vehicle at 25 mph (40 km/h) or less for 5 minutes, then drive at a steady speed of 32 mph (52 km/h) or more
- Check for Pending or Confirmed DTCs with the HDS.
Is DTC P0133 indicated?
YES -Check for poor connections or loose terminals at the A/F sensor (Sensor 1) and the PCM, then go to step 1.
NO -Go to step 14.
- Monitor the OBD STATUS for DTC P0133 in the DTCs MENU with the HDS.
Does the screen indicate PASSED?
YES -Troubleshooting is complete. If any other Pending or Confirmed DTCs were indicated in step 13, go to the indicated DTC's troubleshooting.
NO -If the screen indicates FAILED, check for poor connections or loose terminals at the A/F sensor (Sensor 1) and the PCM, then go to step 1. If the screen indicates EXECUTING, keep driving until a result comes on. If the screen indicates OUT OF CONDITION or NOT COMPLETED, go to step 11.
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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.