'01 s4 fuse 34, a ton of short to ground codes puzzle

[fuc.k_it_cut_it]

For all who like puzzles, 01 s4 approximately 110k with 16 codes (mainly short to grounds); abs light, traction control light, air bag light and oil temp sensor indicator on. Fuse 34 blows on key ignition and it's obviously in limp mode and runs 'well' (5lbs boost). So many 15amp fuses blown and countless hours of frustration.... Please help.

VAG:

VCDS Version: Release 15.7.4 Running on Windows 10 x64
Data version: 20160216
www.Ross-Tech.com

Monday,16,May,2016,09:27:12:17688

Chassis Type: 8D - Audi A4/S4/RS4 B5 (1995 > 2001)
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 06435
VCID: 34691398047E779EAA-515A

16 Faults Found:
16501 - Engine Coolant Temp. Sensor (G62)
P0117 - 35-10 - Signal too Low - Intermittent
17833 - EVAP Purge Valve (N80)
P1425 - 35-00 - Short to Ground
17938 - Camshaft Timing Adjustment
P1530 - 35-00 - Short to Ground
17955 - Boost Pressure Regulation Valve (N75)
P1547 - 35-00 - Short to Ground
17697 - Boost Pressure Control Valve (N249)
P1289 - 35-00 - Short to Ground
17529 - Oxygen (Lambda) Sensor Heating Circuit: B2 S2
P1121 - 35-00 - Short to Ground
17525 - Oxygen (Lambda) Sensor Heating Circuit: B1 S2
P1117 - 35-00 - Short to Ground
17861 - Exhaust Gas Temp Sensor 1 (G235)
P1453 - 35-00 - Open or Short to Plus
17865 - Exhaust Gas Temp Sensor 2 (G236)
P1457 - 35-00 - Open or Short to Plus
16486 - Mass Air Flow Sensor (G70)
P0102 - 35-00 - Signal too Low
17523 - Oxygen (Lambda) Sensor Heating: B1 S1
P1115 - 35-00 - Short to Ground
17527 - Oxygen (Lambda) Sensor Heating Circuit: B2 S1
P1119 - 35-00 - Short to Ground
16518 - Oxygen (Lambda) Sensor B1 S1
P0134 - 35-00 - No Activity
16538 - Oxygen (Lambda) Sensor B2 S1
P0154 - 35-00 - No Activity
17522 - Oxygen (Lambda) Sensor; B1 S2
P1114 - 35-00 - Internal Resistance too High
17548 - Oxygen (Lambda) Sensor; B2 S2
P1140 - 35-00 - Internal Resistance too High
Readiness: 0010 0101

-------------------------------------------------------------------------------
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 06435
VCID: 40814F4840C6DB3E3E-4F1E

7 Faults Found:
01367 - Central Locking Pump Run Time Exceeded (Likely Leak)
35-00 - -
01374 - Alarm triggered by Terminal 15
35-00 - -
01370 - Alarm triggered by Interior Monitoring
35-00 - -
01369 - Alarm triggered by Hood Switch
35-00 - -
01368 - Alarm triggered by Luggage Compartment Switch
35-00 - -
00991 - Interior Lights
28-00 - Short to Plus
00955 - Key 1
09-00 - Adaptation Limit Surpassed

-------------------------------------------------------------------------------
Address 45: Inter. Monitor Labels: 4B0-951-173.lbl
Part No: 4B0 951 173
Component: Innenraumueberw. D03
Coding: 00101
Shop #: WSC 06435
VCID: 60C1AFC8E006BB3E1E-4B96

No fault code found.

End-------------------------(Elapsed Time: 04:02)--------------------------


Things replaced:

fuel filter
fuel pump relay
N75
One egt
all 4 o2's
drivers side cam position sensor
timing belt and all the stuff from the kit
coolant temp sensor *(cleared code p0117)
spark plugs
new battery

fuse 34 still blows and still is in limp mode; and both still after:

Boost leak checked and held 10lbs
disconnected boost gauge for possible short
visual check of easily accessible wiring
visual check for loose solder or burn marks on ecu circuit board
disconnected: all o2's, both cam position sensors, both cam chain tensioner solenoids, oil temp sensor, coolant temp sensor, both egt's, n75, n249, fuel pump and maf/all the sensors on the airbox


Fuse 34 does not blow when the fuel pump relay is out, but blows when 'started' (fuel still in lines) I understand that the fuel pump relay powers one of the three + to the ecu. all visible engine grounds and fuse block grounds are good.

I'm thinking possible bad ecu... two test I know of:

1.) Try a loner ecu and possibly fry it
2.) Put my ecu in another s4 and have it possibly muck up some sensors or something...
3.) any other ecu test???

Any ideas? Been in limp for years and cannot figure it out, i'd rather not unwrap and check all the wiring for the circuits related to fuse 34 but seems like I might have to if it's not the ecu... Thank you all

[vavJETTAw36]

Check your grounds for that circuit. A bad ground could affect all of those on the same circuit.


Sent from my iPhone using Tapatalk

[fuc.k_it_cut_it]

vavJETTAe36,
haven't checked the exact grounds for fuse 34 (no access to diagrams) and the corresponding circuits; checked ground to plus fault on ecu grounds and all checked out fine, circuit diagrams to come... bentley is in the mail. thanks!

[vavJETTAw36]

A lot of those codes can be set by the popping of the fuse. Hard to tell which one is which


Sent from my iPhone using Tapatalk

[fuc.k_it_cut_it]

So I think I figured it out... I checked continuity from the rear pin of fuse 34 to ground, then unplugged the ecu and it was still shorted, then I started by individually unplugging the connectors behind the ecu. When I unplugged the orange connector, the short disappeared. Found online that the green with yellow stripe wire is a common power to a bunch of sensors coming from fuse 34. I unwrapped the harness following the green/yellow wire towards the engine bay and found a junction connecting that wire to 12 smaller green/yellow wires. I disconnected all of them and individually check ground continuity to all of them and found one short. I hooked up all of them except for the shorted one. Cleared codes and started it up, no epc or abs light and obviously no cel. Let it idle for 15 min, drove about 20 miles hammered on it a couple of times. Still only 5lbs of boost. Turned it off, started it back up and let it idle for a few minuets, turned it off and got no codes... I'm confused why I didn't get at least one code for the wire I disconnected... Possibly didn't drive it long enough to trigger any, but will tomorrow and post up what I find out.
Hope this helps anyone with a fuse 34 issue and finding the short.

[Papa_Dios]

So I think I figured it out... I checked continuity from the rear pin of fuse 34 to ground, then unplugged the ecu and it was still shorted, then I started by individually unplugging the connectors behind the ecu. When I unplugged the orange connector, the short disappeared. Found online that the green with yellow stripe wire is a common power to a bunch of sensors coming from fuse 34. I unwrapped the harness following the green/yellow wire towards the engine bay and found a junction connecting that wire to 12 smaller green/yellow wires. I disconnected all of them and individually check ground continuity to all of them and found one short. I hooked up all of them except for the shorted one. Cleared codes and started it up, no epc or abs light and obviously no cel. Let it idle for 15 min, drove about 20 miles hammered on it a couple of times. Still only 5lbs of boost. Turned it off, started it back up and let it idle for a few minuets, turned it off and got no codes... I'm confused why I didn't get at least one code for the wire I disconnected... Possibly didn't drive it long enough to trigger any, but will tomorrow and post up what I find out.
Hope this helps anyone with a fuse 34 issue and finding the short.

What was the resolution?

[Spur]

Were you able to trace that short? What was it? What sensors and/or relays are on that line(fuse 34)? Can we disconnect them all, clear the codes, replace the fuse, start the car and reconnect them one by one til the fuse blows...? Or some other logical efficient trail and error?

So I think I figured it out... I checked continuity from the rear pin of fuse 34 to ground, then unplugged the ecu and it was still shorted, then I started by individually unplugging the connectors behind the ecu. When I unplugged the orange connector, the short disappeared. Found online that the green with yellow stripe wire is a common power to a bunch of sensors coming from fuse 34. I unwrapped the harness following the green/yellow wire towards the engine bay and found a junction connecting that wire to 12 smaller green/yellow wires. I disconnected all of them and individually check ground continuity to all of them and found one short. I hooked up all of them except for the shorted one. Cleared codes and started it up, no epc or abs light and obviously no cel. Let it idle for 15 min, drove about 20 miles hammered on it a couple of times. Still only 5lbs of boost. Turned it off, started it back up and let it idle for a few minuets, turned it off and got no codes... I'm confused why I didn't get at least one code for the wire I disconnected... Possibly didn't drive it long enough to trigger any, but will tomorrow and post up what I find out.
Hope this helps anyone with a fuse 34 issue and finding the short.

[Nollywood]

Check your o2 sensors, especially the post-CAT ones.

They are in an area of high temperature. With the longer cables, they have been known to melt through the insulation, then the heater 12V+ comes into contact with the exhaust, or heat shield. This will pop fuse #34. In extreme cases (where the owners have fitted a higher amperage fuse) it can fry the ECU.

I would disconnect each post-CAT oxygen sensor with a good fuse in place, and see if it remains good. Just a way of isolating the problem.

[Spur]

Thanks man! I took a look at all of the wiring and connectors on my O2s sensors and sure enough, 2 were slightly roasted. At least one is still good and I can move on with my life thanks to you!!!!

[Spur]

I did the test you recommended and the first one blew the fuse. Quick and fairly painless. They were both post cat(if I didn't have cats could I tell you? Asking for a friend.) Grabbing a new O2 sensor tomorrow. Gotta find a way to alleviate the risk of this happening again. Suggestions?

[Nollywood]

Glad you managed to isolate the problem.

When you replace the sensors, make sure they are clipped securely to the underbody, out of reach of the downpipes. Especially where it snakes up the transmission tunnel to the firewall.

You can get heat-resistant wrap around areas close to any heat source. I believe Audi do these as sleeves with snap buttons.

[Spur]

I only replaced the one that was bad. I wrapped it in heat insulated tape and carefully snaked it as far up and out of the way as possible using a coat hanger(should have filmed or took some pics, I had momentum so I didn't stop too lol). Zip tied everything I could see that was threatened by the exhaust in safer spots... No codes or blown fuses. Car runs like a dream, thanks again!!!

[Nollywood]

Glad I could be of help.

[christianb5s4]

You can use zip ties to keep the wires away from heat sources like the exhaust. Also, I use this type of product on my ECS R8 coilpack harnesses to shield it from the exhaust manifolds. It's been on there a year directly above the exhaust manifolds and has done a phenomenal job and still looks brand new.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1