Turn key...nothing but dash lights

[Proph3t]

Hi guys, This is an issue I have had a few times over the past weeks in my 96 A8Q 4.2, 4speed tiptronic, but its ALWAYS worked the 2nd, worst 3rd try. I turn the key to accessories just fine, radio, windows, sunroof etc work fine; but when I turn the key to start I get nothing but ignition lights. No noises, no cranking...and worst of all no start :/ Knowing the car has the PARK and NEUTRAL startup lock feature, I usually just cycle the gear lever through NEUTRAL back to PARK, and away it starts perfectly. BUT I had noticed a few times I didnt even have to do that, I'd just turn the key back then to start again and it would be fine...leading me to believe it isn't related to the transmission switch, but instead maybe an ignition switch or immobiliser issue. I've tried starting in NEUTRAL as well as PARK, tried holding the lever forward in PARK etc; foot hard on the brake pedal etc etc. I'm using a spare cut key like usual, but I've got the original keys somewhere (just moved house) and would like to try that in case its key related...Are they security chipped at all? I've never used the remote button to lock or unlock that car as its never worked in the 6 years I've owned it, so I just lock and unlock with the key in the door. Either way the car is now dead on the street, and I'm not sure where to begin testing or what to look for. Its way beyond the usually carburettors and distributors I'm familiar with

[Proph3t]

So I tried the original key. Tried locking and unlocking from both passenger and driver door, no start. Dash lights up as usual at pre-start, but just nothing when turned to start.

Noticed that cycling through all the gears shows the correct selection on the LCD screen, so I'd hope that eliminates any sort of gear selector switch, or is this separate to this F125 switch I hear about?

I also noted the flashing hazard switch light on the dash stops, indicating the alarm etc is off, so the key in the door seems to be doing its job.

We did have some flooding around the area last week and my wife was forced to drive very briefly through water, about 30cm deep. But not long enough to be dangerous or hopefully done any damage...but although this is a pre-existing issue, the water way have finished it off. Seems to not be linked though.

Starter motor?
Solendoid?

[tozoM8]

Most likely the ignition switch.

[Proph3t]

Originally Posted by tozoM8

Most likely the ignition switch.

Thanks for the reply.

Being reasonably cheap and easy to change out...this is good news

[Proph3t]

New development.

This morning before work I pulled the starter and fuel pump relays and stripped them down to look for obvious damage or breakage.

They both looked good, but the fuel pump one had a little pitting on 2 of its 3 contacts, similar what you get in distributor points when worn...not sure if its an issue.

Anyway, I put them back into the car, then tried about a dozen times to start it with lots of clicking and snapping from the general relay area, then suddenly it turned over and started perfectly! I let it idle for about 5 minutes but as it warmed up it started to struggle and eventually died. I immediately restarted it without a hassle and it sat for 30seconds, then spluttered and died again. Giving it a bit of throttle didnt seem to help. Also, the security light DIDNT light up on the dash, so it wasnt the immobiliser kicking in.

Since I just moved I cant for the life of me (and the A8) find my VAGCOM dongle so I'm a little stuck for finding error codes etc. And its parked on a busy street making it hard to start stripping the column to probe ignition wires.

This sounds like a fuel starvation issue by the way it acted...possible fuel pump issues. Might try a new relay.

Any ideas?

Thanks in advance.

[Proph3t]

Kind of talking to myself here, but I'll keep a log of whats happening.

Had a mobile mechanic come look at the car, he was able to clear the fault codes, although I wasn't home to see what these codes were, but he said everything looks good except there is "no power to the ECM". I'm not sure exactly what he means by the ECM because if he means ECU, exactly where is he clearing codes from? Aren't these stored in the ECM/ECU?

He said he cant do anything else, but advised if I do get it started to get it to a workshop ASAP.

Useless since it wont start...

Someone else suggested the crank angle sensor, water temp sensor, or ECU relay. Any idea where these are?

