I have engine light on dash garage says gas sensors want to send for 2 at a cost of £ 400 They have turned light off with their diagnostic machine but it only lasted a week car running well is yr 2000 230 slk are these parts easy to fit ? What is the gas cap or maf I see mentioned in forums .Will any of this affect my mot due soon ? Thanks Anne

 

You may NOT need new O2 sensors!!

What code was showing when the CEL Check Engine Light illuminated??

I suspect that it is the MAF which may be your problem although O2 sensors COULDS be the problem. This site has a lot about MAF problems.

The key is what code was showing. Why did the garage say it needed new O2 sensors. How did they come to this conclusion?

Garages just love to do repairs that aren't required.

Stuart

 

Have just found the receipt from garage when it went in. Says "suspect fault in 2 sensor units...B18 Altitude Pressure sensor and B28 Pressure Sensor"
He said he could not tell which one so would have to replace both.
Engine runs fine with light on.
What do these sensors do and can I buy them cheaply myself and replace them ??
Dave (Annes husband)

 

The sensors you have just listed are NOT the O2 sensors.

One measurea the altitude that thecar is operating at and the supercharge boost pressure.
Both pressure impact the amount of fuel required by the engine.
Sensors do go wrong however I still wonder what the original problem was.
Testing the sensor is straight forward. Pressure = electrical resistancce of the sensor.

When thecar is connected to a diagnostics scanner you get DTC's (FaultCodes) e.g. P0173 which point to various checks that the engine makes and thus point you towards what MIGHT be wrong.

Most common problem with MB of this age is the MAF and this would be supported by a P0173 code.

Stuart.