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Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53151
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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I have a 1991 560sel and the check engine light comes on,

Customer Question

I have a 1991 560sel and the check engine light comes on, engine revs, light goes out, engine idles. What causes this?
Submitted: 1 year ago.
Category: Mercedes
Expert:  Marty replied 1 year ago.

Hi, my name is***** bad overvoltage protection relay is the usual cause of this problem. I'd try a new relay and see if it solves the problem.

Let me know if you have any questions.

Please click on a rating for my service.


Customer: replied 1 year ago.
I'm going to get a new relay and see if that takes care of the problem. I'll let you know.
Expert:  Marty replied 1 year ago.

Thank you for getting back to me. I'll wait to hear from you.


Customer: replied 12 months ago.
Replaced the relay; didn't correct the issue. Check engine light comes on, smog pump clutch engages, engine revs then almost dies, check engine light goes out, engine idles normal.
Expert:  Marty replied 12 months ago.

How often does this happen?

Customer: replied 12 months ago.
Happens whenever I start the car now. After about 10-20 seconds it does the same thing. Since it's obviously not the K1 relay what's your next best guess?