The first time the engine light came on I took the car to my mechanic. He diagnosed the problem to be one of the O2 sensors. I had him replace both O2 sensors for maintenance reasons. The light was off afterwards. I then had some stalling problems and was recomended in this forum to replace the original OVP relay for the new replacement one. I ordered it from the Partshop and replaced it myself. When I replaced it I was under the impression that the engine light would come on then and you would have to unhook the battery for an hour to reboot the computer. The light did not come on after I replaced the relay and only after about 20 miles or so did it light up again. I then disconnected the battery to reboot the computer, thinking that it was taking several miles for the computer to recognize the new OVP relay. The light stayed off for about 70 miles or so and now it is on again. What could possibly be the problem now? Any help would be appreciated. The car has 60,000 miles. Thanks.

The check engine light on this car will come on for more than 60 reasons. There are several codes that could be the cause...You need to take and have the codes read to start the repair process.

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Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS

I found the problem. When I went to show my mechanic where the OVP relay was. He spotted a small vacuam hose that was disconnected near the OVP. I must have accidently disconnected it when I was replacing the OVP. The light turned off after connecting the hose.

So how do I check the codes?

My jeep has a procedure where you turn the ignition on and off 3 times in a row, and the "check engine" light flashes the code.
Is there anything like this on the Mercedes? or do i need some kind of reader?

TIA

All US C-Class & all other 1996 & later cars have "ODB2" diagnosis for the fuel system, you need a scan tool to read codes!

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MERCEDES Benz Master Guild Technician (6 TIMES)
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Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

According to this thread...

CLK 430 Problem

It's possible to read fuel system codes from the climate control.

Kuan

The replies I made in that thread (I didn't reread all the replies) only apply to the A/C system.

The A/C system has the ability to give fault codes only for its needs (some of them are engine related). It also has the ability to give many "actual values" which do apply to the motor such as engine speed, engine temp, vehicle speed, etc. While these can be interesting and even usefull they will not give codes on engine management, HFM in this case. It also will not give codes on the DM (diagnostic module which turns on the light) or the EA/CC/ISC (electronic accelerator/cruise control/idle speed control - this car might have it in the HFM controller) which can cause the light.

These modules were sorted out when the system was changed to ME in about 1997. The ME consolidated all fuctions into one module...one set of codes...FOR ENGINE. The new models have many systems with controllers that have self diagnostics. There are these basic groups: Engine, Body, Chassis, Climate control. Some cars have 10 or more controllers in the body section.

Checking codes in OBDII cars is available rather cheap (with various scanners/software) because of the government mandated standardization. This does not apply to the 10 to 30 or more controllers running the rest of the car.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician