Stalling, relay/throttle body clicking...just like the others, only different!

[mhkung]

UPDATED 8/18/2017 with VCDS scan!

Ok folks, I think I've exhausted the search function on this one...Hoping some of the heavy hitters here have some thoughts or insights.

S4 avant 6 speed. 140k on the clock. Bone stock, no aftermarket electronics.

First, an obligatory VCDS scan.

Saturday,24,June,2017,22:15:55:49885
VCDS -- Windows Based VAG/VAS Emulator Running on Windows XP x86
VCDS Version: 17.1.3.0
Data version: 20170220 DS267.3
www.Ross-Tech.com


Chassis Type: 8D - Audi A4/S4/RS4 B5 (1995 > 2002)
Scan: 01 02 03 08 15 16 17 25 35 37 45 55 56 57 67 75 76 77

-------------------------------------------------------------------------------
Address 01: Engine Labels: 078-907-551-AZA.lbl
Part No: 8D0 907 551 M
Component: 2.7l V6/5VT G 0001
Coding: 06711
Shop #: WSC 87119
VCID: 34669B4004F9B2E13D-5140

4 Faults Found:
18010 - Power Supply Terminal 30
P1602 - 35-10 - Voltage too Low - Intermittent
17539 - Oxygen (Lambda) Sensor; B2 S1
P1131 - 35-10 - Internal Resistance too High - Intermittent
17965 - Charge Pressure Control
P1557 - 35-10 - Positive Deviation - Intermittent
18011 - Internal Control Module
P1603 - 35-10 - Failed Self-Test - Intermittent
Readiness: 0000 0000

-------------------------------------------------------------------------------
Address 03: ABS Brakes Labels: 8D0-907-389.lbl
Part No: 8D0 907 389 E
Component: ABS/ESP allrad D56
Coding: 04395
Shop #: WSC 06435
VCID: 3560A6440F83ABE90A-5140

2 Faults Found:
18034 - Powertrain Data Bus
P1626 - 35-00 - Missing Message from TCU
18258 - Powertrain Data Bus
P1850 - 35-00 - Missing Message from ECU

-------------------------------------------------------------------------------
Address 08: Auto HVAC Labels: 8D0-820-043-1D.lbl
Part No: 8D0 820 043 P
Component: A4 KLIMAAUTOMAT D58
Coding: 00160
Shop #: WSC 63351
VCID: 2D508E24E7D3E32972-2592

No fault code found.

-------------------------------------------------------------------------------
Address 15: Airbags Labels: 8D0-959-655-AI8.lbl
Part No: 8D0 959 655 G
Component: Airbag Front+Kopf 2002
Coding: 00306
Shop #: WSC 00254
VCID: 3A7AB578269D4491E7-519A

No fault code found.

-------------------------------------------------------------------------------
Address 17: Instruments Labels: 8D0-920-xxx-17.lbl
Part No: 8D0 920 981 B
Component: B5-KOMBIINSTR. VDO D12
Coding: 02264
Shop #: WSC 08701
VCID: 2B54803CD9C7ED196C-5140

1 Fault Found:
01314 - Engine Control Module
49-10 - No Communications - Intermittent

-------------------------------------------------------------------------------
Address 35: Centr. Locks Labels: 8D0-862-257.lbl
Part No: 8L0 862 257 N
Component: CV-Pump, Alarm, RC D16
Coding: 16140
Shop #: WSC 63351
VCID: 408EC79040411E41A9-4EB2

2 Faults Found:
01367 - Central Locking Pump Run Time Exceeded (Likely Leak)
35-00 - -
00991 - Interior Lights
28-00 - Short to Plus

-------------------------------------------------------------------------------
Address 45: Inter. Monitor Labels: 4B0-951-173.lbl
Part No: 4B0 951 173
Component: Innenraumueberw. D03
Coding: 00102
Shop #: WSC 63351
VCID: 60CE2710E0817E4189-4B66

No fault code found.

-------------------------------------------------------------------------------
Address 55: Headlight Range Labels: 4B0-907-357-AUT.lbl
Part No: 4B0 907 357
Component: LEUCHTWEITEREGLER D004
Coding: 00012
Shop #: WSC 63351
VCID: 65C03604FFA31B697A-517C

No fault code found.

-------------------------------------------------------------------------------
Address 56: Radio Labels: 8D0-035-1xx-56.lbl
Part No: 8D0 035 195 A
Component: Radio D00
Coding: 00110
Shop #: WSC 63351
VCID: 24466B00B4192261AD-4B00

No fault code found.

End-------------------------(Elapsed Time: 04:25)--------------------------

Recent work--this problem predates all of these repairs
- New timing belt, water pump
- New Ignition switch
- New fuel pump
- New spark plugs
- New crank position sensor
- New battery
- Not new, but I do have a spare M box ECU that I've been using (more to follow on this)

The issue:
While driving, at random times, my car stalls. Sometimes it bucks right back, but most of the time not. I can go weeks without a peep, or it can happen multiple times in a matter of minutes. When it stalls, I get a beeping sound from the instrument cluster, and then I get a telltale clicking noise from the throttle body, fuel pump relay, possibly other parts. The clicking keeps going as long as the key is turned on. If the clicking is there, the car will not start back up (engine cranks, but no start). My VCDS cannot 'see' the ECU as long as there is clicking.

