DTC ECM-4901

Diagnostic Trouble Code (DTC) Information





Condition
The control module continuously checks threeway catalytic converter (TWC) effectiveness by comparing signals from the rear heated oxygen sensor (HO2S) with the front heated oxygen sensor (HO2S). Diagnostic trouble code (DTC) ECM-4901 is stored if three-way catalytic converter (TWC) efficiency deviates too much.

Substitute value
- Rear heated oxygen sensor (HO2S) is disabled.

Possible source
- misfiring
- air leakage in the intake system
- air leakage in the exhaust system
- faulty fuel pressure?
- uneven compression?
- defective three-way catalytic converter (TWC)

Fault symptom[s]
- malfunction indicator lamp (MIL) lit