Diagnostic Trouble Code (DTC) Information

Diagnostic trouble code (DTC) information EFI-212

EFI-212 Front heated oxygen sensor (HO2S), signal

Condition




Before fuel trim starts the front heated oxygen sensor (HO2S) must be ready - it should be at operational temperature and have the correct output voltage. Monitoring of the heated oxygen sensor (HO2S) function starts approximately 3 minutes after heated oxygen sensor (HO2S) heating starts. Diagnostic trouble code (DTC) EFI-212 is stored if there is a fault in the front or rear heated oxygen sensors (HO2S) or their cabling that affects the output voltage from the front heated oxygen sensor (HO2S).

Substitute value
- fuel trim disabled
- three-way catalytic converter (TWC) diagnostic disabled.

Possible source

Signal too high:
- short-circuit to supply voltage in front heated oxygen sensor (HO2S) signal cable (+)
- short-circuit to supply voltage in front heated oxygen sensor (HO2S) signal cable (-)
- short-circuit to supply voltage in rear heated oxygen sensor (HO2S) signal cable (+)
- short-circuit to supply voltage in rear heated oxygen sensor (HO2S) signal cable (-)
- defective front heated oxygen sensor (HO2S)
- defective rear heated oxygen sensor (HO2S).

Signal too low:
- short-circuit to ground in front heated oxygen sensor (HO2S) signal cable (+)
- short-circuit to ground in front heated oxygen sensor (HO2S) signal cable (-)
- short-circuit to ground in rear heated oxygen sensor (HO2S) signal cable (+)
- short-circuit to ground in rear heated oxygen sensor (HO2S) signal cable (-)
- defective front heated oxygen sensor (HO2S)
- defective rear heated oxygen sensor (HO2S).

Signal missing:
- open-circuit in signal cable (+)
- open-circuit in signal cable (-)
- defective front heated oxygen sensor (HO2S).

Faulty signal:
- short-circuit between signal cable (+) and signal cable (-)
- defective front heated oxygen sensor (HO2S).

Fault symptom[s]
- none.