I'm getting a click from ECU relay when ignition on and the fuel pump hums when cranking so from what you say, the ECU must have power. Thanks, at least I can cross that off the list.
the k-line stereo issue is only for MK4 era cars, as they have a k-line to the radio plug which is used on aftermarket stereo by IIRC amp power. MK3 and older dont have any k-line wiring to the stereo plug so nothing to worry about there.# does seem to be an issue with the ecu then, hopefully the new ECU will confirm this. if you haven't got a complete set of immo/ecu/chip then you'll need to code the old immo box to the new ecu with vagcom, not hard but does need to be a registered copy. even if the ecu isnt coded the car should start and run breifly, plus you'll be able to scan ecu with vagcom still. if you need a wiring diagram theres one in my signature link, g3aggadyecu.pdf
Not on MK3s? Thanks rubjonny, that's undoubtedly saved me a few hours scowling at radio wires to no avail. I too, even on my slim knowledge am of the opinion that the issue is with the ECU, and replacement on its way will hopefully confirm. My worry on that however is that when connected, whatever it was that fried the old one will immediately fry the replacement as well. Guess I'll find out when it's fitted. Thanks for the wiring diagram, it's a big help, along with your advice, as said, it's appreciated.
yeah the mk3 has no diagnostics wiring to the radio as they had no capability for it. before the new ecu gets plugged in a good check over of the harness is a good plan, look for any chafed areas. the main earth for the engine loom is under the battery tray so get that looked at and buff up shiny if corroded
Spruced up the earths as advised before plugging in the replacement ECU. The car fired up (albeit for only a second or two until the immo kicked in). Guess I need a recode to be 100% but considering it was dead in the water up until today, I am well chuffed! Thanks very much for all contributions, it was/is thoroughly appreciated. MK3 GTI back on road, I'm going to be smiling like a cheshire cat all weekend. Thanks again!
good stuff, if you clear all the codes on ecu and immob then scan both again see what comes back. ecu will flag immo code if thats the issue and immo box will tell you why
'Engine start blocked by immobiliser P1570' What do you reckon the best option is; getting the new ECU coded or having the old ECU repaired and having the new one for backup/testing?
I'll certainly do that when I get to the car tomorrow (it's at a garage miles away). Not querying your exceptional knowledge and experience obviously but isn't the immobiliser kicking in because the new ECU isn't yet coded for the car?
ah yes, if you put a new ecu on then that would be it I took your post above to mean you cleaned the earths up before trying the new ecu, not cleaning the earths then plugging in the new ECU so yeah, just have to connect to the immobiliser with registered vagcom and perform the ecu coding procedure, dead easy
Does anyone know of a mobile auto electrician, Leeds area, that can recode a MK3 GTI ECU? Turns out the garage where my car is can't get the pin codes, a guy that sometimes does that sort of work for them says he doesn't do ECUs of that age, another says he can do it but the car has to come to him (bit of a catch 22 unfortunately) and the mobile guys advertising are talking silly money even before they've turned up and plugged in. Sent my broken ECU away to be fixed and the company are now saying as it's an unusual case, they need to keep it a further few days (it's a bog standard ECU from a MK3 Golf FFS not something cannibalised from a derelict alien spaceship). No doubt that's a sales ruse to rack up the repair price they'll quote. Anyway, I reckon my best options now are getting the donor ECU I have coded for my car or simply getting it de-immobilsed. Any opinions please as I'm a bit bewildered as to how a straight forward broken ECU job has started to grow so many arms and legs.
I used an immobiliser emulator for a while on my caddy when I had that, used an old immo box and soldered the circuit board inside in place of the original, then it just plugs straight in to where other was. I'll see if can find info
https://www.ebay.co.uk/itm/192509127827 This also shows where to connect, has mk3 box pictured in photos.
Ah yes, I was looking at things similar but was a bit sceptical (£20 - £30 ones I was looking at on ebay have now all been completely removed for some reason?). Thanks for that, I'll pencil that back in as a reserve.
you dont need a pin code for this, its a case of log into immo box, click a couple buttons and you're done. you only need the SKC code if you want to code chips to the immobiliser box, but you already have a matched chip and box so you're all good that side of things. so all you need is someone with a registered copy of vagcom, and even if they dont know how we can tell them
I've read this procedure from a RossTech page _____________________________ ECM Matching Prerequisites: Battery voltage at least 12.5 V. Immobilizer II ECM [Select] [25 Immobilizer] [Adaption - 10] Leave channel at "00" [Read] [Save] [Done, Go Back] [Close Controller, Go Back - 06] [Exit] Turn ignition OFF for 15 seconds. Start vehicle. __________________________________________ Here's what I'm looking at for the immo and ECU when a registered VCDS_Lite is attached (note the 'Advanced Functions' not greyed out). Is it as simple as following the RossTech above? It can't be as simple as that, surely? I don't want to crackle the newly acquire ECU somehow as the I'll be back to square 1.
