Thanks to someone here, I got a recommendation for a Bosch Fuel Injection manual. I got a copy and it is very good.

In the manual it shows how to retrieve fault codes by using a spare fuse in the fuel pump relay for the KE3 Jetronic. I cannot find the fuel pump relay, or the MB application does not provide this in the fuel pump relay. The book indicates that by using the fuse and following the procedure, the check engine light will flash the stored codes.

Does anyone know where to do this? I would expect that this can be done if you know where to do it. I hate to be forced to go to the dealer to retrieve the codes with their diagnostic link. I have been retrieving codes using nothing more than a paperclip on my POS Vette for quite some time, I would like to know the secret on this one.

Thanks for any help you can offer,

Larry,

The fuelpump relay is behind the battery behind a black plastic cover. You have the computer there, to the right of it (if you face the car) there are three relays, one is the overvoltage protection relay with the fuse on top of it (it is smaller then the other two) , the other says "Klima" on it and the third one is the fuelpump realy. It is black in colour same size as the "Klima" one. It is a sealed unit. According to my Electrical Trouble Shooting manual there is a Diagnostic Socket on the left front inner fender, it is blak with a round srew-on cap on top of it. By the way this manual is available from the dealer in paperback for a nominal fee (around $15.00).

Alex

Alex,

Thanks, this gets me further along. I have found the diagnostic connector. But, what I really need to know is how to retrieve a code. Does the electrical troubleshooting manual tell you how to retrieve the codes? In the Bosch fuel injection manual it says there is a connector on the fuel pump relay which will accept a fuse to retrieve codes, and gives the procedure for doing so.

I will look at the fuel pump relay to see if it has the connector as Bosch says it should.

Does anyone know how to retrieve the codes without the diagnostic equipment?

Thanks again and have a great day,

------------------
Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

My Bosch manual indicates that you can retrieve the fault codes by reading the Check Engine light flashes. I have the code chart. The procedure involves the spare fuse socket on the KE 3 Jettronic, but this obviously is not accessible on the '88 300E. Does anyone know how to trigger the check engine light flash code retrieval on this application?

Thanks for the help,

------------------
Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

On CIS cars only California cars have code info! Use a standard DDM with duty cycle to read Lamda on Fed versions.

I know that the Cal. versions have the button for this, but the controller should have the codes stored, if one just knew how to get them out.

Thanks for any help from anyone,

------------------
Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

Larry,

I have checked the Electrical T.S.M. but there is no mention in there for trouble codes. However here is what I found in the Service Manual Engine 103,under the heading : "Testing electrical components of CIS-E injection system.

Basic and national versions.

A. Without trouble diagnosis by means of on-off ratio

Up to March 1986 no fault detection is integrated in CIS-E control unit.

B. With trouble diagnosis by means of on-off ratio

Starting March 1986, faulty input signals are detected by CIS-E control unit and transmitted to lambda measuring output (the round six-pole connector on the left front fender). Faults are picked up by means of lambda control tester at diagnosis socket.

Fault detection permits testing different components of CIS-E injection system by means of measuring the on-off ratio.
Fault detection of control units:

On-off ratio indication Control unit
_____________________________________________

70% with fault detection
100% without fault detection "
Sorry but it seems you are out of luck here (unless of course you have one of those lambda meters :-).
Perhaps you can post the problem here and someone maybe able to help you out.
Regards

Alex

dacia,

Thanks very much for the response. I have a DVM with duty cycle function. As I have understood, the duty cycle indicates the fuel/air ratio.

Additionally, mine is an '88 model. Bosch provides fault code error trapping within the controller for the KE3 Jettronic. I can't imagine them removing the fault code trapping for MB's use of the unit. There must be a way to retrieve these codes. I'm sure that the dealer has some way even if it is their expensive diagnostic system. Most every car with fault code trapping has a means of retrieving the codes without the use of the expensive system owned by the dealer. Thanks again for the response.

Have a great day,

------------------
Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles

Yes the on/off ratio tester is the FAULT tester as well. If the volt meter moves there aren't any faults. If it stays at 10%, 20%, 30%, and so on then there is a fault. This is the ONLY fault system on federal version cars.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
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Retired Moderator

Okay, from this is there a way to decode a fault from the % Duty Cycle reading? Is there a code of some kind. Where can I find the key to tell which reading means what? Is there a way to get a 4 digit code from this?

Thanks,
Larry

As far as I know, fault codes are only stored if the check engine light is on or comes on from time to time. If your light hasn't come on, I'd be surprised if you get anything more than an 'all clear.'

Sixto
78 450SEL
91 300SE

Hi Larry,
There seems to be some confusion. It sounds like you have a book that covers VW/Audi stuff. I seem to recall a method that used the fuse connection in the fuel pump relay and had 4-digit codes....but I've tried real hard (with some success) to forget it.
Though the fuel systems are similar and made by the same manufacturer, they share little in terms of diagnostics.
The "fault code" system used by Mercedes is very different. If you had an 89 model, it would be easy to get and check/erase codes. Early version Mercedes fault detection was done through the on-off ratio tester. I never had much luck using it myself since most of the faults were just as easy to find with a DMM. You need the MB manuals to fully explain the process.
Regards,
Randy D.