Trouble starting possible ACU ???

R

richy1009

Member
United-Kingdom
My Audi A2 1.4 TDI SE 2005 has problems starting on hot days after being in the sun, even starting for the first start of the day with a cold engine.
It fires but dies instantly . After several attempts it starts. The car has a new battery and when it run it has no problems.
I noticed during the problems starting that the glow plug pre heater warning light was flashing along with the immobiliser warning light. On cooler days below 22deg it starts ok.

I am suspecting a possible ACU problem or maybe dodgey contact !!
Has anyone experienced similar problems..
Thank you all
 

Howey said:
Sounds like the immo reader playing up
Click to expand...
I agree. Dodgy comms between the car and the immo chip. See if it's any difference with second key, (hope you've got one). Also, resync the fob to the car. (Instructions were posted on here a few days ago).
That communication does not rely on the fob battery. Bit like contactless card payment, the signal from the car "reads" the little glass phial thingey in the fob.
Mac.
 
Thanks Mac for your help
I have a second key but it stopped working a couple of years ago , i just tried it again and it comes with the same error indication as i am now getting intermittently on my other key( pre heater warning light was flashing along with the immobiliser warning light.) . Does this indicate an intermittent fault on my Fob or the car reading the immo chip. I think i really need to get the second key sorted ! i have tried replacing the battery. any pointers to how to get the second key sorted.? I fear that the problem could go hard !!!!!!
 
richy1009 said:
Thanks Mac for your help
I have a second key but it stopped working a couple of years ago , i just tried it again and it comes with the same error indication as i am now getting intermittently on my other key( pre heater warning light was flashing along with the immobiliser warning light.) . Does this indicate an intermittent fault on my Fob or the car reading the immo chip. I think i really need to get the second key sorted ! i have tried replacing the battery. any pointers to how to get the second key sorted.? I fear that the problem could go hard !!!!!!
Click to expand...
I think you should try re-syncing both keys.
There was a how to very recently, but I can't find it.
Best I can do is this from long ago:
Put key into ignition
Turn to ignition (don't start car)
Turn key off and remove from ignition, then, immediately press unlock on remote fob.
I'm sure someone will post it again, but try as above.
Mac.
 
Thanks again for that Mac
I have already done the re syncing i did what you said , following a procedure on you tube. now my spare key will unlock and wind the windows down but will not start the car , the immobiliser light stays on. The other key is working fine but seems to give problems when the car has been left in the hot sun !!
 
I think that ultimately, it's probably the CCU being affected by the heat.
Mac.
Edit: Typo, should be ECU, not CCU 😚.
Mac.
 
Last edited:
Immo is nothing to do with the remote locking or CCCU.

The chip reader on the barrel isn't reading the key maybe worth checking nothing is fouling the reader or get the immo removed from the ecu
 
Thanks Howey for your input .. one key works fine ( when its not too hot) but the spare will only unlock the car but not start it. Do you still think problems with the immo reader ? .. i assume that reader is located in the steering column where the key is inserted . is that correct ?
 
Strange that heat effects the operation
Yes it's on the side of the barrel
Best option if it was my car would be to get a "surf" third key (around £10 with blade cut from photo on ebay) then fit a new chip to that key, and the non working key and recode all 3 keys (keys have to be coded all together)
This way if the working key still plays up you could then swop the chip from the 3rd "surf" key into the remote key
 
Howey said:
Immo is nothing to do with the remote locking or CCCU.

The chip reader on the barrel isn't reading the key maybe worth checking nothing is fouling the reader or get the immo removed from the ecu
Click to expand...
Is the immo chip reader in the door?
I thought it was in the instrument cluster, and communicated with the ECU.
Apologies if I've got that wrong.
Where ever it is, I think the car end of the fob to car syncing is being affected by the heat, not the fob chip , which is dumb. Just my opinion.
Mac.
 
PlasticMac said:
Is the immo chip reader in the door?
I thought it was in the instrument cluster, and communicated with the ECU.
Apologies if I've got that wrong.
Where ever it is, I think the car end of the fob to car syncing is being affected by the heat, not the fob chip , which is dumb. Just my opinion.
Mac.
Click to expand...
The whole immobiliser function is completely separate from the remote lock/unlock functionality.
A scan might give a clue here. If, as seems likely. it's the immobiliser function at fault, the scan will show this.
The cluster interrogates the RFID chip in the fob, and if the response is correct, the cluster enables the ECU to run the engine. The immo symbol in the DIS means this process has failed. The fob chip is like your credit card, energised by the reader, (the dash cluster).
Mac.
 
Suggest you take a look at the ECU itself, in the underfloor compartment, passenger side.
Just to check all is well, and dry.
Remove plastic trim on the bottom of the door frame, then lift carpet. You'll see the cover, and the fixings. Probably not the cause, but easy to rule out.
Mac
 
i have checked the ECU reseated connectors and have got my spare key sorted now . It is all working now just have to leave it under the hot sun and see what happens. I was thinking to go over the ignition key slot with a hair dryer and also maybe the ECU and see if i can make it fail to pinpoint the failing area. would that be advisable ??
 
richy1009 said:
i have checked the ECU reseated connectors and have got my spare key sorted now . It is all working now just have to leave it under the hot sun and see what happens. I was thinking to go over the ignition key slot with a hair dryer and also maybe the ECU and see if i can make it fail to pinpoint the failing area. would that be advisable ??
Click to expand...
I wouldn't try that, it's too easy to damage aged parts. The ECU, or the cluster, is the problem is my guess. I was thinking of putting a piece of aluminium foil, (or the stuff you put behind radiators), shiny side up, on the dash, above the cluster, to keep it a bit less hot by reflecting the sun.
When you feel brave, maybe get the cluster out and check/clean the connectors.
🤞Mac.
 
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