Different ECU

[berlow94]

I'm aware of the different ABS system that IX's came equipped with. The additional mercury "acceleration" sensor and it's "ice mode".

But does anyone know why IX's have different ECU's than the rwd M20 powered cars? I'm not aware of any different sensors or electronics on the IX M20 vs rwd M20. Something to do with engine braking braking for the awd system? different control of the ICV?

[MrBurgundy]

88 and up use a 173 if im not mistaken, the early models used the 153.

[Kershaw]

My 88 came with a 153.

[packratbimmer]

All of the automatics I have owned had the 351

[kid325e]

Interesting topic.

Never heard of ice mode or the Mercury acceleration sensor. What do these do? Without the 173 you don't get these "features"?

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[Kershaw]

IIRC it's a separate little module that sits right in front of the fusebox.

[Chrisbike]

I have a 524 ecu in my 91' iX airbag

[Max325ix]

I am no expert and somewhat new to the IX and E30 but not new to older BMW's.

Perhaps the different ECU in the IX's is related to the function of the ABS with AWD system. At the time when new the E30 325ix was the only vehicle on the market that allowed the ABS to function with or while the AWD is active. The Audi quatro of the era did not.

Max

[Kershaw]

I think they correspond to the years roughly and sometimes randomly. 173s have more functionality, like checking CEL codes, than 153, for example.

[nando]

There is nothing ix specific about any ECU. Any motronic 1.1/1.3 will work. the "ABS" feature is nothing more than an on/off switch input into the ICV circuit, which is present on all E30 DMEs.

The one exception is early 153s had an issue with the input voltage from the ABS circuit being slightly out of spec. Some of these cars were fitted with a resistor which fixes the problem.

Again, there's no such thing as an "ix" DME. In fact, all of the hardware from 173-526 are identical. AFAIK, the 5XX DMEs were for cars sold in the California emissions market, but there's no other difference.

[101]

Here's an interesting read from the Pelican site on the different ECU's:

http://www.pelicanparts.com/bmw/techarticles/E36-DME-Repair/E36-DME-Repair.htm

The 153's are Motronic 1.1 and do not have stomp test functionality. 173's and up are all basically the same as Nando said. I've run 173, 380, and 525 successfully in my IX.

Here's info from a BMW service bulletin that describes the additional capabilities of the iX ABS system. The bulletin only applied to certain 1988 model cars, but the description of the functionality is accurate ...

BMW SERVICE BULLETIN #34-02-89 (1857)
SUBJECT: ABS Warning Lamp Illumination
MODEL: 1988 325iX (up to and including 5/88 production)

Observation: The ABS system on the 325iX incorporates an additional function to reduce engine braking (at closed throttle) when ABS is activated on low drag coefficient road surfaces.

The ABS Control Unit sends this request via pin 3 to pin 50 of the DME Control Unit.

As part of the ABS self-check, this circuit is continuously monitored. if the control unit determines that the circuit is open or has high resistance the ABS system will be deactivated and the ABS warrning lamp will be illuminated

Situation: Tolerances in DME circuitry (pin 50) can cause this condition to occur. An adapter harness is available to compensate for these tolerances. (BMW Part No. 12 57 1 724 368)

DME 1.3 control units do not have circuitry compatible with the ABS control units originally installed in these vehicles. For this reason an adapter harness must be installed whenever a DME 1.3 control unit is installed into one of these vehicles.

DME 1.1 control units may also exhibit the same problem To determIne if the problem lies in the circuit (or elsewhere In the ABS system) perform the following diagnostic steps.

Note: Call up the DME system via the BMW Service Tester for
positive identification of the control unit (1.1 vs. 1.3).

Diagnostic Procedure
Tools required:
Universal Adaptor w/35 pin adaptor leads
Fluke muitimeter

* Connect universal adaptor between ABS control unit and harness

* Connect multimeter between pin 3 (+) and pin 10 (-).

* Start engine and observe voltage.

* If the voltage is 1.23 or higher an adaptor harness must be installed.

If below 1 .23 V the problem is elsewhere via the ABS system. Use the BMW Service Tester to diagnose the system.

Harness Installation

1) Disconnect engine harness from the vehicle harness at C1O1

2) Remove the connector holder from the firewall and install the additonal mounting bracket.

3) Install both connector holders to this bracket.

4) Connect adaptor harness between the engine and vehicle harness.

5) Secure connector housing in the appropriate connector holders.

6) Attach the ground lead on this adaptor harness to the hood catch

WARRANY INFO: Defect Code 34 53 00 12 00




And finally here's a site that every IX owner should have bookmarked ... older, but lots of good info within. I refer to it frequently.

http://home.earthlink.net/~hainesinutah/iX/index.html

[nando]

The adapter harness mentioned in the above TSB is basically just a resistor. I discovered all this when I went to hook up the "ABS input" into my Megasquirt. It was then that I realized how simple the system is, and realistically - you don't really need it at all.

[Kershaw]

That's really interesting. I had an odd issue a few weeks after I tried to fix my ABS, finally. I drove to my friends apartment and as I pulled into a spot the brake pedal froze solid, I felt some odd thumping, and I couldn't stop the car. As soon as the front wheels were straight I could move the pedal again and I slammed down on the brakes. I immediately reached under the dash and removed the damn ABS relay.

I have an early 88, 10/87, could this be the cause of my ABS snafu? Or something else? I am not keen to try to hook up the ABS anymore. That shit was scary.

[kid325e]

I've felt the same thing but I wouldn't say I felt like the car didn't know what was happening. I thought it was just the ABS at work as designed.


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[zaq123]

The adapter harness mentioned in the above TSB is basically just a resistor. I discovered all this when I went to hook up the "ABS input" into my Megasquirt. It was then that I realized how simple the system is, and realistically - you don't really need it at all.

Nando,

old post but can you give more details on the resistor? Did you just ground pin 50 with 1k resistor in MS antdthat took care of ABS light?