S4Per

(sent to andy already)


1. Transmission will go into limp mode, then come out of limp mode, and go back into limp mode, i.e. intermittent.
2. When in limp mode, there is no way I can get into the transmission module in Vag-com...it can't connect.
3. In the below auto scan you will find ECU, ABS, and Instruments reporting
a. 18034 - Powertrain Data Bus: Missing Message from TCU
P1626 - 35-00 - -
4. I disconnected then reconnected the TCU which kept it out of limp mode for 20 minutes or so.
5. The traction control and ABS light will be lit in the instrument cluster when the fault/limp mode occurs.

Any thoughts? The TCU costs about $1600 I think, so I'd like to try and eliminate all other possibilities prior to replacing it.

Thanks,
Per

Friday,05,October,2007,08:18:34:51234
VAG-COM Version: Release 704.1
Data version: 20070723
Chassis Type: 8D - Audi A4 B5
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 AA
Component: 2.7l V6/5VT G 0003
Coding: 06751
Shop #: WSC 63351

No fault code found.
Readiness: 0110 1101

-------------------------------------------------------------------------------
Address 03: ABS Brakes Labels: 8D0-907-389.LBL
Part No: 8D0 907 389 E
Component: ABS/ESP allrad D56
Coding: 04397
Shop #: WSC 06435

1 Fault Found:
18034 - Powertrain Data Bus: Missing Message from TCU
P1626 - 35-00 - -

-------------------------------------------------------------------------------
Address 08: Auto HVAC Labels: None
Part No: 8D0 820 043 Q
Component: A4 KLIMAAUTOMAT D58
Coding: 00160
Shop #: WSC 63351

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: 00304
Shop #: WSC 63351

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 42286

3 Faults Found:
01300 - Control Module for Navigation with CD-Rom (J401)
49-00 - No Communications
01315 - Transmission Control Module
49-00 - No Communications
01311 - Information Data Bus
37-10 - Faulty - Intermittent

-------------------------------------------------------------------------------
Address 35: Centr. Locks Labels: 8L0-862-257.LBL
Part No: 8L0 862 257 N
Component: CV-Pump, Alarm, RC D16
Coding: 15208
Shop #: WSC 63351

No fault code found.

-------------------------------------------------------------------------------
Address 45: Inter. Monitor Labels: 4B0-951-173.LBL
Part No: 4B0 951 173
Component: Innenraumueberw. D03
Coding: 00101
Shop #: WSC 63351

No fault code found.

-------------------------------------------------------------------------------
Address 55: Xenon Range Labels: 4B0-907-357-AUT.LBL
Part No: 4B0 907 357
Component: LEUCHTWEITEREGLER D004
Coding: 00012
Shop #: WSC 63351

No fault code found.

End

diagnosticator1

The cause of the problem is almost for sure, a bad connection for the CAN High or CAN Low buss wires, at or near the TCU. Examine the terminals in the harness connector to the TCU, make sure none of the wire terminals are damaged from test probes, etc, and not otherwise bent and unable to maintain contact with the mating pin terminal tightly. The symptom you described, is a classic case of a loose connection, where the symptom alternates with normal operation. Using a DVM, on continuity measurement setting, connected to the CAN High wire at the connection station under the left kick panel, and the same wire at the TCU harness connector, wiggle the harness along the run and see if the continuity "makes and breaks", at some point in the harness. Do the same test on the CAN Low buss wire. Check for shorts between the CAN buss wires and ground, and for any short circuit between the two CAN buss wires. If there are damaged terminals in the TCU harness connector, they must be replaced.

S4Per

I've spent more hours underneath that kick panel in the last 2 days than I'd like, but I can't clearly identify the 'connection station' - - can you help me locate? Any further description of its appearance?

TIA,
Per

diagnosticator1

The various harness connectors are mounted on a bracket. One or more of the harness connectors has the drive train can buss wires in it. Refer to the wiring diagrams for the Drive Train CAN buss for specific connector ID.

S4Per

EDIT: Thought it was a lose TCM cover, but that only exposed symptom. See post above, GIAC found bad solder joint; expecting this to be root cause.

Thanks for all the pointers! Still amazed that this was it.<ul><li><a href="https://forums.audiworld.com/s4/msgs/2716793.phtml">Can't believe it was that.</a></li></ul>

Andy@Ross-Tech

For future reference, it would have helped greatly if you mentioned your TCU was modded.

S4Per

Sorry, my fault. In most other conversations I think I mentioned it.

S4Per

I should have it back next week and expect(fingers crossed, knocking on wood) that this was root cause.

diagnosticator1

I wish I could get a Tip Chip for my B6 A4! Thanks for the updates!

S4Per

they resoldered it, got the TCM back last night and everything is working as normal again.

Glad that's over :-)