Well, I just got a hell of a shock. We sent our '98 ML320 into the shop (indie) for a service which should have been plugs, belts, hoses, and fluid change for $500 and came out with a $1600 bill. Part of this was to change all four O2 sensors and do the frount brakes.

Now the frount brakes and upgrading the fuel filter I can understand but the O2 sensors throw me for a loop.

A couple of month ago, I went in with a CEL and it was diagonised as a bad MAF....OK that makes sense....and it was changed. Since then, I have not had a CEL but when I took it in this time, the mechanic said that when they did the CEL, it also indicated that the O2 sensors were bad but they didn't replace them at that time. (don't know why).

My question is: If the O2 sensors were really bad, shouldn't I have had a CEL even after the MAF was replaced? Is there a way I can verify the sensor condition when they are off the car.

tks for any input.

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Litton
'90 420 SEL (sold)
'72 280 SEL 4.5
'98 ML320 (for sale)
'86 560SL
'05 Jeep Grand Cherokee Ltd (offroad in style)
'87 Chevy Blazer (AZ Pin Strips)