Check Engine Light

[ShaneR]

Hi Guys, I am in need of some technical help: Yesterday the check engine light came on in my 1993 500E at startup. This has happened before, and often it is something minor. I drove the car about 1 mile and parked it and then washed it by hand. When got home I parked the car and locked it and the check engine light stayed on. I then unlocked it and opened the door and the alarm went off. I turned off the alarm by unlocking the door I then started the car then turned it off, the light stayed on. Locked and unlocked, no alarm. Repeated the start up/turn off and light still stayed on. I ended up disconnecting the battery to get the light to go out and left it disconnected over night. Today I reconnected everything and started the car and the light came back on, but did not stay on after I turned it off. Does anyone have an idea of what would have made the light stay on after the car was turned off? Thanks in advance for any help or tips.​

 

[gsxr]

If the CEL is staying on with the key turned off and removed from the ignition switch... I would suspect a defective DM (Diagnostic Module). That is very strange.

I would also check codes, at least from the DM using the built-in LED in front of the CAN box, and preferably check codes on all modules using a hand-held blinker box.

 

[ShaneR]

Thanks. I am not very handy, but hoping to become more so. Where is the can box located and how do I check it?

 

[gsxr]

The CAN box is under the hood, on the passenger side, near the windshield... it's the big rectangle with a black cover and a round cap at one corner. In front of this is a plastic block, remove the cap and you'll see a button and an LED. You can use this to check codes on the Diagnostic Module only, which is what triggers the CEL on the dash.

More info on codes is at this link, you'll need the PDF files to translate the blink codes, and for info on how to use the button+LED:
http://www.500eboard.com/forums/sho...s-(Diagnostic-Trouble-Codes)-on-the-500E-E500

Photo of the CAN box & built-in blinker in front of it:

 

[ShaneR]

Awesome, thanks!

 

[ShaneR]

The CEL was illuminated with the engine off when I went down to check the CAM box so I disconnected the battery again, then reconnected it about an hour later and the light did not come back on until I started the car. It went out when I turned the car off, I am going to check it again in an hour and see if it is illuminated with the engine off. I checked the CAM box led and it did not blink, it was a solid illumination indicating no faults. Very odd.

 

[gsxr]

The LED in front of the CAN box is normally off. When you press the button, the LED should illuminate while the button is pressed. Hold for 3 seconds, count the blinks. Then hold another 3 seconds, count the next set of blinks, etc.

If the LED is on continuously... this may indicate a failed diagnostic module (located behind the passenger footwell carpet & metal cover plate).

 

[ShaneR]

It was only on when I was pressing the button, I held it down for about 10 seconds and no blinking.

 

[gsxr]

OK, good. But to check for codes, you have to hold it down for 3 seconds only. It should either come back with a single blink (indicating no codes present), or possible no blinks at all (either meaning no codes, or a module problem).

 

[ShaneR]

Ok, I have finally gotten around to solving this mystery. It turns out that is is: 17 Data exchange malfunction between individual control module. Remember, I am not handy, so my next question is what is the solution to this problem? Can I drive the car with this problem? Any comments or advice would be greatly appreciated. Thanks!

 

[gerryvz]

Check your battery connections at the positive and negative terminals in the trunk to make sure they are not corroded. Including the small red wire that is attached to the positive terminal -- this small red wire provides direct power from the battery to the CAN box. Make sure it is snugged to the positive terminal and making good, consistent contact.

Need to check to see that your four computers in the CAN box are seated correctly and not corroded at their terminals. That means you have to use a 5mm Allen key to remove the CAN box cover, and then use a large flat-blade screw driver to wedge out the computers, examine their contacts to make sure nothing is corroded or bent, and then slide the computer back down into place. Perhaps use a rubber mallet or very light blows from a hammer to make sure each module is seated.

At least that way, you know that everything is OK electrically. That's a good starting point and doesn't require much in the way of tools or special expertise.

Cheers,
Gerry

 

[gsxr]

Afterwards, clear code #17, and see if it comes back. If so, you'll need to get a hand-held code reader to check codes on the other 5 powertrain computers. The built-in LED is only designed to provide a very, very rough idea of the problem.

 

[ShaneR]

How do I clear the code?

 

[gerryvz]

How do I clear the code?

There's a whole thread on that here.

Cheers,
Gerry