C240 How to identify bad O2 sensor??

If one is reallllly bad, all ya need ta do iz wait for Santa Clause next year an ask him! He will know!

mcbrue helpingly under the bridge in the trailer down by the river

96 S420

Not sure why you would think this is a bad O2 sensor. Does the car misfire as when the engine is first started (cold)? If so, then it's not an O2 sensor as they don't activate until they warm up (takes a couple of minutes).

Josh

does not misfire when cold

to me that the only thing i can see in common is the O2 sensor giving wrong info. I can't see 3 cyl actually going bad at exactly the same time. That is one reason i

Bob

I seriously doubt it is bad O2 sensors... Yes, 456 is one one side.

OK, which side, driver side or passenger side. Also, if I am wrong, what is right??

Bob

Where are you? What year is it? How many miles are on it?

O2 sensor malfunction would set the specific trouble codes. The range of 02 sensor trouble codes is P0150 - P0167. You are not getting any of those are you? I believe you have other issues to chase down . I would start with the ignition system.

Peter

Thanks for all of the inputs. My codes were all in the P0304 thru 6 range. I live in the SF Bay area. The car has only 17,000 mi. It's hard to believe that ignition parts wear out that quickley. Maybe it is the 5 years and not the mileage. I am due for my yearly service so I guess I'll let them handle it. I am up for bolting on a new sensor but tearing into the ignition system is a bit much.

Bob

Is your car still under warranty? You mention V-6... it should still be under warranty.

Mine is a 2001 which came with a 4 year waranty. This is year 5. I am taking it to a local independent shop.

Bob

Emissions control parts are covered by an 8 year 80,000 mile federally mandated warranty.

thanks

But since you live in Calif, it is 7 yr/ 70K, NOT 8/80.

This is why I asked in the beginning of your thread: How many miles? and Where do you live?

Where do you live?

How does CA get out of the federal warranty?

California has its own warranty specs. Calif covers things that the 8/80 does not. For smog purposes, Calif is in its own world. Before MB built all the cars to meet Calif specs, they built 2 separate spec cars: Fed version had 491 in the option field, Cal had 494. All are now 494. A prime example are the 1985 300D-T and 300SD. 49 state cars used the 1984 617 engine and the 722.3 transmission. Cal cars used a 617 with a redesigned intake with a trap oxidizer on it. The air filter was no longer on top, it is in the pass front corner. The transmission is the small 722.4.

The 8/80,000 still applies to CA cars.

does not. For smog

Calif specs, they built 2

All are now 494.

617 engine and the 722.3

oxidizer on it. The air

transmission is the small 722.4.

NO NO NO it does NOT. I work at a Calif MB-only dealership and I can tell you 100% that 8/80 does NOT cover Calif version cars.

7/70 is TOTALLY separate from 8/80.

Hey, I don't write the regs. And you don't understand them.

does NOT cover Calif version

There is a fine line between reality and fantasy.....

Reality is, Calif has it's own emission coverage and it is NOT 8/80. Using a model year 2001 gasoline engine as an example: Not counting the 4 yr/50K MB warranty, there are 4 different emission warranties. Federal coverage: 2 yr/24K and 8 yr/80K Calif, Maine, Mass, and Vermont: 3 yr/ 50K and 7 yr/70K If you own a MB, look in your packet for the emissions booklet. It explains all four different emission warranties. Towards the back will be charts of what is covered by what state. As an example, the intake manifold is ONLY covered by 7/70, NOT 8/80. The engine control module is covered by 7/70 and 8/80, The malfunction indicator light is covered by 8/80 but NOT 7/70.

I can take any vin number and submit to MB warranty with a damage code and instantly know if the part is covered or not. I used a 2001 E320 that does not have ELW or Starmark or CPO so the results are not biased. I used 7/70 damage codes and 8/80 damage codes and used 2 different mileage figures, 68999 and

78999. The electric accellerator damage code is 14031737. Under the emission coverage guidelines, it is a 7/70 part ONLY. Using the above car at 68999, it is 100% covered. Using 78999 miles it is NOT covered.

If anyone wants a dose of reality, I can fax you the printouts showing emission coverage in the real world.