Time to buy a Mk1 Golf ...again.

[silverd2]

Originally Posted by Proph3t

Kind of talking to myself here, but I'll keep a log of whats happening.

Had a mobile mechanic come look at the car, he was able to clear the fault codes, although I wasn't home to see what these codes were, but he said everything looks good except there is "no power to the ECM". I'm not sure exactly what he means by the ECM because if he means ECU, exactly where is he clearing codes from? Aren't these stored in the ECM/ECU?

He said he cant do anything else, but advised if I do get it started to get it to a workshop ASAP.

Useless since it wont start...

Someone else suggested the crank angle sensor, water temp sensor, or ECU relay. Any idea where these are?

Time to buy a Mk1 Golf ...again.

You really need to know what codes he read...most codes will stay cleared until the car runs (or ignition on?) for 2 cycles.

The ECM (ECU...same thing) can give codes when it's having a power supply problem...he must have read a code indicating that...don't know the # right off the bat, but there is a code for power supply (relay...inside E box with the ECM...in fresh air plenum...relay position #4).

The engine speed sensor (or crank position sensor, on trans bell housing left side) would also keep an engine from starting or running...like a bad ECM power supply relay.

He should have read a code for either of those , if it was the case.

Coolant temp sensor could cause fuel mixture issues (too lean or rich), but not likely a no-start problem....also a code for lean run issues, if applicable.

[Proph3t]

Thanks for the feedback

I keep reading of the bell housing mounted speed/position sensor, so I'll definitely take a look at this.Need to looking it up in VAGCAT or something to get an idea of what it looks like.

I really wished I had my VAGCOM working correctly yesterday so I could have pulled the codes myself, but alas, I think I got it working this afternoon on my new laptop (stupid Windwos 7!. Hopefully codes have been written again for me to see.

There is what looks like a temp sensor mounted on the large coolant pipe running the width of the engine at the front. Is this the one I should be looking at, or is there a block mounted sensor elsewhere?

Thanks again.

[Proph3t]

So Thursday morning update

With a change to VCDS-lite from VAGCOM I was able to pull a single fault from the freshing cleared ECU after a few short starting attempts. Didnt turn the first time, but did all the others, sounds like when you have a flat battery. *Click*


VCDS-Lite Version: Release 1.1
Thursday, 29 March 2012, 07:56:45.
Control Module Part Number: 4D0 927 156 E
Component and/or Version: AG4 GETRIEBE 018 D24
Software Coding: 00016
Work Shop Code: WSC 34978
VCID: 2B2984AFCA0B
2 Faults Found:
00529 - Engine Speed Signal Missing
31-10 - Open or Short to Ground - Intermittent
00526 - Shareware Version. To Decode all DTCs
03-00 - Please Register/Activate


So as you said SilverD2, it might be that sensor on the bell housing. Lets hope its easy to get to and is the sensor itself and not some convoluted part of the loom under the dash

Then again I've chased errors like this on other vehicles only to find a sting of sensors masking each other in diag, only showing as faulty when another is replaced...ended up being the entire ECU in my Lexus SC300


EDIT: As listed on the Ross Tech wiki

00529 - Engine Speed Signal Missing

Possible Causes
-Wiring/Connectors from/to Engine Control Module faulty
Possible Solutions
-Check Wiring/Connectors from/to Engine Control Module
-Check Measuring Value Blocks (MVB)
Special Notes
-If stored in combination with 01312/01314, these must be rectified first.

[silverd2]

During cranking, if the engine speed sensor doesn't send a correct signal to the ECM, the fuel pump relay won't even be activated...can't start.

I'd check wiring from the sensor all the way to the ECM. Also I'd check the electrical connections in the E box for corrosion or any sign of water intrusion. If all looks good with connections and ECM, it could be a bad engine speed sensor.

The other code (00526) is with the brake light switch...bad switch, ABS problem, electrical connection, etc...nothing to do with starting problem though.