Diagnostic Trouble Code (DTC) Information

Diagnostic trouble code (DTC) information

Condition
The rear heated oxygen sensor (HO2S) signal is checked when the control module carries out a three-way catalytic converter (TWC) diagnostic. A diagnostic trouble code (DTC) is stored if the rear heated oxygen sensor (HO2S) signal is not within the range permissible for three-way catalytic converter (TWC) diagnostics. Diagnostic trouble code (DTC) ECM-1A is stored if the signal from the rear heated oxygen sensor (HO2S) is too high, too low or missing.

Substitute value
- Fuel trim disabled
- Three-way catalytic converter (TWC) diagnostic disabled.

Possible source

Signal too high:
- Contact resistance in the terminals
- Short-circuit to supply voltage in the signal cable
- Defective rear heated oxygen sensor (HO2S).

Signal too low:
- Contact resistance in the terminals
- Short-circuit to ground in signal cable
- Air leakage in the intake system
- Defective rear heated oxygen sensor (HO2S).

Signal missing:
- Contact resistance in the terminals
- Open-circuit in the signal cable
- Defective rear heated oxygen sensor (HO2S).

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