Emmision failed-ghost CEL - PeachParts Mercedes-Benz Forum

alenko123 · #1 11-30-2007, 03:54 AM

A week ago I replaced brake light switch on 1996 E320 when I had ABS/ETS yellow warning light and no CEL( It fixed the problem,the lights went right off). Two weeks before that I had replaced O2 sensors since I had CEL for bad O2 sensor.Cleared the CEL,drove the car for two weeks, all monitors were OK but Catalyst monitor-still shows not ready.
Finally took the car to the dealer for emmision test hoping they would know some trick to make it ready(cat.monitor) since I thought two weeks was plenty of time driving to make all monitors ready.(it turns out they do not know any more than any other experienced mechanic).However it turns out that this was not an issue and the car would have passed emmision even with cat.monitor not ready if it was not for 'ghost' CEL that only came during inspection saying bad brake switch that I had had replaced and was functioning properly.No CEL when I took the car back nor ever since I cleared CEL after replacing O2 sensors. I pluged my code reader and no current CEL nor any pending fault codes.
I talked with a senior mechanic(at the same MB dealer shop) and he has never seen that before and that CEL has nothing to do with ABS/ETS and that those are operated with two different modules.
I do not know if I am supposed to junk $7000 worth car just because some fancy equipment would not let me pass emmision for something that is in good condition(or new in this case) and even not emmision related?
Has anybody have the same problem or knows what in the heck is going on?
People relly too much on computers in general and I do not think it is a good thing.

mbdoc · #2 11-30-2007, 08:10 AM

ON that model & almost all MB's after 1993 with electronic throttle actuators, the control of the throttle is done by the fuel computer OR on some MB's by the EA/CC/ISC computer. EITHER way that is part of ODB2 monitoring.

They need to find out WHY the EA computer keeps spitting out that problem & why the DM (diagnostic Module) keeps picking up that problem.

david s poole · #3 11-30-2007, 09:45 AM

here in tx you are allowed to have at least two monitors "not ready".i would assume that if the cat is not ready that the before and after o2 sensors are not showing the ecu an attained level of efficiency.maybe if you warm up car and use a scanner to read the before and after sensors you may get an insight into the cause.maybe something simple like the o2 heater in the rear sensor not operating.[blown fuse or bad connection]