AAN starting issue

[marius555]

Hello to all,

I have some issue starting the car. As i checked everything possible i have noticed that on fuse #15 i dont have +12v and the instrument cluster is dead.

Also when i turn the key to start , the engine engages but i don't have no spark on the coils and the fuel pomp isn't working .

I managed starting the car in two ways:
1: Conecting fuse #15 ( in the fuse panel ) with fuse # 8
2: Connecting pin nr. 27 from ECU directly to the battery



Please advise what to do next ?

[UrS4boy]

What you are doing is dangerous and can lead to electrical fires. As I pointed out in the reply to your PM, you need to check the fuse in the yellow holder above the ECU.

However, because there is also an issue with the instrument cluster, I have to assume that your ignition switch has failed. Replace it ASAP, using a dealer supplied switch (not aftermarket), using this DIY procedure (below) and then report back:

http://12v.org/urs/IgnitionSwitchReplacementDIY.pdf

[marius555]

Yes , indeed , the first thing i've done was to replace the ignition switch.

I still don't have +12V on the bk/green wire on the #27 on the ECU . Also , if i put a strap on fuse #15 with #8 the car starts.

Also i have opened the Fuel Pomp Relay and nothing there ...

I will attach the pictures right away.


What to check next ?!

[UrS4boy]

Yes , indeed , the first thing i've done was to replace the ignition switch. I still don't have +12V on the bk/green wire on the #27 on the ECU . Also , if i put a strap on fuse #15 with #8 the car starts.

With the ignition key turned to "RUN" (not start), check to see if you have 12V on the black wire input side to the yellow fuse holder (the one that the green/blk wire come out of). The Jumper trick between 15 and 8 seems either to be a red herring OR it is a way around an immobilizer issue. What is the PN on your ECU?

http://forums.quattroworld.com/s4s6/msgs/137287.phtml

[marius555]

Indeed , i don't have +12v on the bk wire from the yellow fuse ....

Also, i have tried to start the car only with the ignition switch. The car started for 2 seconds and it stopped and the immobilizer display was blinking. After that i've connected the ignition switch into the key holder and the limmobilizer went off.

The ECU p/n : 4A0 907 551 C

[UrS4boy]

Indeed , i don't have +12v on the bk wire from the yellow fuse .... Also, i have tried to start the car only with the ignition switch. The car started for 2 seconds and it stopped and the immobilizer display was blinking. After that i've connected the ignition switch into the key holder and the limmobilizer went off. The ECU p/n : 4A0 907 551 C

All of the NAmerican UrS cars used the 4A0907551AA, a non-immobilizer, standard transmission, Motronic ECU. The 551C ECU is an immobilzer ECU for standard tranmissions. 551D is an immobilizer ECU for AANs with automatic transmissions. The immobilizer is in two parts:

1. a reader ring for the key, at the end of the ignition switch
2. programming inside the ECU that waits for the signal from the reader ring. No signal = no start.

An immobilizer ECU *can* be reprogrammed to be a non-immobilizer ECU .

I suspect that you have a problem with the immobilizer part of the ignition switch assembly. If I remember correctly, there is a ring at the end of the switch with a wire (that goes to the ECU). (Can't find photos that I thought I had)

[marius555]

Why i don't have +12V on the yellow fuse ?

There is a cable with two small wires from the ignition shaft to this 4A0953234.
Can this part cause all these problems ?


Many thanks for your support,
Marius

[UrS4boy]

Why i don't have +12V on the yellow fuse ? There is a cable with two small wires from the ignition shaft to this 4A0953234. Can this part cause all these problems ? Many thanks for your support, Marius

4A0953234 = "control module for anti-theft device", i.e. the immobilizer. If it doesn't work, the ECU doesn't get powered = no 12V to the ECU via the black wire on the Yellow fuse holder. (I presume)

4A0953234 was superceded to 8D0953234 as of 31/05/1995.

I think the issue is the ignition portion of the immobilizer system, i.e. the reader that tells the immobilizer it is a legitimate key. Sorry I can't find photos of what I am talking about.

[prj]

4A0953234 = "control module for anti-theft device", i.e. the immobilizer. If it doesn't work, the ECU doesn't get powered = no 12V to the ECU via the black wire on the Yellow fuse holder. (I presume)

No.

