Mercedes Diagnostic errors

Ref: VIN WDBJF82J1YX037227 2000 E320 4-Matic sedan

Diagnosis errors.

The problem surfaced as a starting failure, the engine would refuse to start. It would crank but not catch until the second or third try. This problem occurred about once in ten starts. (1 in 10).

El Dorado Hills Mercedes diagnosed the problem as a faulty crank position sensor. The reason for the failure was given as a leaking rear crankshaft seal. The car had never shown any signs of leaks, no spots in the white concrete driveway, no loss of oil on the dipstick. The device had not been kept or tested to make sure it was the problem. As a Hall effect device I was surprised that it was so sensitive to oil.

The crank position sensor was replaced and the rear crankshaft seal replaced.

Returning from the repair on a twisting two-lane road (hwy 49 at the Calaveras line heading South). The ?check engine? light flashed two times and stayed on. The car immediately went into ?limp home? mode and did not have the power to climb the hill. My wife was able to pull off the road but waited for an hour for a wrecker while lumber trucks roared by feet away. No fun. The car was brought to our home in San Andreas. The car was taken to El Dorado Hills Mercedes the next day.

The diagnosis this time was a faulty catalytic converter. The first thing that occurred to me was that Mercedes would never throw a car into ?limp home? for a catalytic converter. It?s far too dangerous. I suspected an incorrectly installed or defective crank position sensor. But no, I was assured that the catalytic converter was defective and it rattled. The catalytic converter on every one of my old Mercedes rattled if you banged on it.

The catalytic converter was replaced.

We picked up the car and my wife drove it around the Gold Country for a week, mostly short trips. The original symptom returned twice. My wife was driving home from Senora on Hwy 49 when the same thing happened. The ?check engine? came on and the car went into ?limp home? mode. Once again, not enough power for the hills. Sally was able to get off the road and was stranded on the side of the road for an hour (again) waiting for a tow truck.

When we got the car home I ran scan on the trouble codes in the car at that time. I used a UFI tech diagnostic code reader.

The codes were: 300, 301 and 306, these would indicate misfiring on both banks.

The last code was interesting; it was 1603 CAN of EIS. The CAN is a type of local areas network that the car uses to communicate with its components. The EIS is the Electronic Ignition System. In other words the network that the key start uses has a problem.

We started with key a start problem, and we still have one. The crank position sensor may have been oily but it had nothing to do with the problem. The catalytic converter was a shot in the dark from a diagnostic standpoint. I would believe it if a tailpipe analysis had been done before and after the replacement of the catalytic converter.

The dealer just called and now the diagnosis is ?bad spark-plug wires? E320 doesn?t have spark-plug wires so I assume they are referring to the coil units on top of each spark plug. He said he changed two and the car still goes into ?limp home mode? after a short while. It seems to me that he is mistaking a symptom for a cause. Something is causing the ?limp home mode, he still seems to be shooting in the dark. You know what they say. ?When you?re shooting in the dark you have to use a lot of bullets??

Harry Graham

Is it a manual or an automatic?

My gf recently had an issue with her Mercedes powered car, where they had to replace the flywheel with a new one, during a clutch job.

When the new flywheel was installed, the car would go into limp mode if the car was driven under load (merging on the highway, climbing a hill, etc).

Brought it back to the dealer, where they diagnosed the cause as being one of the fingers on the tone ring, which triggers the crankshaft position sensor, was slightly damaged (they say from the factory). During running, this tone ring finger came into contact with the CPS, and damaged it too, so both had to be replaced.

Once both were replaced, the car was back to normal.