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Discussion Starter · #1 · (Edited)
This started overnight; drove into the garage fine, next morning: spin spin spin with nary a pop.
The most recent work on the car was several months and hundreds of miles back, fitting a replacement JBE to add Servotronic steering.

Short VIN: A951286
The battery is strong, and I have a high-amp battery charger hooked up in addition. Battery voltage is ~ 13.5
Ista+ connects to the ECM, and reports these codes: 2ACC 2ACB 2E85 6E24 5F77 A0B4
The Ista test plan goes first to the K6300 DME power relay, and basically says, "replace it". But I believe this relay is integral to the 'power distribution box' (fuse box) behind the glove compartment, and not separately replaceable. So I'd like to dig in a little farther before buying a new fuse box.

With the key in, ignition on, there's no voltage at Fuse37. That should be battery voltage, roughly, coming out of the K6300 relay.
=> so either the relay has failed, or it's not getting power+ground to activate it, or there's no power on the "input" side of the relay.
  1. Looking at the power+ground to activate the relay first.
    1. Power I think comes from Fuse 4 through the ECU. Edit: nah, power to activate the relay comes from the large red cable going into the power distribution box.
    2. Ground I think comes from a red/gray wire coming out of the ECU.
      I back-pinned the connector in position 5 of the X6011 connector found in the white plastic DME box on the passenger side of the engine compartment. Then I grounded that pin. There was still no voltage out on Fuse 37.
      I read somewhere that power out of Fuse 4 into the ECM is required for the ECM to provide a ground signal. I checked Fuse 4; there is battery voltage available at its connections in the fuse box behind the glove box, and the fuse is good.
    3. I guess I'll hook the multimeter to that pin, and see if it goes to ground when the key is on? That would make me think the ECM was 'doing the right thing', that is: that the ECM is commanding the K6300 relay to activate. The next step... dunno.
Happy to have others' thoughts and advice here.
(the JBE error in that shot is due to me unplugging the air quality sensor from the area of the white plastic ECM box)
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Discussion Starter · #2 ·
OP here. Am I wrong to try putting a sizable jumper (fused) from a Pin 30 source into the output of Fuse 37? This would simulate the closing of the K6300 relay.
 

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Discussion Starter · #4 ·
Thanks for that, @gbalthrop. Looks like I'm going to add to the 'Most frequently-reported cause' count.

With the ignition on, I applied chassis ground to X6011/5 (the other end of the red/gray wire that terminates at X11010/1). Now Fuse37 shows battery voltage, and the engine starts.
So I'm happy (well, happier) with the state of the K6300 DME power relay, but must go looking for the cause of "no ground signal" somewhere between the X6011 connector and the ECM. Or, I supposed, inside the ECM.

I'll move my chassis ground to the X6005/13 connector on the ECM itself, and repeat the voltage test at Fuse37. Assuming that gives a positive result... am I pulling the ECM next?

A thought: could a fault in ComfortAccess or the 'Immobilizer' system be convincing the ECM to withhold the ground signal? Or do those systems' contributions to startup happen prior to this stage?
 

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Discussion Starter · #6 ·
Well, with the X6011 connector in the E-Box disconnected, ignition on:
  • no continuity to ground on the X6011 receptacle pin that runs to to ECM connector/pin X6005/13.
  • a chassis ground applied to the red/gray wire in the X6011/5 plug/pin does activate the K6300 DME power relay, and Fuse37 has battery voltage.
It's still possible that the wire between X6011/5 and X6005/13 is broken. I'll test it for continuity tomorrow (but everything inside the E-Box looks pretty nice thus far).
Otherwise... <points finger at ECM>

Thanks again for your detailed and logical suggestions.
 

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Discussion Starter · #9 · (Edited)
First, the remaining facts:
  • there is continuity all the way between X6005/13 (at the ECM plug) to X11010/1 (plug at the power distribution ("fuse box") behind the glovebox).
  • there is continuity between X6005/13 (the pin itself, in the ECM receptacle) and the 'tie point' on the ECM printed circuit board (PCB).
Those two leave our fingers pointing at the ECM itself, somewhere "upstream" of that tie point on the PCB. The pins in the ECM receptacle look perfect.

I'm not (myself) going to go further in the ECM, as I'm simply not qualified to repair ... whatever is wonky. I'm evaluating options for professional repair of ECM, or procuring a new replacement ECM (with all the attendant synchronizing with the EWS)...

Second, I thought of an alternate version of the 'toggle switch' fix, using an automatically triggered standalone relay:
  1. The coil of the relay would be connected to chassis ground and to a power source near the X11010 connector that has BAT+ when the ignition is on.
  2. The "input side" of the relay would also be connected to chassis ground.
  3. The "output side" of the relay would be tee'd into X11010/1 (the red/gray wire that the ECM grounds to activate ("close") the K6300 DME power relay).
Then, when the ignition is on, the standalone relay will activate, and make a connection between chassis ground and X11010/1 (similarly to the ECM's own action).

Third, some pictures of the E-Box, ECM connectors, & similar in the next post.
 

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Discussion Starter · #11 · (Edited)
Fixed! (maybe)

So I put the sheetmetal cover back on the ECM, sprayed electrical cleaner on the pins & plugs of everything in the E-Box, re-installed the ECM and all the other connectors in there, and hooked up the battery.

Meanwhile, my local independent BMW repair shop called with an idea, which (very roughly) goes like this:

A 'bit serial data' bus connects a number of components in the car, including some components implicated in the error codes posted above. It is possible to re-set (or did he say, "take down"?) the BSD bus by un-plugging the Intelligent Battery Sensor (a small connector on the negative battery terminal).

I unplugged the IBS. The car started. Great! However... when I shut it off and plugged the IBS back in, it also started. So it's not a smoking gun yet.
I'm going to clear the codes and do some driving, expecting that some codes will reappear.
 
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