ECU is powered all the time and ECU tells immo what to do and decides everything.
It's all in software.

Only thing that box does is reads the keys matched to it and intercepts comms to ECU at some stages (and communicates). It's a pretty dumb box.

[UrS4boy]

No. ECU is powered all the time and ECU tells immo what to do and decides everything. It's all in software. Only thing that box does is reads the keys matched to it and intercepts comms to ECU at some stages (and communicates). It's a pretty dumb box.

Not wanting to start a debate but Marius is not getting switched power to the ECU (yes, the C4 UrS ECU is powered all the time through the red fuse holder) but there is still switched power to the ECU (via pin T55/27) and the ignition coils via the yellow fuse holder.

What are your thoughts on why he can start the engine by jumping fuses 8 and 15 but no way else?

http://forums.quattroworld.com/s4s6/msgs/137287.phtml

[prj]

Not wanting to start a debate but Marius is not getting switched power to the ECU (yes, the C4 UrS ECU is powered all the time through the red fuse holder) but there is still switched power to the ECU (via pin T55/27) and the ignition coils via the yellow fuse holder.

What are your thoughts on why he can start the engine by jumping fuses 8 and 15 but no way else?

No time to look.
But when engine start is blocked by immo and immo light is flashing you can connect to the ECU perfectly fine and run diagnostics on it, so that's not the problem.

I had an UrS6 with immo fitted.
In fact, you can remove the immo unit altogether, just unplug the plug, bridge the K-Line, re-write ECU software and throw the box in the dump. Everything will work fine.

These are facts.

Probably his wiring is damaged or the thermo fuse (if that's on IGN, I don't remember).

[UrS4boy]

No time to look.

But time to criticize and suggest all problems can be solved by *just* reprogramming the ECU.

So you don't know why bridging Fuses 8 and 15 bypasses the immobilizer. I am shocked.

[pasbogdan]

It is not immo(from my experience).All immo related things stops the car after a fiew seconds.An immo ecu in a non immo car starts engine and stops it in a fiew seconds.This car does not start.It does not get 12v on pin 27(that pin should get 12v with ignition on)
If i were Marius i will follow wire to the 12v source.

[UrS4boy]

It is not immo(from my experience).All immo related things stops the car after a fiew seconds.An immo ecu in a non immo car starts engine and stops it in a fiew seconds.This car does not start.It does not get 12v on pin 27(that pin should get 12v with ignition on) If i were Marius i will follow wire to the 12v source.

I agree about needing 12V at Pin 27 (via the yellow UrS6 S115 fuse holder). He isn't even getting power to the input side of the fuse holder. Hence my thoughts (right or wrong) about the ignition switch and maybe the immobilizer key reader ring.

What is perhaps more troubling is the trick he is using, i.e. jumping Fuse 8 and 15, to get the car to start.

Fuse 8 = Luggage compartment light, footwell light, left, footwell light, right. (so a non-switched source of power) (Should be 15 amp, NOT 25 amp)

Fuse 15 = Instrument cluster, mirror adjustment switch. (Probably switched but how does this back flow current to the ECU?) (Should be 5 amp NOT 25 amp)

[prj]

But time to criticize and suggest all problems can be solved by *just* reprogramming the ECU.

So you don't know why bridging Fuses 8 and 15 bypasses the immobilizer. I am shocked.

No time to look because I have a flight to catch in 7 hours.

I did not suggest this can be solved by reprogramming the ECU, because in this case the immo has nothing to do with the car not starting. There is no power on Pin 27 so ECU never gets the "turn on" signal, and immo does not affect it, because as I said, you can unplug the immo completely from the system, leave the connector hanging, reprogram the ECU and have the car start. This means the 12V to ecu does not go through immo, good enough for me to suggest that on this car the immo has nothing to do with the not starting problem, but rather that it is a wiring issue or ignition switch.

I don't have time to look at the diagrams now, will look later if it will still be important then.

Your post was uncalled for. You don't have to be an *** about it. Just leave the immo out of this, it is not the culprit here, it is also not getting bypassed, it blinks because it can't communicate to ecu or can't read the key transponder. Immo light off = immo happy.