Grogee's spannering (Maestro, Avensis & Favorit). BIG SPEAKERS FOR TMS LISTENING PLEASURE

[grogee]

I've done some digging around in the relay/battery area of the Skoda to find out where this yellow wire once lived. 

Thought I'd hit the jackpot when I found a bunch of switched live wires soldered together but when I temporarily connected them I've still got the same issue: car starts and runs for about 1 second then immediately dies (with or without throttle). 

In desperation I then connected it to earth in the hope that might make it run but no dice. 

I've no idea what's going on and I'm out of my comfort zone with diagnosing ECU type faults so I'm at a loss on what to try next. 

What I really need is a VW ARC engine specialist who understands the wiring and can tell me where that wire is supposed to go. 

I think next attempt will be to get someone else to turn the key while I look down the throttle body and see if the "fly by wire" throttle butterfly is closing after that 1 second burst. 

Any "mobile electrical specialist" is going to run a mile from a converted Favorit with unknown provenance. 

If anyone has any bright ideas, I'm all ears - at the moment it looks like I've got some quite shiny scrap metal on my driveway. 

Sed worm is sed

[Yoss]

Obviously we've already discussed this a little bit but to no avail. I'm starting to wonder if the yellow wire is a red herring. It may have gone nowhere all along. I've found a few others that do that. 

The bunch of wires coming through the bulkhead on the right I believe are the original Škoda loom as they go to fuse box which looks fairly standard. Then the lot on the left disappearing behind the battery go to the Polo ECU so I assume are VW. And also that mini fuse box is extra. 

Having somebody with you to look down the throttle body is a good idea. Unlike mine which needs a couple of pumps to squirt some petrol down the hole, yours wouldn't start if you had your foot on the throttle. You have to start it without any throttle then give it a bit once it fired. So it could be that it is doing the first bit but the pedal to throttle isn't working. I'm not entirely sure how it works but was something between the pedal and throttle body dislodged when you were working on the heater? 

 

I can't believe I'm saying this but if the worst comes to the absolute worst you should get your money back from a VW ARC engine and set of Team Dynamics Pro Race 1.2s. But obviously let's hope it doesn't come to that. 

[AnnoyingPentium]

If it's electronic throttle, is there a chance the potentiometer in the pedal has given up?

[Yoss]

1 hour ago, AnnoyingPentium said:

If it's electronic throttle, is there a chance the potentiometer in the pedal has given up?

That's why somebody needs to be staring down the throttle body while somebody else pumps the pedal. I was told it was a mk1 Fabia pedal/potentiometer so you might k ow more about how it works than I do.

I never looked at it because I never needed to. So if you pump the pedal with the ignition on but without starting the engine I assume it will still open the throttle. That would be the first thing I would be trying. 

[Missy Charm]

On 31/05/2025 at 18:47, grogee said:

I've done some digging around in the relay/battery area of the Skoda to find out where this yellow wire once lived. 

Thought I'd hit the jackpot when I found a bunch of switched live wires soldered together but when I temporarily connected them I've still got the same issue: car starts and runs for about 1 second then immediately dies (with or without throttle). 

In desperation I then connected it to earth in the hope that might make it run but no dice. 

I've no idea what's going on and I'm out of my comfort zone with diagnosing ECU type faults so I'm at a loss on what to try next. 

What I really need is a VW ARC engine specialist who understands the wiring and can tell me where that wire is supposed to go. 

I think next attempt will be to get someone else to turn the key while I look down the throttle body and see if the "fly by wire" throttle butterfly is closing after that 1 second burst. 

Any "mobile electrical specialist" is going to run a mile from a converted Favorit with unknown provenance. 

If anyone has any bright ideas, I'm all ears - at the moment it looks like I've got some quite shiny scrap metal on my driveway. 

Sed worm is sed

Oops.  Is the car, or ECU, fitted with an immobilizer?  Seems odd that the engine would shut itself off each time, after the same length of time, unless there's something else causing the computer to send a shut-down signal.  

Can't think the throttle would make any difference - even if it wasn't working the car would still tick over; it just wouldn't respond to the pedal. 

[AnnoyingPentium]

15 minutes ago, Yoss said:

I was told it was a mk1 Fabia pedal/potentiometer so you might k ow more about how it works than I do.

There's about four or five different versions of these pedals. All visually identical but not compatible. 

When the throttle pedal on my Mk1 Fabia went, it'd hang onto the revs and would increase and decrease unevenly. I'm not sure it's the cause of the issues here.

Based on @Missy Charm's thread that's just loaded, if it's an immobiliser fitted like the system most VAG cars post about 1998 used, then it'll run for a second then conk out. Have you got another key you can use with it, or something?

Edit - You'll need to have the ECU and instrument cluster flashed (unless it's been adapted) to remove the immobiliser on these.

