MK7 2.4 TDCI problems again

[arrolman]

Hi all,

Had ongoing saga of van not wanting to switch off a while back, surprisingly it stopped after I had changed the wiper switch on the steering cowl. However, back to square one again. Same problem but seems to be getting worse. Van had totally flat batteries a few weeks back, AA man came out and said there was a drain but batteries/alternator was all good. Had no further problems until few days ago when van wouldn't switch off again, unplugged wiper switch and all worked as normal . Now today, used all day no problem until an hour go, took 3 times to start. Once started drove fine, got to B&Q, switched off and back on again few times to make sure it would start. It did. Spent 40 mins in B&Q and now won't start . Can't see any obvious problems but dash has lines through it and all warning symbols are lit. Won't even attempt to start, as though batteries are dead but been used constantly for weeks so cant see how . f*** typical when rammed out with work

[Airthies]

Wiggle the key while you try and start, I suspect the ignition switch is at fault rather than the wiper stalk.
My guess is you've disturbed the ignition switch and plug as you've been doing the wiper stalk and this has worked in your favour.

Push comes to shove take ignition switch off back of barrel and turn it manually with screwdriver or another key etc while the van key is in the ignition Barrel.

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[marcrbarker]

This reminds me so much of a vehicle I looked at with electric gremlins. Peculiar things like the headlights would flash randomly while on the road - and the engine wouldn't turn off. And there was occasional battery drain. I'm not saying this is the same problem you have but with this car was in the end just a little spring clip had broke off inside the stalk and it was bridging between circuits. Again, not saying this is what you have but another car (mine this time) after a roadside 'silver foil round fuse' quick fix wouldn't switch off after key off, because the foil repair was shorting to an adjacent fuse.
So what I'm saying is rather than a broken connection somewhere or something stuck, it could likely be a 'sneak-path' bridge fault between the live feeds. Some live feeds are supposed to be dead when turned off.

Dash has Lines through it??? By the way with car batterys, after a one-time 100% depth discharge they only recover about 5 % of capacity no matter how long charged for, and voltage tests by roadside recovery will report the battery is 'fully charged'. If there's a drain draining away while you're in B&Q for 40 mins, that could had flattened the battery much faster than it drained before the 100% flat event happened.

[arrolman]

So far ignition barrel/ignition switch and wiper switch have all been replaced. All earths cleaned. All electrical connections cleaned. Both batteries have been tested along with alternator and all good. AA man came out, put diagnostics on it and it started. Ran fine for ten mins. Switched on and off twice and fired up. 3rd time wouldn't start again. Diagnostics back on, cleared codes, started again. Whilst we were both looking g at each other outside the van it cut off. Diagnostics on, cleared codes, started. Chanced driving it 3 miles home and it tried to cut out 3 times, as though someone had turned Ed off the ignition then back on again . Losing the will to live

[marcrbarker]

When you say "tried to cut out 3 times on way as though turned off key" is that "off" like the electrics turn off, (interior light comes on? ) heater blower stops and no indicators etc? I mean like someone turned the key?
Or had engine conked out leaving the electrics on?

And are you sure the act of clearing the codes is part what made it restart again? Or maybe incidental?

[arrolman]

As though someone switched ignition off then straight back on. It won't start unless codes are cleared, starts and can stop/start once or twice then refuses to start again until codes are cleared. Got an auto spark coming to have a look tomorrow

[Airthies]

As though someone switched ignition off then straight back on. It won't start unless codes are cleared, starts and can stop/start once or twice then refuses to start again until codes are cleared. Got an auto spark coming to have a look tomorrow

What are the codes.

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[arrolman]

Codes are:

B1D17- BATTERY BACKED SOUNDER - DISCONNECTED
U0100- LOST COMM WITH ECM/PCM
B1051- WASHER SWITCH - DICONNECTED
U0410- INVALID DATA RECEIVED FROM ECM/PCM
C1A92- LEFT REAR WHEEEL SPEEED SENSOR
WP2563- TURBOCHARGER BOOST POSITION SENSOR A CIRCUIT RANGE/POSITION
P0299- TURBOCHAGER A UNDERBOOST
P068B- POWER RELAY DE ENERGISED TOO LATE
U01400- LOST COMM WITH BCM
U0121- LOST COMM WITH ABS CONTROL MODULE
P068A- ECM/PCM POWER RELAY DE ENERGISED TOO EARLY
U0167- LOST COMM WITH IMMOBILIZER CONTROL MODULE
P0299- TUBOCHARGER A UNDERBOOST CONDITION
P2563- TURBOCHARGER BOOST CONTROL POSITION SENSOR A CIRCUIT RANGE/PERFOMANCE
P2125- THROTTLE PEDAL POSITION SENSOR SWITCH E CIRCUIT

All clear except the ABS fault, all return once driven and switched off/wont start.

[marcrbarker]

Very revealing. Many would just cause limp.
If it wasn't that the faults come back each after 'clearing' each time, many those DTCs look like ones get registered during process of troubleshooting (when unplug a connector ie to clean the pins or measure voltage) When DTCs are cleared, are they only erased from the scantool? Though I would expect out of habit you already do another scan just after cleared to make sure gone.
On a MK8 lost comms with ABS would cause a no-start. I don't know if lost comms during running would cause a stop.

[arrolman]

Marc,

I reset a few modules just so I know there's nothing untoward, also checked ABS,BCM and PCM using g forscan and all have no faults. So codes were cleared first then re-checked after just to be sure nothing popped up. They are only showing after van has been driven

[marcrbarker]

Something many have in common is communication CAN bus.
Other codes could be things that were already happening before that hasn't been noticed until now.

[Airthies]

My first thought at seeing that many codes and their description is that it's a battery voltage issue.

Could be either a bad connection, bad battery, earth strap connection at engine to chassis or battery to body(side of seat box).

If it's a poor earth on the engine side it can cause the PCM or BCM to receive voltage spikes or loads.

But I suspect a dodgy connection causing the main power relay to drop out momentarily while driving and not energising when starting due to the codes generated when the power is lost.

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[marcrbarker]

Hasn't low battery voltage got a DTC to say that? OP reported all earths cleaned electrical connections cleaned. Both batteries tested along with alternator all good.
Because there's 5 "lost COMMS" DTCs I would guess there's an intermittent shorting/ broken wire CAN bus, in the steering column / clocks / BCM area

[arrolman]

So quick update, had auto spark ourt, guy knew his stuff, had a quick rummage and came across the aftermarket loom for the old PTO system, starting tracing wiring to dash and came across a lot of spliced in wiring. There was a CANbus aftermarket unit fitted in amongst it which was disconnected and then managed to pull out about 25 wires out leaving only 2 for the fuel pump cutoff. Lots of wires had nicks in them so guessing that may have been part of the problem. Moved into engine bay and he came across another wire for the fuel pump that was fried and looked like had been rubbing against engine block. Put connectors on damaged bits and seems to be working so far , hopefully it's been a combination of old wiring and some aftermarket guff not required. Will keep updated if it goes tits up again

[arrolman]

Cancel last, still f***. Guys coming back on Wednesday to check every wire he said , keep you posted