If the fuel pump relay is unplugged, the clicking ceases. Also, once the relay is removed, the VCDS can scan the ECU.

I can override the fuel pump relay, either by jumping the leads, or manually, and the fuel pump does prime even with the clicking. BUT, the car still doesn't start even when forcing the relay 'on'. This tells me there's gas, but no spark. I have not yet confirmed this--because 'unfortunately', the car is working fine right now. (is the a VCDS code for faulty ignition switch or spark plugs?)

My issue is JUST like this


And this:


Both videos ended up diagnosing the problem as a loose grounding bolt behind the coolant reservoir

And as described in the following threads
#1--unresolved thread
#2--loose grounding bolt behind coolant reservoir
There's more, but you get the point. All signs from the above point to a bad sensor ground, possibly caused by a bad physical ground.

I've inspected and my physical grounds all seem to be completely fine. Have not checked continuity on all ground wires just yet--but the problem is intermittent. If I pull, tug and jostle the ground wires, nothing happens. Additionally, I cannot reproduce the issue if I manually disconnect the ground while the engine is running (yes, the engine shuts off, and yes, there is clicking for a time, but then it goes away--it does not click continuously like it does when its acting up on me). Also, I've pulled on the wires in the ECU wiring harness to no effect.

Possible Clues:
- The car can stay like this for weeks at a time, then randomly be fine one day (it can also drive fine for weeks at a time as well)
- The ECU gets very hot very quickly when this issue is occurring (bad ground?)
- This is not universally true, but it seems to get worse when its raining out. I got caught out twice in the crazy downpours we had in Houston last spring.
- If I swap the ECU, the car starts right back up every. single. time. Now, it might only last me 5 minutes (or 5 days)...it's a mystery. I once stalled out 3 times on the way home from work, one time literally on a railroad crossing (also in the midst of a flash flood). Thankfully, I got it started immediately!
- Sometimes, when the clicking is occurring, the fuel pump will not run. Even if I jump the relay, it will not run. But others, the fuel pump will run, but still, the engine will not ignite
- Under normal circumstances, the fuel pump seems only to prime randomly (see related thread I started)
- When the clicking is occurring, VCDS cannot communicate with the ECU. However, if I unplug the fuel pump relay, it can. The above scan was done with the FPR unplugged.
- There was a critter living on my old fuel pump for some time. This led to replacement of the fuel pump, which ran fine, but had corroded connections that my mechanic suspected caused shorts (possibly damaging other wires/parts in the process). He had to run some new wires to power the fuel pump.
- One time, when going to swap my ECU, when taking the ECU box cover off, it got caught on the ECU wiring, and when I pulled on the cover/wiring, that made the click go away. I cannot reproduce the issue, even if I pull like mad at the ECU
- I have not yet checked to see if I'm getting spark

Really appreciate you reading this far and hope you can shed some light!

[mhkung]

bump with new VCDS scan

[MacDaddy]

Maybe you could run a new ground for the affected circuit (fuel pump?) i also have a suspicion its a bad ignition switch, but the swapping ecu fixing it doesnt make much sense, what about unplugging and plugging in the same ecu instead of a swap?

[mhkung]

Maybe you could run a new ground for the affected circuit (fuel pump?) i also have a suspicion its a bad ignition switch, but the swapping ecu fixing it doesnt make much sense, what about unplugging and plugging in the same ecu instead of a swap?

Good idea with running the new physical ground. Will do that.

The unplugging and re-plugging the same ECU works sometimes, but def not 100%. I think it might depend on how long it's unplugged.

[Mille Bornes]

I wish I could offer some help but I'm just here to say I appreciate how you formatted your OP. Much easier to read than the standard wall of text lol

[AudiTechS4]

Ok so I was having the same issue your having and messaged you about it. Throttle body clicking , no start while clicking and no fuel while clicking. Well mine was an easy fix and might be your issue as well. I spent all morning going over my harness and like an idiot I never connected the main engine harness ground and it's was barely making contact with the body. I would suggest overlaying that ground. I'll look on Monday for the ecu pin out of it to verify it's not spliced

[mhkung]

I never connected the main engine harness ground and it's was barely making contact with the body. I would suggest overlaying that ground. I'll look on Monday for the ecu pin out of it to verify it's not spliced

You mean the really thick 'main' ground? I checked that and all's good. I do think I'm going to run new grounds from the engine and the ECU (pins 1,2).

[AudiTechS4]

no the one that grounds under the coolant res off of the engine harness

[mhkung]

For anyone who runs into this -- I ran a new ground to pin 1 of the ECU and the issue is gone. I never pulled the old ground wire out, but assume that there was a crack in the wire, or a burn through the housing or something.

So, it turns out my issue wasn't all that different after all.