Dashboard Light and Fuel Fault Codes - 850SE 2.5 1994

[Steve_T]

Hi all,

I have a dashboard light which stays on continuously, its the green triangle described as 'Fault in the Engine Electronic System' in the manual.

I checked the fault codes and I have:

5-2-1 - 'Oxygen Sensor Pre-heating - Front' (what does 'front' mean?)
2-1-2 - 'Oxygen Sensor'

I guess unless the wires to the oxygen sensor are bad I have to replace the sensor. Is there any test I can do to check the sensor is bad like put link or some dummy load on the O2 sensor wires to simulate a good sensor?

Thanks for any input.
Steve

[matthew1]

Front means the front O2 sensor. There are 2.

I had a 2-1-2 and it didn't go away. I replaced the sensor (front) and the code went away, and my fuel economy went up

It's an easy job if you buy an OEM Volvo sensor. The job gets harder if you get a Bosch universal O2 sensor, but you save money. I traded advertising on this site for an OEM, and it was cake. The hardest part was getting the damn wires attached via the impossible-to-reach harness in the deep back/low right side engine bay (as you stand looking at the front of the car).

Hit the old sensor with some loosening agent 30 min before starting. It gets rusty down there.

[Steve_T]

Thanks for the feedback Mathew