T6 won't start after flat battery (Solved)

[Victor500]

Hi guys, I've had a nightmare of a weekend with my T6 - yesterday due to the storm my back window was smashed by flying debris, so I wrapped the van up in a tarp and waited for the winds to die down. This morning when I went to move the van it appears that my tarp got stuck in the tailgate and so the tailgate has been 'open' all night, causing the interior lights to drain the battery.

When I tried to start it the first time, it turned over but struggled and didn't start. Despite connecting jump leads (and seeing over 14v measuring across the battery) it now won't start at all - it's just nothing when I try to turn it over, the only change being a flashing coil light on the dashboard.

I've done some internet research, so these are the things I've tried (with no change to the symptoms)

• Checked fuse SC23 (Starter Relays) - couldn't get the fuse out but it looks ok (how are you supposed to get these fuses out that are right at the bottom of the fuse board!?)
• Checked fuse SC56 (BCU Starter Feed) - fuse looked ok, swapped fuse just in case.
• Used jump lead to earth battery to gearbox, in case of ground issue.

My VCDS scan is showing the following fault, with todays date, the timestamp being when I first tried to start it this morning (when it turned over but didn't catch)

5456 - Starter Will Not Turn
P3054 00 [101] - Jammed or Electrical Malfunction
Not Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Status: 00000001
Fault Priority: 2
Fault Frequency: 1
Mileage: 277512 km
Date: 2022.01.30
Time: 11:08:19

Does anyone have any suggestions what to try next? I'm assuming its an issue with the starter motor (or power/signal to the starter motor). Is it likely just a coincidence that this has occured when the battery went flat, or am I missing something obvious?

With the fact the van has no rear window and therefore isn't secure, I'm not particularly wanting to get it recovered to a garage at the moment.

Cheers for reading.

John

 

[Howzat]

Charge battery overnight and if that fails try earthing the starter with those jump leads as mentioned in this post.

 

[Victor500]

Hi Howzat, thanks for your reply.

Update on this evenings "progress". Unfortunately none of these actions had any effect.

• I had the battery on charge overnight, and reconnected it to the van this evening but no change to the symptoms.
• Swapped in the battery from my car and that made no difference either.
• Earthed the starter from the bottom bolt to the gearbox using the jump lead

One thing that is puzzling me, is that I don't seem to be getting any voltage when checked the cable from the battery at the point that it attaches to the starter motor. My understanding (and I may well be wrong!) is that this cable should be permanently live when the battery is connected?

My understanding is that the issue has to be caused by one of the following:

1. Poor earth (have tried earthing starter bolt to gearbox)
2. No signal/voltage in the trigger cable from the ignition switch (for which I imagine there could be numerous causes beyond fuses 23 and 56 that I've checked already)
3. No voltage from the battery (if the cable is knackered - is this even feasible? It's a pretty thick cable but I was struggling to measure any voltage on it this evening)
4. The starter itself is knackered

I'm going to keep plugging away, but any input/thoughts from forum members would be very much appreciated!

Cheers,

John

 

[Dellmassive]

have a look at:

J906 & J907 - Starter relay 1&2, in E-box in engine compartment

which is ECM control signal for the starter solinoid.



they feed the start motor trigger solenoid.

The startermotor is shown to have a perm gound

and a direct battery connection at the battery post terminal.





...


the alternator feeds the SA fuse box - under the starter battery. - which then feeds the battery at the POS terminal.


++++


so check the battery has two main fat power cables connected.

 

[Victor500]

Thanks for that Dellmassive - it'll be Wednesday before I can take a look, but I'll let you know how I get on. Cheers, John

 

[Dellmassive]

i had a similar issue on my T5.1 6mnths after being in VW for a new engine . .


long story short they didn't tighten the main pos feed at the starter . . . . so after a while it corroded and made a poor connection - causing the problem.

i had the same codes - starter will not turn etc.


in my case i had to remove, clean and refit the start motor main battery connection.

