DTC EFI-436

4-3-6 REAR HEATED OXYGEN SENSOR, COMPENSATION





Trouble Code Conditions
- The rear heated oxygen sensor (HO2S) constantly monitors the front heated oxygen sensor, ensuring that it adjusts the short term fuel trim integrator so that it corresponds to the exhaust gas oxygen content. If the short term fuel trim integrator deviates, the rear heated oxygen sensor will make fine adjustments to it. Diagnostic trouble code (DTC) EFI-436 is stored when this adjustment is too great and the engine control module (ECM) interprets this as a damaged front heated oxygen sensor.

Substitute value(s)
- Twin heated oxygen sensor fuel trim disabled.

Possible source(s)
- Uneven compression.
- Air leakage in the intake system.
- Air leakage in the exhaust system.
- Defective rear heated oxygen sensor.
- Defective front heated oxygen sensor.

Fault symptom(s)
- May result in poor performance.