Glowplugs and DSG's

[antony.charnley]

Quick question for the master tech and guru: no guessing, please.

Is there any conceivable relationship between an implausible glow plug three error, a DSG shifting lag, and an occasional delay transmission shunt from a 2016 Bluemotion tech 150? It feels like there COULD be a shift relay in the DSG dragging. Maybe.

The box was rebuilt, and there was a new DMFW, DS drive shaft, and glow plugs (although they have since faulted again); compatibility or connector error, perhaps? But reporting an Electrical error & Implausible signal as per the below scan.

I went back to the transmission place this morning for diagnostics, but they think the Glow Plug issue could be causing the shift timing/smoothness inconsistencies. Explaining that glow plugs do more to balance the engine since 3 reads pressure. I've told him until the plugs are replaced and fault-free (next Tuesday). Then, I can see how it behaves over Christmas and take a proper look at the new year.

The transmission work was completed with AP Transmissions/Midland Transmissions in Kettering; they said they tested the relay operation during the rebuild, and it is unlikely to be that. They do have a DSG Skoda in right now with the same messages I'm getting regarding glow plugs, and they think it's linked to the shifting issues that the Skoda is also demonstrating.

 

[n10n]

I thought they only glowed up started the engine, but I guess hes right if 3 is a pressure reading it as it is on mine.

Glow plugs do stay on after engine start until water is about 50°C. Also plug #3 indeed measures pressure.

VW T6 Custom PID codes for DPF

Averaging RPM x time => number of strokes Averaging injection quantity x strokes => fuel amount in grams Just have been using average diesel density 830 g/l to get litres. I do recognize this possibly could be improved... but also density of diesel varies (e.g. summer/winter). Also the injection...

www.t6forum.com

 

[antony.charnley]

Glow plugs do stay on after engine start until water is about 50°C. Also plug #3 indeed measures pressure.

VW T6 Custom PID codes for DPF

Averaging RPM x time => number of strokes Averaging injection quantity x strokes => fuel amount in grams Just have been using average diesel density 830 g/l to get litres. I do recognize this possibly could be improved... but also density of diesel varies (e.g. summer/winter). Also the injection...

www.t6forum.com

Thanks, it's a helpful starting point and potentially links issues better to cold starting. Mitigating the thoughts of gearbox mechatronics or DSG oil temperatures slowing things down to show more when cold.

Also, it is worth noting that the above DSG delay and smoothness clunking issues are part of the symptoms that led to the transmission investigations and booking of the DMFW replacement. In the week or so after that prognosis, the starts were getting trickier, clunkier, and the tick-over shakier, everything you expect from a clapped DMFW. But that was the first time I got the glowplug messages while waiting to put it in for transmission work. Maybe the DMFW had shaken a glowplug lead off or towards a broken or intermittent connection. Now they have replaced them all, and the fault is back; perhaps my theory was correct, and the £100 lead replacement is next; this is the Christmas gift that keeps on taking. More information after Tuesday's lead test and 2nd set of plugs then. My local Indy is great, but they are not excited about returning to what was charged as a 4-hour job and presumably will be the same again for them - not my bill this one, I'm assured.. maybe..

 

[n10n]

Maybe the DMFW had shaken a glowplug lead off or towards a broken or intermittent connection.

Sounds plausible.

Your error codes are related to pressure sensing specifically, not the glow system. Looking at the wiring diagram pressure sender G679 connects directly to the ECU J623 (and ground, brown wire) - hence I think the glow plug module J179 can be ruled out.

The ground wire connects to a shared ground in wiring harness and eventually to "Earth point 4, engine prewiring harness", whatever that may be. But the point is that there's lot of other stuff grounded through the same ground point so you should have more DTC's if the actual earth point was cut. Therefore I would look into the green and black wires to the #3 plug and just test brown continuity to the chassis with a multimeter, shouldn't have to chase brown all the way to the earth point even if there's no continuity.