Diagnostic trouble code (DTC) information

Condition 

The control module continuously checks three-way catalytic converter (TWC) efficiency by comparing signals from the rear heated oxygen sensor (HO2S) with the front heated oxygen sensor (HO2S). Diagnostic trouble code (DTC) ECM-4801 will be stored if the efficiency of the three-way catalytic converter (TWC) deviates too much.

Substitute Value 

Rear heated oxygen sensor (HO2S) control 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.