D2 gearbox scare (A8L 2000)

[johnny_quattro]

Here are the results from the Lithuanian jury (as per Eurovision parlance):

OBDeleven data log
Date: 2016-05-08 09:53
VIN: WAUZZZ4DZYN011439
Car: Audi A8
Year: 2000
Engine: AQF
Mileage: 14930 KM
---------------------------------------------------------------
01 Engine Control Module 1
System description: 4.2L V8/5V G 0001
Software number: 4D0907560AK
Coding: 05753
Trouble codes:
No trouble codes found
---------------------------------------------------------------
02 Transmission Control Module
System description: AG5 01L 4.2l5V RdW 1313
Software number: 4D0927156CT
Coding: 00001
Trouble codes:
P0605 - Internal Contr.Module ROM Test Error
Intermittent
---------------------------------------------------------------
03 Brakes 1
System description: ABS/ESP allrad D26
Software number: 4D0907389E
Coding: 08397
Trouble codes:
No trouble codes found
---------------------------------------------------------------
08 Air Conditioning
System description: A8-Klimavollautomat D12
Software number: 4D0820043Q
Coding: 00081
Trouble codes:
00713 - Left air flap motor for center vents locked or has no voltage supply
Intermittent
00715 - Rear footwell vent pos. motor locked or has no voltage supply
Intermittent
01274 - Air Flow Flap Motor locked or has no voltage supply
Intermittent
00727 - Potentiometer in positioning motor for defrost flap Open circuit/short circuit to B+
static
00730 - Potentiometer in positioning motor for center vent Open circuit/short circuit to B+
static
00731 - Potentiometer in positioning motor for left footwell flap Open circuit/short circuit to B+
static
00733 - Potentiometer in positioning motor for rear footwell vent Open circuit/short circuit to B+
static
01592 - Air quality sensor Electrical malfunction in circuit
Intermittent
01273 - Fresh air blower Control difference
Intermittent
---------------------------------------------------------------
11 Engine Control Module 2
---------------------------------------------------------------
15 Airbag
System description: Airbag Front+Kopf 1000
Software number: 4D0959655P
Coding: 01427
Trouble codes:
01578 - Airbag -off- indicator lamp, frt.pass. side Open circuit/short circuit to ground
Intermittent
---------------------------------------------------------------
16 Steering Column Electronics
System description: 907 487 A Lenkradelektronik D 11
Software number: 4B0
Coding: 00100
Trouble codes:
No trouble codes found
---------------------------------------------------------------
17 Dash Board
---------------------------------------------------------------
18 Auxiliary Parking Heater
---------------------------------------------------------------
25 Immobilizer
---------------------------------------------------------------
35 Central Locking Control Module
System description: CV-Pump, Alarm, RC D13
Software number: 8L0862257P
Coding: 13130
Trouble codes:
01367 - Pump cut-out for central locking
static
01366 - Opened due to crash signal
static
01365 - Lock/unlock switch/interior locking switch Short circuit to ground
static
00991 - Interior lighting Short circuit to B+
static
00956 - Key 2 Value above upper adaptation limit
static
01134 - Alarm horn Terminal 30 missing
Intermittent
01134 - Alarm horn internal voltage supply
Intermittent
01134 - Alarm horn No communication
static
---------------------------------------------------------------
37 Navigation
---------------------------------------------------------------
45 Interior Monitoring
System description: Innenraumueberw. D05
Software number: 4D0951177B
Coding: 00001
Trouble codes:
No trouble codes found
---------------------------------------------------------------
55 Headlight Regulation
System description: dynamische LWR D02
Software number: 4B0907357C
Coding: 00001
Trouble codes:
00774 - Left rear level control system sensor Short circuit to B+
Intermittent
---------------------------------------------------------------
56 Radio
---------------------------------------------------------------
57 TV Tuner
---------------------------------------------------------------
65 Tire Pressure Monitoring 1
---------------------------------------------------------------
67 Voice Control
---------------------------------------------------------------
75 Telematics Communication Unit
---------------------------------------------------------------
76 Parking Assistance
System description: Parkingsystem A8 RDW D06
Software number: 4D0919283
Coding: 01108
Trouble codes:
No trouble codes found
---------------------------------------------------------------
77 Telephone



The key error here is for the transmission, as originally reported:

P0605 - Internal Contr.Module ROM Test Error
Intermittent

Like I said though, I've had no further occurrences so I'm tempted to leave it as it is, unless someone has any advice to offer?

[johnny_quattro]

I've had further multiple occurrences since my last post way back in the mists of time so here's an update on the situation.

Gearbox started going in to limp-home mode on a fairly regular basis. I called the gearbox people who highly doubted that there was a physical fault with the newly-repaired gearbox overhaul that they did and they offered to scan the car for free. They also told me not to cane the engine revs when trying to move off from a start or I'd fry the ATF. I'm not the sort of person to do drag strip starts at the traffic lights but it made me start to drive the car very gingerly. I contacted the forum sponsors as my gearbox TCU was throwing up intermittent fault codes and ROM errors but my particular variant (CT) wasn't in stock. After a good few months of embarrassing events at traffic lights where the box had gone (into limp mode) and me trying to pull away at anything approaching walking speed resulted in lots of revs from the engine and not something I wanted to continue doing. After months of searching, an exact match was found. Apparently, the CT version was only doing the rounds for 4 months, hence the rarity - see attached photo.

Ordered, package turned up the next day and to fit it was simply 'plug and play'. Removed the old unit which looked immaculate and replaced it. A8Parts said it was unusual for the unit to fail but mine was certainly a duff unit. Replacement TCU working like a champ, and my faith in humanity and German engineering has now been restored.

Gear changes are now smooth, pick-up is instantaneous and it doesn't seem to hunt stupidly for gears. Plus my instrument display is now clean and free of red PRND432!

[David's8]

Good to hear a result (eventually!) Would it have mattered if another variant of the TCU was used on the AQF engine? Was there any indication of cause of failure?

[Ameiseuk]

I have OBDEleven and have just upgraded to pro - lots of info on there and a very good app.

[johnny_quattro]

The failing/failed TCU was in immaculate condition when I had a look under the bonnet. Spotless and with no sign of water ingress at all, which was my initial concern. It was flagged up on OBDeleven as an intermittent ROM failure, and the situation only deteriorated over time. The car would go into limp-home mode even when sitting on the drive with the keys in the ignition, and the engine wasn't running. That cemented it in my mind that it must be the TCU for the gearbox, as the gearbox was only repaired at great cost in April 2014.

After I'd fitted the replacement, the car was idling for 5 minutes whilst I double-checked for any faults with the OBDeleven device. Went for a quick spin to see how it was performing and it had transformed the way the car behaved. Gearbox creep was reduced somewhat too, although that might be just me as I was feeling elated at having fixed it myself lol

With regard to the CT variant of the TCU and matching it to the AQF engine, I'm not sure if it would have made a difference or become a show-stopper if I'd changed it to another non-matching TCU. From my computing brain perspective, I wanted to replace like-for-like without introducing any other issues. Perhaps you can do that but I didn't want to risk it.