Question about 1991 Mercedes-Benz Mercedes Benz 500 Class

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ECU I own a 500SE '91 W126. How do i reset the ECU?

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ECU doesnt get reset its fixed. If your trying to clear a CEL you need a reader. You can make one by going to benzworld.org and looking up homemade reader. The reader can clear codes also.

Posted on Jul 09, 2009

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Audi 500se


Most all electric fuel pumps are ok as they shut off when the needle and seat closes when the curb is full. choose one with a mounting to suit.

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1989 Mercedes 560 sel, w126, Car will start and idle fine for 10 min. then stall and will not restart until next morning...


catalytic converter is clogged basically its stopping up your exhaust. Over time the pressure will slowly vent out, allowing your car to start, only to build up the backpressure again, stalling engine.

Dec 10, 2013 | Cars & Trucks

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Ecu located


90-91, its under the dash, on the left side of the steering wheel. The ECU is the one farther towards the door. Just a side note if you need it, abs controller is under the passenger seat.

Dec 06, 2013 | 1990 Subaru Legacy

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Cant find the fuel injection relay on 91 Geo storm


the 91 cars , typically have 3 fuses that must be good.
to get fueling.
why do you need to find a non existent relay.?
state the symptoms, and stop guessing.

3 fuses that make the ECU operate
then the ECU drives the inector, directly.

the full schematic is in the FSM and here
alldata dot com.
or in most public libraries, in the e-sources , directory, click Autorepair (free too)

my comment is to a USA person, unstated. that.

Sep 27, 2013 | 1991 Geo Storm

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I have a 91 talon tsi awd. the kid i got it off did some stupid thing with the stock wiring harness. now the car has a problem starting but after start up the car is a beast. i feel like the car isn't...


Since this is 91, its likely that the original engine has been replaced, and various other mods have been done. Essentially you need ot figure out what the previous owner did, and either fix it or ignore it.

A common "trick" with the wiring is to change the MAF sensor (on the air filter can) around to get more fuel at high boost. Pull off the 8 pin connector and check for bent pins. Check for 5V (NOT +12v) on one of the pins, as this is the MAF sensor supply voltage.

Other issues are the coolant temp sensor (2 pin sensor with black? connector on the themostat housing) connection.

If the temp sensor is not properly connected, or the wrong sensor for the engine, it will be hard to start esspecially when cold.

If possible, verify what ECU is fitted. The 90-91 ECU has slightly different pin connections to the 92-94.

You may also have fuel pump relay issues. This is the large can in the center console, near the ECU.
Open the ECU and check the large electrolytic capacitors for leaks. Its a common problem, and there various people around who will replace them before they destroy the ECU board.


Check all the vacuum hoses for cracks and leaks. Check the hoses for the intercooler and up to the throttle body.

Have a look at www.lancerproject.ca for more information.

Dec 22, 2010 | 1991 Eagle Talon

2 Answers

Fuel pump


Check under you back seat... remove the cover, remove the fuel pump and install the new one, then install de cover again, and then the back seat.

Jul 18, 2009 | 1991 Honda Accord

2 Answers

Need to reset the ecu on a 91 nissan sentra


unhook negative battery cable for 5 second and this will clear all codes

Feb 04, 2009 | 1991 Nissan Sentra 2 Door

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