Diagnostic trouble code (DTC) information

Condition 

Probe monitoring begins after probe preheating diagnostics are complete. Diagnostic trouble code (DTC) ECM-280A is stored if there is a fault in the front heated oxygen sensor (HO2S) or its wiring causing the signal to deviate from its permitted range

The control module registers four different types of fault:

1. Signal too high

   The control module compares the front and rear adaptation values. A diagnostic trouble code (DTC) is stored when the values deviate by more than 3%.

   NOTE: The fault may be in the front or rear heated oxygen sensor (HO2S) circuit.
   • the control module registers that the signal from the front probe is above 4.8 V for too long
   • the signal from the front probe does not deviate from λ= 1
   • the signal from the front probe is showing a lean fuel mixture while the signal from the rear probe is showing a rich mixture
   • the signal from the front probe is showing a rich fuel mixture while the signal from the rear probe is showing a lean mixture.
2. Signal too low

   The control module monitors the aging of the probe by checking its dynamics when switching between lean and rich mixtures. The diagnostic trouble code (DTC) is stored if the control module registers that the probe is operating too slowly.

   • the control module registers that the signal from the front probe is above 4.8 V for too long
   • the signal from the front probe does not deviate from λ= 1
   • the signal from the front probe is showing a lean fuel mixture while the signal from the rear probe is showing a rich mixture
   • the signal from the front probe is showing a rich fuel mixture while the signal from the rear probe is showing a lean mixture.
3. Signal missing

   The control module monitors cross-induction from the probe preheating. Diagnostic trouble code (DTC) is stored when cross induction exceeds the permitted value.

   • the control module registers that the signal from the front probe is above 4.8 V for too long
   • the signal from the front probe does not deviate from λ= 1
   • the signal from the front probe is showing a lean fuel mixture while the signal from the rear probe is showing a rich mixture
   • the signal from the front probe is showing a rich fuel mixture while the signal from the rear probe is showing a lean mixture.
4. Faulty signal

   A diagnostic trouble code (DTC) stored when:

   • the control module registers that the signal from the front probe is above 4.8 V for too long
   • the signal from the front probe does not deviate from λ= 1
   • the signal from the front probe is showing a lean fuel mixture while the signal from the rear probe is showing a rich mixture
   • the signal from the front probe is showing a rich fuel mixture while the signal from the rear probe is showing a lean mixture.

Substitute Value 

• The rear heated oxygen sensor (HO2S) control is disabled
• Three-way catalytic converter (TWC) diagnostic is disabled

Possible Source 

Signal too high: 

• air leakage in the exhaust system
• short-circuit to power supply or ground in the signal cable (+) or supply cable for pump current
• defective heated oxygen sensor (HO2S)

Signal too low: 

• the cable for calibration current and the cable for pump current are short-circuited to each other
• open-circuit in signal cable (-)
• open-circuit in cable for calibration current
• defective heated oxygen sensor (HO2S).

Signal missing: 

• signal cable (+) and signal cable (-) short-circuited to each other
• one of the cables for heated oxygen sensor (HO2S) preheating is short-circuited to the probe's other wiring
• defective heated oxygen sensor (HO2S).

Faulty signal: 

• short-circuit to supply voltage or ground in signal cable (+)
• short-circuit to supply voltage or ground in signal cable (-)
• short-circuit to supply voltage or ground in pump current cable
• short-circuit to supply voltage or ground in calibration current cable
• open-circuit in signal cable (+)
• defective heated oxygen sensor (HO2S).

Fault symptom[s] 

• malfunction indicator lamp (MIL) lit.