Oxygen sensor heater circuit malfunction


P0135 - upstream of catalyst (front) / rear (RH) bank


P0147 - downstream of catalyst (rear)

P0155 - upstream of catalyst (front) / front (LH) bank

P0161 - downstream of catalyst (rear) / front (LH) bank


Emissions Equipment Information

Three o2 sensor system (KL engine with one catalytic converter) - A front sensor is positioned on the LH bank and a middle sensor is positioned on the RH bank upstream of the catalyst for closed loop fuel control.  A rear sensor is mounted downstream of the catalyst to monitor its efficiency.

Four o2 sensor system (KJ / KL engine with three catalytic converters) - Front sensors are mounted upstream of the RH and LH warm-up three-way catalyst (WU-TWC) for closed loop fuel control.  Rear sensors are mounted downstream of the WU-TWCs to monitor their efficiency.


Detection Conditions

Diagnostic Support Notes

Possible Causes


[P0135 / P0141 / P0147 / P0155 / P0161 - From 1998 and 2002 Mazda Millenia factory service manuals]