Troubleshooting Hints

The most likely causes for this DTC to be set are:

• ECM (M/T) or PCM (A/T) failed.
• Heated oxygen sensor (front) deteriorated.
• Open circuit in heated oxygen sensor (front) output line.
• Open circuit in heated oxygen sensor (front) ground line.
• Heated oxygen sensor (rear) deteriorated.

When the heated oxygen sensor (front) begins to deteriorate, the heated oxygen sensor output voltage will deviate from the voltage when the sensor was new (normally 0.5 volt at stoichiometric ratio). This deviation will be corrected by the heated oxygen sensor (rear). If the heated oxygen sensor (rear) responds poorly because it has deteriorated, it will improperly correct the heated oxygen sensor (front). Thus, even when closed loop control is being effected, the fluctuation of the heated oxygen sensor (front) output voltage decreases, without intersecting with 0.5 volt. As a result, there is a possibility of DTC P0134 becoming registered.