300SE High Idle Problem/Check Engine Light
02-20-2006, 07:22 PM
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300SE High Idle Problem/Check Engine Light
My 1991 300SE has the check engine light on and is having an idle problem. I'm totally new to MB vehicles but I am pretty technically competent (extensive experience with turbo 4 cylinders and carburated V-8s). I'm assuming the light and the idle problem correlate as they pretty much both started happening at the same time. The idle in P goes up around 2k RPM, especially when it's hot. Does anybody have any experience with this problem and also how to read the codes out of the ECU? Thanks!
02-21-2006, 04:11 PM
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1991 560SEC Teal 1989 420SEL Ice Blue 1984 500SEC White
Idle Problem/Check Engine Light
There is an overload voltage regulator. It is most likey on the firewall on the other side of the break booster. It has a red fuse in the top. Try replacing the fuse first, if that is not it you might have some soder joint cracks in the OVR unit.
Bruce
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Bruce
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02-21-2006, 06:51 PM
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The fuse appeared to be intact, however, I replaced it anyway. This did not solve the problem. I've read on some other threads about the idle control valve and similar issues. Also, how would I read the codes out of the ECU?
02-24-2006, 02:27 AM
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Just to clarify to make sure I get the right part, this is seperate from the regular voltage regulator? Also, out of curiosity, what exactly does the overload voltage regulator do?
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02-24-2006, 08:46 PM
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Ok...I got the new overload relay from my local MB dealer and swapped it. I also disconnected the battery for about 20 mins to reset the ECU. The check engine light came back on after the car was running for about 1-2 minutes. The idle is significantly lower now but still high (idles around 1300-1400). Before I start replaced other sensors (like the idle control vavle) I would like to pull the codes out of the ECU. Where would I connect the leads for the LED and is there a website out there that has a list of the different codes?
