DTC EFI-435

4-3-5 FRONT HEATED OXYGEN SENSOR TO SLOW





Trouble Code Conditions
- The engine control module (ECM) continuously monitors the time (period 3.3 seconds) it takes for the HO2S to switch from rich to lean and back to rich again. If this time is too long, the engine control module interprets this as a fault in the front heated oxygen sensor (HO2S) and diagnostic trouble code (DTC) EFI-435 is stored.

Substitute value(s)
- Twin heated oxygen sensor fuel trim disabled.
- Pulsed secondary air injection (PAIR) diagnostic disabled.

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

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