[augapfel]

As I delve into the mystery of why the IAC valve on my 91 300CE seems to be dead I thought I'd ask if anyone has a connector face graphic of the K-Jetronic ecu for my car. IAC valve seemingly isn't getting power from the ecu and bothe IAC circuits go straigh to the ecu. Pins 4 and 23 to be exact. Except that I can't positively number the ecu terminals... I THINK I have it right but there isn't a perfect match between the alldata system schematic showing ecu pin numbers and the connector on my car. My confidence level was already low when I selected model year, manufacturer, and model and I was given teh choice of 2.6 or 3.0 engines... Hmmmm. Certainly no mention of 2-valve vs 4-valve engines.

I will begin said web search but if someone knows offhand where such a diagram exists LMK.

 

[Jayare]

Pete

Send a note to LeftCoastGeek. He may have it.or know where to go.

Jim

Sent from my SM-A515U using Tapatalk

 

[michel.s]

Which engine does your car have? m103 or m104. the below figure applies to m103 and m102. As I remember The idle control valves on my M102 have a 12v permanent signal from OVP and the valve is monitored by the Ground signal from ECU Pin No.3

 

[LeftCoastGeek]

a 91 US model 300CE is actually a 300CE-24, with the CIS version of the M104 The wiring diagram should be in the ETM thats in the FSM.... page 48 of this PDF, https://freescruz.com/.priv/W124/w124CD1/Program/ETM/ETM.pdf (labeled page 120/1)

 

[michel.s]

I have the below wiring diagrams for 300CE 1990. the ECU header have 55 connectors. They should apply also on 1991 model. I can notice that pin 5 is direct ground. If you identify that pin on the connector by testing with your multimeter for ground then you ll be able to sort out the pins numbering issue. You may also test for 12volts and this will be pin 1 comming directly from the ovp. This can be used as another reference for more accuracy, (this pin will have 0 volts if you remove your ovp).

On the attached wiring the ICV is powered via pins 4 and 23 as you already mentionned.

 

[augapfel]

Thanks to those who responded. I'll take some time off from work tomorrow morning and try to make some sense of what's going on with my 91 coupe.

 

[augapfel]

Well things just keep getting weirder and weirder.

1) The schematic that Michel.s provides (and is labeled as 1990 300C) is EXACTLY the same schematic that Alldata provides for "regular" M103 powered cars. So that's not gonna work...
2) That schematic seems to apply to vehicle with a 55 pin Jetronic ECU. My coupe has a Jetronic connector with 35 pins. Just for kicks I pulled the Jetronic connector off my 1988 300E with the M103: One row of 12 pins and a second with 13 for a total of 25.
I'll post some pics if I have time.
WTF is going on? This should not be that hard!

 

[augapfel]

Here are pics of the Jetronic ECU from a 1988 300E. 25 pins. Count 'em.

 

[augapfel]

And here's the 1991 CE ECU. I need a beer or 5 to figure this out.

 

[michel.s]

Bro, as per part number this is not the jetronic ECU on your 1991. This is the ABS and ASR control unit. The jetronic ECU must be behind i guess.
Check this link it describes your part number:

ePartsLand - Mercedes w124 E300 320E ASR ECU ABS Computer 1245450132

ePartsLand - Mercedes w124 E300 320E ASR ECU ABS Computer 1245450132: Liquid error: invalid integer

www.epartsland.com

 

[augapfel]

Well how about that. I was being lazy and thought I might get embarrassed. Yep.

In my defense every other 124 I have has the M103 and the Jetronic ECU is directly behind the battery. So naturally I assumed that this 91 with the M104 also had the Jetronic ECU directly behind the battery. Aaaand since getting to the modules behind the one I thought was the Jetronic ECU requires unbolting some stuff i tossed the dice. And lost.

At least there's a logical explanation for why the engine started and ran exactly the same whether I connected the original "Jetronic ECU" or the replacement "Jetronic ECU." Oh brother...

Also in my defense (somewhat) the ebay seller that I bought the part from described it as the engine ECU. See for yourself. Ebay item 283912288759 . <sigh>

Now that it's dark when I get home from work it's gonna be hard to advance this project.

 

[LeftCoastGeek]

fleabay, caveat emptor.

 

[michel.s]

Well how about that. I was being lazy and thought I might get embarrassed. Yep.

In my defense every other 124 I have has the M103 and the Jetronic ECU is directly behind the battery. So naturally I assumed that this 91 with the M104 also had the Jetronic ECU directly behind the battery. Aaaand since getting to the modules behind the one I thought was the Jetronic ECU requires unbolting some stuff i tossed the dice. And lost.

At least there's a logical explanation for why the engine started and ran exactly the same whether I connected the original "Jetronic ECU" or the replacement "Jetronic ECU." Oh brother...

Also in my defense (somewhat) the ebay seller that I bought the part from described it as the engine ECU. See for yourself. Ebay item 283912288759 . <sigh>

Now that it's dark when I get home from work it's gonna be hard to advance this project.

No worries brother, such things happen to all of us. I 'll be always ready for help.