Engine harness differences 88 vs 89

[Kershaw]

I saw something that caught my eye while trying to diagnose why the engine harness I bought on ebay ('89) is not allowing my car to start. Might be something I forgot to hook up. It cranks, but it has no spark. I can't see anything I missed. edit: put another harness in, now it runs like before. all fine except the wot hiccup at 4500rpm.

Anyways...

I did notice that the diagnostic ports are different between the two. The 88 has one more lead at the 2 o clock position. I thought all engine harnesses were the same? Anyone know why this difference exists?

1988 engine harness

http://imgur.com/wmsXC7V.jpg

1989 engine harness

http://i.imgur.com/Dofum6S.jpg

Weird. Any ideas? Extra diagnostic info?

[nando]

88 has a 153 dme, 89 will be a 173 or later. Funtionally they are the same but the 89 has more diagnostics capabilities. That could be a factor.

I think the harnesses are functionally the same but there are definitely differences in construction.

[Huserdaddy]

http://www.e30zone.net/e30zonewiki/index.php/C101

Check it out. Might answer your question.

Sent from my SAMSUNG-SM-G900A using Tapatalk

[Kershaw]

C101 is not the diagnostic port.

[Julien]

88 has a 153 dme, 89 will be a 173 or later. Funtionally they are the same but the 89 has more diagnostics capabilities. That could be a factor.

I think the harnesses are functionally the same but there are definitely differences in construction.

afaik 88s used 173. Only difference I'm aware of was the 89 had 12v+ ABS wiring that is a ground on an 88. ask me how I know

[nando]

No, 88 is definitely 153.

[Kershaw]

Yeah, I have 153 as my stock DME.

[flyboyx]

i was thinking ix's use a special computer. as far as i know, the difference is that the ix will open the icv if it senses one to 3 wheels not spinning and the engine is at idle or something like that. all of my ix's have a 153 code on the dme but the case is thicker. one day, i took the box apart to see why and it had 2 circuit boards stacked on top of each other instead of one.

i have been under the premise that you can use a rwd dme in an ix but it won't have this minor safety feature?

am i completely wrong on this?



also:

related to this thread but unrelated to the computer:

as mentioned in a previous thread, i swapped the wiring harness out of the '88ix i am restoring and installed the harness from my '91 auto parts car. for some reason, when i connect the battery, the starter will spin continuously without engaging. (to be clear, i pulled an unknown used starter off my parts shelf and installed it in this car) i started to trouble shoot the issue today. i pulled the rubber cover back on the C101. immediately, i noticed that pins 19 and 20 are different between the two harnesses.

the 88: pin 19-brown wire/pin 20-open
the 91: pin 19 open /pin 20 red/yellow stripe wire

i have my doubts this is the reason my starter spins continuously.
i would think the brown wire(pin 19) is a ground and pin 20 on the '91 is probably abs or srs.

i went all through the factory wiring diagrams of both models and i cannot find any information on either pin 19 or 20.

if anyone has any ideas, i am all ears.

another possibility that came to mind is that there is a short inside the starter and the power from pin #7(heavy green wire) is activating the relay. i think i am going to change the starter with one of the spares i have laying around in the shed.

it still doesn't solve my potential harness issue, but we shall see.

[nando]

it's not a special computer. the 1987 and 1988 325i also used a 153. the seta used a 154 which is the same thing with a different tune. the stacked PCBs is just a limitation of electronic designs from the mid 80's. Later they simplified it to a 1 PCB design for 1989 and later E30s.

It doesn't "sense" anything, the extra circuit is literally just a copy of the standard ICV circuit, only it gets it's signal from the ABS computer instead of the DME. On normal E30s it's not hooked up but it's still there. The trigger that turns it on is actually the mercury switch on the front left fender - and all it is really is an on/off switch.

Basically it's a really crude version of ASC that is used on modern cars, but all it can do is add throttle instead of being able to cut it as well.

the reason pin 20 on the later cars is different is because the ABS relay has been moved to the pump, so the power trigger comes through the C101 from the ignition switch.

