I've had an issue previously after some welding work was done (this is actually on a Disco 2 but its the same part used on the p38) where the inertia switch was tripped, this gave a few symptoms as follows
Failure to start (Cranks but not firing)
Hazard lights flashing when trying to start
Diagnostics fail to connect

Above was obviously sorted by resetting the swtich. However that was several months ago, Today I've driven the car around 35 miles and around a mile from the end of the journey pulled up at traffic lights. On pulling away car suddenly isn't running right (its been fine prior to that) Limped it the last mile or so and left it for a bit at that point.

Tried to start it a couple of hours later - LPG system is in protest mode (beeping) and engine clearly isn't running right. So out comes the Nano - which will not connect to the engine ecu no matter what I try (its been fine previously). So fire up the diagnostics for the LPG and find thats its complaining of several errors, some of which are probabbly from the original inertia switch incident, but 4 current ones are "petrol injector no signal on channels 2/4/5/6" which would explain the symptoms. live readings also show 0 for those 4 channels (2 and 4 would be the drivers side bank, 5/6 the front two on the passenger side bank)

My first thought was damaged wiring, but I think this unlikely as theres no obvious evidence of any damage, and for all 4 to fail like that seems unlikely. It also wouldn't explain the lack of diagnostic connection though the Nano either. I don't have anything unusual happening with the hazard lights on this occasion either.

I've checked Rave, but it has very little to say about the switch or how to test it. There seems to be 3 wires to it, does anyone know how the connections should be if checked on a multimeter or how it actually works? Or is it possible to bridge out connections to remove it as a possibility? If it was 2 or even 4 connections it would make more sense to me, but 3 doesn't give me much of a clue what it should be doing without another to compare it to?

Or does anyone have an idea of something common to both systems that could be causing the problem? Its a 2000 Thor 4.0 if it makes any difference. Obviously a lot of the bits differ between the p38 and the D2 but I'd imagine the basic engine electrics are fairly similar?

Uhm, I remember playing with this as I used the inertia switch to make a poor's man anti-theft while it was in the old garage.
I can look physically at the wiring in the afternoon, but by seeing quick in the ETM one wire sends the cut-off signal to engine electrics (should be 1, white/orange), one is the signal to BeCM (should be 2, white/purple), and 3 is the signal to the fuel pump cut-off (white/blue).
I remember making a switch between two of these, don't remember which though, and you basically "lie" to the car about what state the inertia switch is.
If you are bold, and have no time, clear the footwell area and start hacking away no fear, worse case scenario is "does not start" :-)

Not sure if the wire colours will be the same but on the P38 you've got a White/Orange on pin 1 which is a power feed straight from the fuel pump relay and a White/Blue which goes to the fuel pump through the contact in the inertia switch on pin 3. The contact is a changeover so under normal operation these two pins are connected together so power from the fuel pump relay goes directly to the fuel pump. The third wire on pin 2 (a White/Purple) goes to the BeCM to tell it if the switch has operated. Under normal circumstances, this is open circuit but on impact, the changeover contact connects it to the fuel pump. So it disconnects the power and supplies the BeCM with a ground via the fuel pump.

Hmm, looks like it isn't likely to be that then. Will have to have a look over the wiring as the fault is obviously there somewhere, I'm starting to think its like something has come unplugged from the ecu given the amount of faults its showing and lack of diagnostics as well.

Sorry I had a day from hell and returned only a while ago. Will check tomorrow.
In any case from memory, a non-functioning or "triggered" inertia switch can also negate engine start, nothing else.
I think your errors could be from something else.

I suspect your right, its the lack of diagnostic connection thats got me more puzzled. Will look at it later in the week.
Seems I'm having similar times - Just been looking for the only key to another car, to discover it in the trouser pocket of yesterdays washing.....

I don't know if the Nano gets it's power from the OBD socket? Or if it doesn't whether or not it signals there is power to the OBD socket (if it gets it's power from OBD the obvious signal would be it wouldn't even turn on if not connected to OBD but if it doesn't get it's power from OBD it will turn on anyway but is there some way it signals there is power at the OBD)? Does a different code reader that gets it's power from the OBD socket at least turn on if plugged in?

I haven't looked at any wiring diagrams... But as memory serves I believe the Thor has a separate positive feed to injectors on bank 1 versus bank 2? Implying that at least the problem for several cylinders being reported as no injection pulse by the LPG ECU could be explained by lack of positive to respective petrol injectors. The problem with that theory is that LPG ECU channels 2456 probably don't all fall on one cylinder bank unless you've wired the LPG petrol injector break wiring up unusually. I don't know where the OBD port gets it's live feed from but would doubt it'd be from the same positive feed that provides 12v to petrol injectors on one of the banks.

Did this car previously have an LPG mixer system fitted?

Ahh I was thinking Gems in the point about Thor... But maybe they both have separate positive feeds to injectors on different banks (at least as far as a joint in wiring near the firewall)?

Nano gets its power from the socket yes.

Thanks Chris.

Apologies if already said but is it a case of no power to the OBD socket, or power is there (so Nano comes to life) but still no coms Bri?

Power is there - Nano comes to life, it just won't connect to the engine ecu (this did work prior to the recent incident as well).

I've not tried to another ecu in the car, will give that a go when i get back to it again (its not currently at home).

