It could be the sensor, its wiring or the engine computer tht is causing the problem. You had wasted a lot of time and money on something that did not solve the problem. Were the wirings checked for shorting or open circuit?
Was the replaced O2 sensor OEM?
This trouble code would make the ECM go into fail-safe mode meaning the fuel would not be metered according to operating conditions but on a fixed programmed delivery and this would result in increased fuel consumption.

Answered by KHLow2008 (expert)
39,806 answers provided

Another thing that was also checked was the plug and the tail end exhaust: it seems to be that the tail end exhaust doesnt give out carbon shoot and when the plugs where checked, it seems ok. As in, it seems to fire properly. What else would u recommend sir?

Response from danielogbonnaya
1 question asked

Also the voltage to the O2 sensor was checked and confirm to be within spec: 5volts, but what ????am n????o?????t??? sure about is weather the replaced O2 sensor is OEM: how can this be checked ?

Response from danielogbonnaya
1 question asked

The code is for a heater circuit, voltage should be 12 volts.
OEM would come complete connectors and would be rather expensive.

Answered by KHLow2008 (expert)
39,806 answers provided