BTW, it's pin 20 on both sides. it can't be 19 on one side of the C101 and 20 on the other. 19 is the activation signal for the ICV circuit mentioned above. :p

[jeffnhiscars]

i was thinking ix's use a special computer. as far as i know, the difference is that the ix will open the icv if it senses one to 3 wheels not spinning and the engine is at idle or something like that. all of my ix's have a 153 code on the dme but the case is thicker. one day, i took the box apart to see why and it had 2 circuit boards stacked on top of each other instead of one.

i have been under the premise that you can use a rwd dme in an ix but it won't have this minor safety feature?

am i completely wrong on this?



also:

related to this thread but unrelated to the computer:

as mentioned in a previous thread, i swapped the wiring harness out of the '88ix i am restoring and installed the harness from my '91 auto parts car. for some reason, when i connect the battery, the starter will spin continuously without engaging. (to be clear, i pulled an unknown used starter off my parts shelf and installed it in this car) i started to trouble shoot the issue today. i pulled the rubber cover back on the C101. immediately, i noticed that pins 19 and 20 are different between the two harnesses.

the 88: pin 19-brown wire/pin 20-open
the 91: pin 19 open /pin 20 red/yellow stripe wire

i have my doubts this is the reason my starter spins continuously.
i would think the brown wire(pin 19) is a ground and pin 20 on the '91 is probably abs or srs.

i went all through the factory wiring diagrams of both models and i cannot find any information on either pin 19 or 20.

if anyone has any ideas, i am all ears.

another possibility that came to mind is that there is a short inside the starter and the power from pin #7(heavy green wire) is activating the relay. i think i am going to change the starter with one of the spares i have laying around in the shed.

it still doesn't solve my potential harness issue, but we shall see.

Starter solenoid is just a big relay energized by the ignition switch. either the activation wire is hot when it shouldn't be or the solenoid is just stuck and should be replaced.

[flyboyx]

it's not a special computer. the 1987 and 1988 325i also used a 153. the seta used a 154 which is the same thing with a different tune. the stacked PCBs is just a limitation of electronic designs from the mid 80's. Later they simplified it to a 1 PCB design for 1989 and later E30s.

It doesn't "sense" anything, the extra circuit is literally just a copy of the standard ICV circuit, only it gets it's signal from the ABS computer instead of the DME. On normal E30s it's not hooked up but it's still there. The trigger that turns it on is actually the mercury switch on the front left fender - and all it is really is an on/off switch.

Basically it's a really crude version of ASC that is used on modern cars, but all it can do is add throttle instead of being able to cut it as well.

the reason pin 20 on the later cars is different is because the ABS relay has been moved to the pump, so the power trigger comes through the C101 from the ignition switch.

BTW, it's pin 20 on both sides. it can't be 19 on one side of the C101 and 20 on the other. 19 is the activation signal for the ICV circuit mentioned above. :p

awesome. good info about the dme.

as far as the wiring harness goes, the 88 harness has a pin 19 and no 20. the 91 harness has no pin 19 but it does have a 20. sorry if i wasn't clear.

[nando]

Actually I remembered incorrectly. Pin 17 is for the ix ABS signal.

Pin 19 is for the M3 temp signal. So I don't have any idea why your ix had that wire there!

If 19 had a brown wire and 20 was empty, there's no reason the '91 harness wouldn't have worked. the '91 shouldn't have a pin 19 and there's nothing going to 20, and it wouldn't stop the engine from starting either.

The only C101 pin that is NEVER used FYI is pin 3. :)

[Julien]

Maybe Ix's are different but when I ran:

88 harness in a 91 the ABS light came on and I had to jumper a wire to fix it
91 harness in a 88 there was a light fire :-O

But these weren't AWD e30s

[flyboyx]

well, after checking the pins on the c101, i have my doubts the starter problem is due to the harness. i think perhaps the contractor in the starter might be stuck. my next step will be to change it out.

the starter i am presently using came with an engine i bought out of a junk yard to put in my son's car. it could perhaps be the reason it was there in the first place.

thank you for the info above julien. i'll take a look at those two dissimilar pins and compare them to the wires on the body harness to make sure i don't run a ground into line voltage.

[nando]

yeah as long as you don't hook the 91's pin 20 to anything in an '88, it will work. you could just clip it from the engine harness side and tape off the stub. the '88 has it's own power for the ABS so it doesn't need that pin.

If only I could count on pin 20 being a ground on most early cars, that would make building M50 adapters a heck of a lot easier..