[Yoss]

It uses a standard Favorit key so no transponder. So using the other key will make no difference. If it has an immobiliser I've no idea how it works. 

[JMotor]

Sounds like Immobilizer to me as well. As they cut signal to the fuel pump. Symptoms are much like when I was figuring out the wiring for my 1800 swapped Corsa B. 

Ones of two way it may have been done to get around it.

Flashed ECU to remove it.

Or...

Hidden is a transponder ring with the chip taped to it. Said chip may have fallen off? Which sounds more likely. Hard to know without being there.

Not sure on what ECU is used with that swap. But worth a look as it being VAG, some egghead has probably worked out how to bin it off.

[Yoss]

6 minutes ago, JMotor said:

Sounds like Immobilizer to me as well. As they cut signal to the fuel pump. Symptoms are much like when I was figuring out the wiring for my 1800 swapped Corsa B. 

Ones of two way it may have been done to get around it.

Flashed ECU to remove it.

Or...

Hidden is a transponder ring with the chip taped to it. Said chip may have fallen off? Which sounds more likely. Hard to know without being there.

Not sure on what ECU is used with that swap. But worth a look as it being VAG, some egghead has probably worked out how to bin it off.

It's the Polo Ecu, but that's a good shout. It could have a chip and ring taped together, that would be the simplest way to by pass it.

It could be a complete coincidence that it happened whilst messing about with the heater but the heater box is exactly half way between the pedal/ignition barrel and the ECU so it seems unlikely. 

In which case it could be something very simple but very hard to find. 

[JMotor]

I'd agree with that.

Something daft will be the cause.

My Corsa is done with the donor car key attached to the ring. 

GM immob is burned in so can't be removed via software.

I had a go at making the patch loom for mine. Got the EML to go off. But could I hell get it to start. Gave up and got a loom made. No difference. 

The hell!? 

Then I did what I should of done in the first place. Check if the fuel pump was getting 12v to it. Discovered it wasn't and it was my fault. Chopped out an old alarm out. Didn't realise it was an immobilizer too! One rejoined wire later. It started. 

Bugger! 😆 

Oooh! @grogee if the pump is easy gotten too. See if the thing is getting all the volts to it. Is the plug to said pump easy accessable @Yoss?

Edit - does the car have an EML of some sort rigged up?

[Yoss]

Yes the pump is easy to get to. There's a hatch in the floor under the back seat and the back seat comes out in seconds. 

And no, definitely no EML, standard Favorit instrument panel. 

[grogee]

Thanks all, I really appreciate the brainstorm. 

@AnnoyingPentium I can rev the engine during that brief second of running - in other words, the throttle pedal and throttle body butterfly valve servo are working. 

This video online said the 'start-run-die' behaviour is classic VAG immobiliser symptom: 

I did what he recommended and connected +ve and - ve terminals together to reset immob - no dice. 

@Yoss you may well be right and the yellow wire might be a red herring. 

My gut feel is that the car has an immob with key reader and chip taped to it, as @JMotor suggests. 

The other part of the story is that I was indeed fiddling about in the dashboard, I removed the glovebox and some other bits to trace the heater wiring and pick up an ignition feed for the radio. 

Under the glovebox there was a black box with some wires in/out of it, I'd assumed alarm or central locking module but might be immob. It's certainly possible I disturbed something when I was rooting around in there. 

Next step will be to check fuel pump voltage and if necessary, bypass it and see if engine runs continuously with a constant 12v feed.

And also to check under glovebox for dislodged bits and bobs. 

I'd be amazed if it's that easy to bypass an ECU that doesn't 'want' to run, but stranger things have happened. 

[Yoss]

This would solve the problem! 

Though you would have to remove the heater box altogether. And probably cost more than the whole car. 

Sorry, not helpful. 

[AnnoyingPentium]

1 hour ago, grogee said:

@AnnoyingPentium I can rev the engine during that brief second of running - in other words, the throttle pedal and throttle body butterfly valve servo are working. 

Yeah, sounds like the immo then as others have said, I'd also be looking for a chip stashed somewhere.

[grogee]

Had another quick play this morning. 

I checked voltage at fuel pump and sure enough it drops to zero after a second or so running, which coincides with the ending dying. 

Next step was to hook up 12v to fuel pump using an old battery and see if I could persuade engine to keep running. 

No dice unfortunately. Pump ran OK (I could hear it swooshing) but engine still died. 

That backs up my theory that ECU cuts not just fuel pump but injectors and/or spark as well. Which would make sense I suppose. 

Next up I'll try and find immob unit, key reader and hopefully the chip as well. 

I suppose I could buy a chip + immob unit which are theoretically paired and plug those in as well. Maybe not that simple - I know Renault link all three (key, steering lock and ECU) which means you can't replace just one. 

