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Old 03-16-2005, 02:41 PM
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Join Date: Jan 2004
Location: San Antonio, Texas
Posts: 46
Check Engine light, 300E 1990

The last couple of days My check engine light has been comming on after I remove the key from the ignition. Last night it was on all night and ran the battery down. After I start the car it goes out. The only thing I have done to the car in the last week is replace the fuel pumps. They shouldnot be powered with the key off. Any ideas?

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Old 03-16-2005, 06:42 PM
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Join Date: Feb 2005
Location: Columbia, MD
Posts: 82
This is odd with the light on when the switch is off and key removed.
When I have done work that causes a regular "check eng." lite I just "erase" the codes by doing the following which I got from a mechanic: disconnect the negative lead on the battery, turn the ignition switch on all the way (not start), step on the brake pedal, and reconnect the ground cable. I have never had the light stay on or come back on so I assume that as long as the trouble is fixed the light will stay off. I don't know if this will help in your case.
It sounds like you may have a short or a cross some where if "erasing" doesn't help.

Last edited by carymcooper; 03-16-2005 at 06:45 PM. Reason: yes
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Old 03-17-2005, 07:17 AM
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Join Date: Jan 2004
Location: San Antonio, Texas
Posts: 46
I found the problem. When I was checking the engine compartment for a short, I touched the OVP and felt that it was too warm, hot even. Even though I had replaced the OVP a while back when I was trouble shooting another problem. I pulled the OVP and found that it was full of water and corroded badly. Luckily, I had not thrown the old OVP away. I reinstalled it and the light went out and all works well. Side benefit is that the car now starts on the first rev. This is a inherent problem with this model as I have seen in it other posts. Water seems to drain directly on the top of the OVP. I suggest covering it with some tape or plastic to keep it dry.

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