550 Check Engine Light

A 2000 550 that I am considering buying has an intermittant check engine light. It has 11k miles, well serviced and otherwise in great shape. My PPI mechanic sez all four oxygen sensors need to be replaced. Presumably, the OBDII diagnosis should show a corresponding code. Any experience or advice here?

Thanks.

MMB

 

Before replacing them, I'd try removing and cleaning the O2 sensors (CRC, brake cleaner, general solvent, etc.) These are temperature/resistor devices and when there is a build up of post-combustion crud on them then it can alter the readings, so cleaning might work. Then again, it is no guarantee that this will solve it but for a little effort you could save a lot of bucks. It used to work in my Bosch L-Jetronic FI unit every few years.

 

It's the seller's nickel, so I'll have them all replaced. I just want to make sure that it isn't something more complex and expensive like the ECUs.

Thanks.

 

If replaced, ask for the removed units back and examine them.
I'll bet they are dirty and could be cleaned for use in the future

 

I had error codes for the two driver side O2 sensors, scanned and cleared them with Innova 3130 tool (cheaper models should also do the job). Make sure your 550 has the extra earth pin job already done by the dealer (see earlier threads) for the OBDII connector.
Cleaning the sensor contacts sounds like good advice, in my case 7000m car, it was not necessary.
Regards,
Ron

 

Thanks. I'll keep you advised.