My 99 CLK430 has 58k miles on it. The basic warranty is expired but it's still under the emmissions warranty. Has anyone had their oxygen sensors replaced under the emmissions warranty?

I am pretty sure that the O2 sensors are causing my check engine light to go on intermittently (it's on about 60-70 percent of the time). I am not 100% sure because they started lighting up after I changed the air filters. I hope the air flow meter wasn't damaged when I had to tap on the air filter housing while reinstalling (if anyone has done this themselves, you know what I talking about...the housing is compression fitted onto the intake).

Is there a way to read fault readings easily besides taking the car to the dealer? When I used to have an M3, I could perform a series of gas pedal pushes and the dash would indicate any fault codes via a series of light flashes. Anyway to do this on a CLK? Is there an affordable diagnostic tool available?

TIA

Well, apparently the oxygen sensors are NOT covered under emissions warranty. Total BS since they are probably one of the most critical components of the emissions system.

Lesson learned: make sure you get those O2 sensors replaced right away if your check engine light ever comes on (before 50k miles).

with the myriad trouble codes that can make the 'check engine' lamp come on a scanner is the best tool as a starting point.

The OBD-II scanners run about $350 - $400 and unless you are going to do all your own repairs, it might not cost out.

Plus, the trouble code doesn't simply mean change the part - you have to use troubleshooting flowcharts to eliminate electrical harness issues, vacuum leaks, or sensor failures. The trouble code is a diagnostic aid, but not an exact indicator of a bad part...it will narrow down the systems to look for problems with.

Just replacing parts in an elimination type of basis might solve the symptom or be a very costly guessing game.

There are MAF, TPS, ESC, EVAP, BARO, O2, etc. types of sensors all over various parts of the car, engine and exhaust systems. Not to mention some of the anciallary systems tied to the ECM.

I had my car in the shop a year ago and had 3 check engine light events - the shop didn't diagnose completely and found that I had a faulty ECM - replaced under warranty. This was after replacing two EVAP cannister valves and a gas cap that weren't the source of the problem.

for all those who have had O2 sensor problems, what year is your CLK?

Hal: you're right, it could have been a number of other things but the car symptoms just made me guess (correctly) that an O2 sensor was at fault. I am just in disbelief that it is not covered under the emissions warranty when it is clearly a critical component of the system. I've owned 7 other german cars (BMW, Audi, Porsche), none of which ever had an O2 sensor problem.

By the way, the dealer also fixed a BAS/ABS/ESP light issue by tightening a loose connector. I don't know which connector it is yet.

mmgrad: My car is a '99.

there are varying lengths of time/milage for emissions related components

plus California has some variances on the Federal emissions warranties - some items are 7yrs/70,000 miles and other things are 5yrs/50,000miles and so forth.

I've never had an O2 sensor go bad, and on OBD-II cars (model years 96 +) there are pre-catalyst sensors and post-cat sensors.

With the MB V6 or V8 engines you'll have 4 O2 sensors, so it could get expensive - and I would certainly look into if the warranty covers it.

Another resource is the C.A.R.B. - they've got websites that will go into this stuff as well...