DTC ECM-4201

Condition
The engine control module (ECM) controls the three-way catalytic converter (TWC) application (after start up) by changing between rich and lean fuel mixture. When the change takes place the signal from the rear heated oxygen sensor (HO2S) and the speed of change are checked.

Diagnostic trouble code (DTC) ECM-4201 is stored if the engine control module (ECM) registers that the rear heated oxygen sensor (HO2S) changes too quickly.

Substitute value
None.

Possible source
- air leakage in the exhaust system
- defective three-way catalytic converter (TWC).

Fault symptom[s]
None.