[IronStar]

Someone tapped the immo chip to the reader, and it either got dislodged when you were (re)moving things, or a coincidence with the failed sticky tape that was holding it.

If you can't find it or the chip is gone, get it flashed out. Bodging a repair and putting another immo in is a recipe for having this all over again when it gets dislodged again, possibly in the middle of nowhere.

[grogee]

5 minutes ago, IronStar said:

Someone tapped the immo chip to the reader, and it either got dislodged when you were (re)moving things, or a coincidence with the failed sticky tape that was holding it.

If you can't find it or the chip is gone, get it flashed out. Bodging a repair and putting another immo in is a recipe for having this all over again when it gets dislodged again, possibly in the middle of nowhere.

Get it flashed out by whom? 

Note: the car has no OBD2 port... 

[IronStar]

6 minutes ago, grogee said:

Get it flashed out by whom? 

Note: the car has no OBD2 port... 

Car locksmiths offer such services here on the side if you ask them nicely. Possibly the same there? Plenty of 50 quid and below results on Google as well.

It's doable as DIY if you have the tools and are feeling adventurous. Being VW car, googling (or ChatGPTing) ECU model immo off gets all the info.

You can do the ECU flash on the table, and depending on the ECU model, it may need to be done on the table anyway because it's EEPROM flash.

[grogee]

Maestro is obviously jealous of the Skoda, and has developed a new, fun* way of pissing me off. 

Basically it starts, generally dies, starts again, runs, dies, starts and runs OK... But then randomly died 20mins into my journey. Key off - key on, starts fine like nothing happened, got home without another stumble. 

Definitely electrical of some description, but fuck knows what's going wrong. 

It's got its MoT tomorrow so it had better buck its ideas up. I've run out of driveway space for broken cars. 

[AnnoyingPentium]

9 minutes ago, grogee said:

Maestro is obviously jealous of the Skoda, and has developed a new, fun* way of pissing me off. 

Maestro is standing in solidarity with its more communist brethren. Something something ghost of Red Robbo...

[Yoss]

17 minutes ago, grogee said:

Maestro is obviously jealous of the Skoda, and has developed a new, fun* way of pissing me off. 

Basically it starts, generally dies, starts again, runs, dies, starts and runs OK... But then randomly died 20mins into my journey. Key off - key on, starts fine like nothing happened, got home without another stumble. 

Definitely electrical of some description, but fuck knows what's going wrong. 

It's got its MoT tomorrow so it had better buck its ideas up. I've run out of driveway space for broken cars. 

When you took the Škoda off me I said it would be interesting to compare the two but I wasn't expecting to compare the random electrical problems. 

 

[Snipes]

I know it's irrelevant util you sort the running issue but last page you asked about toe and a tendency to wander. In theory toe in should settle it down but if it's running to much toe-in that can also cause odd behaviour so best to get it measured and see what it's doing. 

Tyres can also cause odd steering issues.

[grogee]

LIVE MoT! 

I used to drop my cars with the friendly tester in my old town but now I'm in the big* bad environs of Northampton, I've been recommended this place. 

I just made friends with the tester so that's a good start. 

[grogee]

It's under the microscope now. 

Absolutely nail biting stuff. 

I'm going to phone my mum. 

[grogee]

Forgot to mention, while pre-mot testing the lights and wipers, I managed to headbutt the door frame which gave me a nice forehead scar. Bloody idiot. 

I blame this god forsaken man flu I'm suffering with at the moment. 

[grogee]

It passed. Another year of fun! 

I celebrated by going to Sainsbury's and filling up with E5 £1.42 per litre, the robbing bastards. 

[grogee]

Skoda investigating. 

Pulled out the glovebox to see if it was indeed the immobiliser I'd spotted while faffing away earlier to find a switched +12v for the stereo. 

Indeed it was, tucked behind the dash held on by self tappers.

Initially I began testing the wires to find a feed for the spoof immobiliser signal box I've got ordered. But had a head scratching moment when I couldn't find an earth for it... WTF? 

Then found the smoking gun! An earth ring terminal floating around in mid air, not attached to anything. When I'd reattached the dash last time, I didn't hook this into the dashboard mounting screw. 

For proof of concept I hooked it directly to battery -ve then started the car... IT LIVES!!! 

I didn't like the original earth point which showed too much resistance to ground in my opinion, so I tapped another one off the cigarette lighter and attached it to the original earth ring terminal. 

I just need to re-heat shrink some of the wiring I'd been testing last week, then we're back to normal. Works can continue, eg stereo improvements and engine steady. 

[Matty]

Excellent 👍

[IronStar]

I love how it’s not just an immobilizer chip but a whole bloody key! 😆

Great work on sorting it out!

[Cookiesouwest]

I'm so glad you found the problem and got it going again.