GeorgeB wrote:

BlackBox told me that duty or VAT shouldn't be charged on repairs.

Regardless of whether they are or aren't charged, the cost of shipping x 2 plus the repair fee is still mental.

Well, problem solved, after an inordinate amount of time, the problem was.... a transistor. 🤣

In the meantime, my A-pillar connector had gotten even greener and more crusty so couldn't communicate with nanocom at all. Replaced the connectors and back up and running, woohoo.

Yeah I really don't fancy sending nanocom away from the UK anymore, it'd probably end up costing more than buying a complete second hand unit now, post brexit. Wasn't cheap beforehand either.

Teeth on gems are easily bent too.

Haven't had a chance to get a lead yet.

davew wrote:

Fair enough mace, we did ! Perhaps the CKPs in our heads are faulty ??

:D

I suspect we went off on a tangent once you asked about monitoring the EAS handshaking with a 'scope...... which probably won't help (?) At risk of _another _tangent have you tried any other EAS diagnostics too (eg. RSW) ?. As you (may) know the EAS uses a dedicated pair of pins on the OBD connector and that may be the primary problem ??

It's definitely a nanocom problem, other diagnostics can talk to EAS both in multiple vehicles and in my bench setup, hence why I want to check a known working one for it's voltage levels.

Not interested in the actual comms chatter as such for the purposes of this issue.

From my probing, I'm pretty sure the green lead has some level of active electronics buried in it. Might not be much more than a couple of diodes or a transistor though, but hard to tell from the outside. I may see if I can borrow someone elses lead and see if that makes any difference - would explain why my extensive reverse engineering of the nanocom hardware has come up empty.

davew wrote:

mace; If you do get stuck let me know and I will 'scope my (working) CKP and post it up;

I was never stuck WRT CKP :) you lot just hijacked my thread 🤣

Have you got a nanocom?

davew wrote:

It depends Mace/Miah on what you mean by 'way higher' there - as the base noise on that diagram is about 10V and the CKP pulses (only) about 12V - plus this is an analogue (magnetic/AC) system of course. Thus any fault - eg, larger sensor/tooth gaps, bent teeth, cracks in flex plate, detritus etc affecting that magnetic field can easily result in false triggers - eg. the (expected regular) pulse missing (in particular) or causing (less frequently) multiple pulses, thus confusing the ECU/timing.

Hope that helps, if I can find any illustrations (or photos) of a faulty CKP I will post that up !

Maybe I'm misreading that scope output, but looks to me like there is negligible base noise, and the teeth are triggering 4v pulses, with the tooth after the blank triggering a slightly higher pulse at 6v for some reason, perhaps double width?

Unplug switchpack. Scope pins 2, 3 and 4 on the switchpack plug.

I don't have the pin descriptions to hand but one is direction, one is clock and the last one is data.

They should be fairly obvious when you scope them.

So with it unplugged, you'll see data packets, with big gaps between them.

Plug it in and re-scope (just data if you're feeling lazy). Those blanks should now be filled with data packets too.

davew wrote:

EDIT: Had a quick (failed) look for the LR illustration for this signal for the GEMs, in the ETM IIRC (?), but the main point (as the the Jag/Pico diagram above illustrates) is that the peaks are not much higher that the base noise and so the possibility for false trggers is also high.......

Please explain.. The peaks are way higher than the base noise from where I'm sitting?

romanrob wrote:

What's the next most likely point of failure. A fried main chip in the switch pack?

Check for plausible looking two way serial comms. More likely than a dead chip.

Lpgc wrote:

Hope this isn't too far off-subject...

