Strange issues with Greenline 2. High idle with brake pedal pressed, flashing glowplug lamp, unknow DTC in the Engine ECU

[lowedb]

I've had a bit of a search of the forum and can't find anything quite the same as this issue. It's my Mum's car.

 

It did get a bit of a low battery during Lockdown V1, but never got low enough to damage the battery, so after recharging it started and ran fine. Gave it a good run and parked it up. Later, while still enough charge in the battery started it and brought it to my house so I can stick a small charger on it to maintain the battery. Been doing that for a number of weeks now.

 

Needed to take my Dad for his Covid jab this morning, and it started and ran fine to take him there. On the way back, again was fine for most of the way, but then I noticed that when I stopped at a junction, the idle speed was very high (1500) and I haven't found anything on here matching that. Also at that point the glowplug lamp started flashing. My initial thought was that it was trying to do a regen and not managing. I thought a decent run on the way back would fix it, but when I got back in after dropping him off the glowplug light stayed off. However the high idle persisted, though not every time. It seems to drive fine, though I don't know the car well. Can't feel any change in performance from any other time I drove it though.

 

I wondered if it might be developing sticky throttle pedal, having had this on our own Skoda of the same era some time ago. I planned to knock the throttle to see if it 'unstuck' but as soon as I took my foot off the brake pedal, Idle dropped very quickly to normal. This was completely consistent, the instant the brake pedal was released idle became normal. Didn't have any glowplug lamp activations this time. The high idle was also always exactly 1500 RPM, a bit too consistent for a sticky throttle pedal

 

I scanned the car with VCDS, and only one fault code. In the engine, but VCDS list this as an unknown fault code, and I am using the current version.

 

My suspicion is the brake light switch, given the change of behaviour when released. But the Engine ECU has no code for a brake pedal switch fault. The ABS ECU to which I believe the switch is connected has no DTCs at all. However looking at the measured values for the switch in the ABS,  I see waht appears to be an oddity. There are two switches in the box. BLS (for the lights themselves) and BTS (for plausibilty checking of BLS) and two measured values corresponding. But while the BLS measured value read as expected, the BTS value was completely blank. The brake lamps themselves are all working fine.

 

I'm aware that earlier cars had significant issues with the brake lamp switch, but is this an issue anyone has seen on a Mk2 (2010)? The symptoms are just a bit odd and specific.

Edited 17 December, 2020 by lowedb
Clarified limp home not active

[m8t]

My 2011 1.6tdi often had a high tickover. Its part of the regen process. Sometimes flashing glow plug too that cleared after a run. I think it flashes when the DPF is over a certain % of particles and needs to burn them off.

I had the following replaced during my ownership, O2 Sensor, EGR valve & exhaust gas temp sensor.  I was glad to get swap for 1.9tdi. I had a slightly sticky accelerator pedal on my 1.9 but cured it with WD40.

Edited 17 December, 2020 by m8t

[lowedb]

7 minutes ago, m8t said:

My 2011 1.6tdi often had a high tickover. Its part of the regen process. Sometimes flashing glow plug too that cleared after a run. I think it flashes when the DPF is over a certain % of particles and needs to burn them off.

I had the following replaced during my ownership, O2 Sensor, EGR valve & exhaust gas temp sensor.  I was glad to get swap for 1.9tdi. I had a slightly sticky accelerator pedal on my 1.9 but cured it with WD40.

Hi and thanks. This is the 1.2 tdi. I've never had one but all of the Skoda tdi's we have had (including a Mk3 1.4 tdi) raised it from around 750 RPM to around 1000. This one is much higher than I've ever experienced on any other at 1500 RPM. Also if it were regen, I'd expect it to persist until regen were finished rather than coming and going during one drive, and when the brakes are released. It does have a seperate DPF warning light too, and it's only coming on during self test at ignition on. Also no fan running nor hot smell that all of our others have done.

[mrgf]

Is the stop-start function working properly?

[lowedb]

1 minute ago, mrgf said:

Is the stop-start function working properly?

It wasn't when the warning light was flashing, but was working OK after that when the light wasn't flashing.

[mrgf]

Ok, have you re-checked coding? Strangely, codes can be stored for duff batteries, etc, despite being replaced and no code showing... Its like the code is there but-well-coded! Be sure to get any existing codes fully deleted, if possible. I am clutching straws a little here but it really can't hurt to be sure you are starting with a clean sheet.

[lowedb]

2 minutes ago, mrgf said:

Ok, have you re-checked coding? Strangely, codes can be stored for duff batteries, etc, despite being replaced and no code showing... Its like the code is there but-well-coded! Be sure to get any existing codes fully deleted, if possible. I am clutching straws a little here but it really can't hurt to be sure you are starting with a clean sheet.

Hi. No not checked coding, but I don't have a record of what the coding would have been.

 

But maybe you mean checking for fault codes? I checked twice, both times the same one, but then I haven't cleared it. The car is going to the main dealers anyway (MOT and service) so want to leave any fault codes in there in case it helps them (though I suspect it won't). Not my car, not my decision......