 

[Dellmassive]

post some pics for us all to see. . .

the battery and its connections . .


and the starter motor connections if you can.

 

[Victor500]

Hi Dellmassive, here are photos:





It's all quite corrode and horrible isn't it!? - perhaps the next step is to try to clean this off as best as I can.

 

[Victor500]

When trying to check the voltage at the nut circled below (which I believe clamps the battery cable to the starter solenoid?) I couldn’t get anything about about 0.2v

 

[Dellmassive]

those are the two main feeds - one should be the starter.

id cut back the heat shrink and check the cable for corrosion.



.
this is the bolt that was loose/corroded on mine. (yellow)

the plastic shroud (green) is there to protect the connection, but can be removed.

that bolts to the solenoid. - it has an L shape crimp on the end so it sits on the





on this example:

yellow is the main battery feed.

and red is the output side of the solinoid to the motor windings.





the other wire is the trigger feed from the starter inhibit relays . .

 

[Dellmassive]

id be checking the main power connection at the battery and at the start motor - fat black cable.

also the main engine earth strap.

your metal work and cables seem very corroded.

i may just need a good clean up . . .

+++++

remove battery,
remove main battery POS cable - wire brush + emery cloth to clean
remove main battery NEG cable - wire brush + emery cloth to clean
Remove main starter feed cable - wire brush + emery cloth to clean
reconnect and test (main battery NEG last)

++++++++

another test -
Remove main starter feed cable - wire brush + emery cloth to clean

++++++++

another test -

remove battery,
remove main starter feed cable,
use multimeter to test resistance of cable
should be very low ohms.

+++++++++

i the cable is good . . .

you should see battery voltage at that bolt on the starter motor.


+++++++++

 

[Victor500]

Bit of an update on progress so far…..

Managed to clean up the connector from the battery to the starter, and tested showing 12v, so I was happy that the battery cable isn’t the cause. I’ve ordered (and received) a new battery cable so I’ll fit that anyway as the old one was badly corroded even if still functional.

Found a fella selling a second hand starter motor near my work so went to collect that on Tuesday night (bit of a gamble I suppose but only £20). It came with the solenoid wire attached, which gave me everything I needed to swap parts in a logical process of elimination.

Removing the solenoid wire from the starter in situ is a bit fiddly, so I modified the connector that came with the ‘new‘ starter so it would slide off easily.



Once I‘d done that, I bench tested the ‘new’ starter, which seems to be working fine. I then used the modified connector, a jump lead and a short crocodile clip cable to test the original starter. At this point I was hoping the original starter wouldn’t turn over, as I was a bit nervous of a more complicated electrical fault with the ignition circuit. Thankfully, the old starter failed to fire. All that left was to use the original wiring to connect the ’new’ starter (resting precariously on the subframe ) and turn the key. I was very pleased to hear the starter motor whirring away.

Now that I’m happy with the diagnosis of a knackered starter motor, I just need to swap in the ‘new’ one. The top bolt looks an absolute pain to get to, so figuring out how will be tomorrow‘s mission!

cheers,

John

 

[Victor500]

I’m not sure whether to change the title of this thread, if possible, as it turns out the flat battery wasn’t anything to do with th3 problem. Just bad luck with the timing!

 

[Lukefx]

Hi @Victor500 , I have exactly the same problem and after checking fuses, earth etc have put it down to the starter motor and more searching found this post.
The mechanic I use is booked up so I'm going to check all the connections etc but @Dellmassive 's comments here are quite coincidental , in a sense that mine had a new engine 7 months ago. I'm going to check all the connections over the weekend and see if anything is obviously wrong.

"i had a similar issue on my T5.1 6mnths after being in VW for a new engine . .


long story short they didn't tighten the main pos feed at the starter . . . . so after a while it corroded and made a poor connection - causing the problem.

i had the same codes - starter will not turn etc.


in my case i had to remove, clean and refit the start motor main battery connection."