Pretty far, but I'll let you have it :)

On another make/model vehicle I recently attempted diagnosis of an intermittent misfire accompanied with error codes pointing to the crank sensor and sometimes cam sensors, the same codes occurred even with the cam sensors ruled out (running the engine in group injection mode with cam sensors unplugged a fault still occurred pointing to the crank sensor and the revcounter reading that is crank sensor driven fluctuated when the fault was occurring). Using my cheap digital oscilloscope I diagnosed this problem as one of a knacked flex plate, something related to massive crank thrust bearing problem or knacked rear main crank bearing... because when the fault occurred the crank sensor signal connected directly to the scope showed an occasional double width pulse (the flex plate teeth seemed in good order and the same results were repeatable with several different crank sensors). This conclusion seems a little far fetched even to me (I made the conclusion) but when you've ruled out everything else the remaining possibility(s) must be true and I can think of nothing else that could be true in this situation. The car has since been to another 'specialist' (vehicle dismantler rather than diagnostics master in reality) whom, like me, at first suspected a dodgy engine ECU. He swapped and recoded a replacement ECU but the problem remained. The same car will be going back to the scrapman in a few weeks and I'm quite certain that this specialist won't be connecting an oscilloscope... But I do expect he could fix the problem by fitting a replacement engine along with it's flex plate and he has easy opportunity to do that because he has plenty engines lying around. If he ends up fitting a replacement engine I reckon that either the flex plate will be the fix or the engine without mega excessive crank end float would be the fix... and I expect my unusual diagnosis conclusion to be correct.

Interestingly enough, I hooked my scope up to my crank sensor a week or two ago, trying to find a reason for slightly lumpy running. Noticed that most of the signal spikes were the same amplitude, but three or four of them were higher. Took the cover off and very subtly tweaked a couple of teeth which weren't bang on parallel, and it made a big difference to the running. Bizarre, but hey.

My best guess is that the ECU looks for a voltage increase above a threshold, and the faster ramp time on the big pulses was causing it to fire ever so slightly early.

Beowulf wrote:

Wouldn’t a logic analyzer be more appropriate for recording the entire communication? My limited understanding is that a scope is better suited for analyzing repetitive signaling or the signal integrity. I ask because it’s on my someday list of things to do, to grok the P38 wire protocols and bend them to my will.

Absolutely, but I know the comms are there, just that the nanocom appears to be half deaf when it comes to receiving the EAS' reply. It knows it's there enough to not give a 'no comms' error, but not enough to do something useful. So it simply stops responding to any input, and you have to force a power off.

On a related note why couldn’t someone clone the functionality of a nanocom, which itself is a clone of sorts of testbook, by watching the signaling on the wire between the nanocom and the various ECUs? I realize that being able to see the digital signal doesn’t mean you can know the data payload. Exploring this has been on my someday list for a long time.

You'd be surprised.. ;)

What cheap scope would be worth getting for a P38?

I have a Micsig, which is pretty decent, and battery powered so portable. Tbh any scope will be sufficient for working on a p38, there's nothing particularly high speed etc.

Hi folks,

Anyone here got nanocom and also an oscilloscope? My nanocom is playing up talking to EAS, and I'd like to see a known good trace of a chat between the two, to aid finding the fault.

Thanks,

Miah

Shameless plug: If desperate, I can update the mileage on cluster and or BECM. :D

These look like they bypass the vehicle harness entirely, is that accurate? Where does it pick up the reverse signal?

One should have the insert, the other shouldn't, from memory of taking one apart last year.

White smoke could also point to unburned petrol. If you can start it directly on LPG perhaps pull the fuel pump relay so there's no pressure in the rail and see if that changes the symptoms at all.

Not overly familiar with the diesels but if you can get access by removing just one pipe then go for it. As for difficulty starting afterwards, just leave the injector end of the pipe slightly loose and covered by a rag and crank it, should bleed the air out pretty quickly.

Ok tested on my daily, from cold.

From initial start for ~ 5 seconds, trims are at zero, open loop.
For the next 30-60 seconds, it goes closed loop, and the short term fuel trims go up to max (38.75%). O2's are nailed at 5 volts as you'd expect.
After that the trims slowly reduce down towards zero, and the O2's begin switching.

So, it's normal.

Actually it occurs to me that it might be correct that its up at max at startup, that could be the way it does the choke. I'll plug my nanocom in later when I get a moment to check that, but it vaguely feels right.