On the lpg front - its definitley had a previous conversion, which definitely had 8 spuds installed in the upper manifold and a hole for the filler in the lower section of the rear wing. This had long gone by the time I got the vehicle, and the guy I brought it from described it as having an lpg tank (which was actually an air tank as it was far too small to be useful as an lpg tank and wrong valvework on it) but no other signs of conversion. I couldn't guarantee that it only had a multipoint system on it and didn't have a singlepoint before. I don't recall seeing any sign of old injector cuts when it was converted with the KME kit but that may be that the wiring was broken into somewhere else.

I'm guessing your thinking an old injector emulator might be still in there somewhere and now misbehaving?

I'm fairly sure the lpg loom goes 1-4 on the drivers side bank, and 5-8 on the passenger side. I remember there being two lots of wires for injector cuts and fairly sure they got installed like that.

Yes, an emulator or perhaps just a relay that broke the positive connection to petrol injectors...

Easy enough to recheck how you did petrol injector breaks... If channel routing is OK then petrol injector breaks must match respective gas injector outputs and you can see which engine cylinders gas injectors are piped to (heh sorry for teaching sucking eggs).

But it has been working fine (I assume), so it isn't going to be a wiring fault. Doubtful it had a singlepoint on it in the past, not on a Thor.

Don't forget that different modules use different pins in the OBD socket, so just because diagnostics won't connect to one system doesn't mean it won't connect to others. I know it's a D2 but if it was a P38 it could be a water leak meaning half the pins have rotted away.

It would be easy if I'd done them at a more accessible location! Lesson learnt there, it means taking the upper manifold off if we get that far into it again.

Water leak a possible one - the leak in question was a small hole at the drivers side of the windscreen thats now been filled in so isn't leaking anymore (suspect it was a case of paint scraped off when windscreen was changed prior to my ownership)

Connector looks fine though know what your saying about the connection to some are different pins to others (don't think the D2 is quite so bad in that respect, partly as it has less to connect to in the first place).

I do wonder if it had a metering head type lpg setup on it previously though rather than a true single point setup.

Yes it was working fine up until Sunday evening - Drove around 35 miles in it no problem at all and it literally went as I went to pull away at a set of traffic lights, would barely move from standing and its stayed that way since, It takes longer to actually start, runs badly when it does start and has no power at all (As you'd expect given it seems to not be chucking any fuel in half of the engine really).

Can only see it being a wiring fault due to damage, and theres no noticable evidence of that as yet. I did find on Sunday evening that what I can only assume to be the engine ecu in the drivers footwell on the inside of the wing, appears to be loose for some reason. Couldn't see anything obviously disconnected there, but thats where I guess i'm going to have to start looking when time permits to do so.

Looking at the wiring diagram for the gas ecu, its got two bundles of wires 1-4 and 5-8 as you'd expect, so can't see I did anything different there that could suggest either the ecu itself or the harness.

Faults not currently present
P0175 Additive adaptive mixture Correct TRA bank 2 Drive cycle B occured 1 times
P0172 Additive adaptive mixture Correct TRA bank 1 Drive cycle C occured 1 times
P1300 Catalyst damaging misfire, Multiple cylinders drive cycle C occured 4 times
P1301 Catalyst damaging misfire, cyl 1 drive cycle C occured 4 times
P1000 Catalyst damaging misfire, cyl 8 drive cycle C occured 4 times
P0301 Catalyst damaging misfire, cyl 4 drive cycle C occured 4 times
P0303 Catalyst damaging misfire, cyl 3 drive cycle C occured 3 times
Currently present
P0300 emission relevant misfire, multiple cylinders drive cycle C occured 1 times
P0301 emission relevant misfire, cyl 1 drive cycle C occured 1 times
P0308 emission relevant misfire, cyl 8 drive cycle C occured 1 times
And a really odd error
"NA
Occured 0 Times
Signal Too Low
Fault is currently present
Fault determined as intermittent"
And the same but 193 times
And another 193 times but too high

I don't know what to make of the last three messages - I can only guess this is a bug with the Nano? Either way, the intertia switch is ruled out, Will check it with the mutlimeter and confirm what should be seen in the tripped and normal state for info here.

Well the inertia switch seems to have a common pin (C) and this under normal mode should be connected to the pin at the other end of the connector. In the event its tripped, this connection is broken and the c pin connects to the middle pin instead.

Its looking like the fault above is something being caused by the LPG system - I've cut and rejoined the 4 cylinders halfway along the loom (As to do so at the point they actually interrrupt the petrol injector wiring is under the upper manifold - Not a mistake I'd make again on the Thor, it was a pain breaking into them there and would be much better to come further back on the loom).

It now runs just fine on petrol with the other 4 still connected (it obviously won't run on gas like that, nor does it seem to even try swtiching over as it currently stands)

This was tried as when I attempted to start this morning it appeared fine (with cold engine) and on checking further the lpg ecu was showing signals from 7 of the injectors (the 8th one I'd already disconnected which was injector 2 to try and see if I could tell any difference as I knew which one that was and could get to those wires easliy, not that it seemed at the time to make any difference though that was only with holding the wires together).

I'm guessing its looking like the LPG ecu has failed in some way as there doesn't seem to be any sign of any obvious wiring damage, the connector looks fine when seperated as well.

Interestingly the petrol ECU in the footwell, has definite signs of having had things done to the wiring at some point - several rejoined wires there, I guess this may be where the previous conversion was tapped into at some point. Having cut all the insulation tape off, there doesn't appear to be anything amiss there (and given it runs having done the above, other than it looking awful and needing retaping there can't be much wrong there).