75ZT Community

I've been tinkering the last few days of wiring up some ECU (Engine Control Unit)'s on the bench and trying to communicate with them. However I'm failing somewhat miserably at the moment as I can not get any comms down the K-BUS.

Does anyone know which ECU's need to been added as a minimum for communication to take place. So far I have;

IPK (Instrument pack (IPK from the German))
EWS (Engine immobiliser (EWS from the German, Elektronik WegfahrSicherung))
ECM - NNN000179
LSM (Light Switch Module)

All grounds, perm and ign lives and KBUS and the Canbus from IPK to the ECM. The IPK and LSM light as normal and the EWS is working as the "Engine Disabled" message appears. However nadda from the KBUS. The T4 (Testbook version 4.Computer Diagnostic System) isn't on it yet as I don't want to short it out by spiking the KBUS or something stupid. I have another diagnostic kit on it that reads from the KBUS only.

Anyone any ideas? :}

You ought to be able to get it working as a kbus with just a very few items. However a kbus pull up resistor is required for operation, and I have a feeling it's in the BCU (Body Control Unit) though I may be wrong. I've had as few as two items and made communication work.

What's the voltage on Kbus? Do you have a scope to look at any waveforms?

No, no scope available. I've just left the office and at somewhere else now and left the setup. I've read there is a resistor in the BCU on the KBUS, 4.7K should do the trick IIRC. Didn't realise it was used as a pull up resistor though, if I put one inbetween the K-Bus and +12V I might be in luck. Going to have to wait now till tomorrow for further testing!

If you want to borrow a silly-scope, just let me know David.

Yes, between kbus and battery. 4k7 sounds right and I couldn't remember where it lived on the car.

If you are right and it's the BCU which I seem to remember too, that will give problems without it for sure. If I can find one of my link harnesses I'll check the value I used.

Cheers for the offer Paul, I'll see how I get on.

Hans on the OC has stated he uses 10k. I have some 4.7k, and some 5.1k so I'll see how I get on, I can always put the BCU in. I only want to try to talk to the ECU at the moment