Wiring diagram - advice please (photos)

[SD1too]

Originally Posted by goltho

I wasn't surprised to find C0449-5 blanked off ...

Originally Posted by goltho

So I need to check the signal to C0895-5 whilst driving?

Yes. You could, of course, just activate cruise and press 'set'!

Fingers crossed.

Simon

PS I'll be incommunicado for a hour or so soon. Don't think I've lost interest!

[goltho]

Originally Posted by SD1too

Yes. You could, of course, just activate cruise and press 'set'!

There's a +6.26v signal from the ECM to C0895-5 whether or not cruise is switched on. Pressing set makes no difference (it wouldn't, the car was stationary). I didn't drive and test as it involves some shenanigans; I thought I'd have some lunch for a change and await your valued input.

What +6.26v means, I have no clue.

Dougie.

[SD1too]

Originally Posted by goltho

What +6.26v means, I have no clue.

Your meter can't read the square wave properly so it gives you an average voltage reading. The actual values will tell us very little. What is important is that the digital signal is now reaching C0895-5.

After lunch please go for a test drive and see if cruise still doesn't work. I'll check-in with you later this afternoon.

Simon

[goltho]

Originally Posted by SD1too

After lunch please go for a test drive and see if cruise still doesn't work.

I did with assistance to ensure accurate reporting. Another twist. The +6.26v drops to +0.56v when the car is shifted out of neutral or park into any forward gear. Needless to say, cruise did not work.

Dougie.

[SD1too]

Drat and double drat!

I'll have to look at this again either late tonight or tomorrow morning.

Simon

[goltho]

Originally Posted by SD1too

Drat and double drat!

I'll have to look at this again either late tonight or tomorrow morning.

Thanks Simon. I'm about to get my spade out too.

Dougie.

[SD1too]

I forgot to ask, did the IPK cruise logo still fail to illuminate?

Simon

[goltho]

Originally Posted by SD1too

I forgot to ask, did the IPK cruise logo still fail to illuminate?

Yes, it failed to illuminate.

Dougie.

[SKS Disco]

Originally Posted by goltho

I've not managed to contort yet to see. But as it's talking to the EAT (and now the cruise relay) correctly, I've little reason to doubt it's faulty. So I'm currently stuffed.

Dougie.

Hmmm, Wonder if your ZCS codes are configured for Cruise? If you do all original wiring and connectors the ECU says "no" It does not know where to send the signal.

[goltho]

Originally Posted by SKS Disco

Hmmm, Wonder if your ZCS codes are configured for Cruise? If you do all original wiring and connectors the ECU says "no" It does not know where to send the signal.

The ZCS codes should be configured for cruise as I drove a couple of hours to Jamie's last weekend for that job on his T4. He told me it all configured ok except for the one half of the brake switch, as we've seen. I've run TOAF several times since to check errors, and the three ECUs which I understand need to be told of the cruise existence, do now show cruise on their config displays. That's as far as TOAF goes though.

I've found nothing online referring to cruise control being affected deliberately or otherwise by automatic transmission gear positions. From distant memory though, isn't it the case that if you slip an auto into neutral whilst cruise is engaged, it disengages it? The fact that moving into gear from neutral drops the voltage seems illogical to me but I have no idea how the ECM is designed to talk to the cruise relay, or even if the voltage is supposed to change relative to the transmission state.

I think if we've reached a natural pause in diagnosing, I should revisit and recheck everything I've done. I suppose it's not outside the bounds of possibility that one of the cruise modules is faulty either.

Dougie.