Getting sick of CEL chasing...

[nrubenstein]

I've tried multiple ECUs and I still can't get rid of the control unit supply code.

This has been the only thing standing between me and registering this damned car for well over a month now, and I'm really getting tired of it. Does anyone have any ideas?

[jrdeamicis]

Have you tried swapping ECUs?

[lennon]

I've tried multiple ECUs and I still can't get rid of the control unit supply code.

Have you tried swapping ECUs?

...

sorry i cant help op

[jrdeamicis]

Oh sorry, usually I skip the first sentence. Its usual total bullshit.

What is your battery voltage w/ car running and off?

[jrdeamicis]

Where is your ECU getting voltage from? Fusible Link?

What is your ground for the ECU?

[nrubenstein]

The ground is on the shock tower, the voltage supply is from the distribution block.

Voltage with the car off is 12.4, car on is 13.9.

If you'd point me in the direction of the fusible link, I'd happily check that.

[jrdeamicis]

The ground is on the shock tower, the voltage supply is from the distribution block.

Voltage with the car off is 12.4, car on is 13.9.

If you'd point me in the direction of the fusible link, I'd happily check that.

13.9 seems a bit low for the car on...

The fusible link is the smaller wire that is piggybacked with the B+ on the car coming from the battery. Look for +12V on that wire. Also your ECU should be on that fusible link power.

[nrubenstein]

13.9 seems a bit low for the car on...

The fusible link is the smaller wire that is piggybacked with the B+ on the car coming from the battery. Look for +12V on that wire. Also your ECU should be on that fusible link power.

Ah, I'd swapped it off of there to see if that would help. I'll put it back on.

13.9 is pretty normal for me. Every BMW I've had has been in the 13.8-14 range and it IS a new alternator.

It finally occurred to me that I can register this thing as historic until I figure this out, so that's a plus at least.

[matt]

You can't just pass a sniffer with a CEL on?

[nrubenstein]

You can't just pass a sniffer with a CEL on?

CEL = automatic fail.

Edit: And they check to see if it works.

[b*saint]

So voltage at the supply pin on the ECU connector is 13.9 volts when running? How did you check that?

[matt]

CEL = automatic fail.

Edit: And they check to see if it works.

Interesting. I've passed I don't know how many times with a CEL. On an OBD1 car it shouldn't matter IMHO.

The control unit memory test could be a bad checksum in your chip. Have you swapped chips?