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.