Diagnostic trouble code (DTC) information ECM-401C

Condition 

The engine control module (ECM) continuously checks three-way catalytic converter (TWC) efficiency (bank 2) by comparing signals from the rear heated oxygen sensor (HO2S) with the signal from the front heated oxygen sensor (HO2S). The diagnostic trouble code (DTC) is stored if the efficiency of the three-way catalytic converter (TWC) deviates too much.

The diagnostic trouble code (DTC) is diagnosed when driving under specific driving conditions.

Substitute Value 

The rear long-term fuel trim is disabled.

Possible Source 

• Misfiring
• Leakage in the intake system
• Leakage in the exhaust system
• Faulty fuel pressure
• Uneven compression
• Damaged catalytic converter.

Fault symptom[s] 

• Malfunction indicator lamp (MIL) lit.