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-   -   V70: Gearbox Tg-81sc no comms - 2015 v70 (https://www.volvoforums.org.uk/showthread.php?t=292841)

ymc30 Mar 14th, 2019 19:01

Tg-81sc no comms - 2015 v70
 
1 Attachment(s)
Hi guys I desperately need your help as I am running out of ideas :(

Foreplay:
I've bought a 65 plate V70 D4 with a failed engine (D4204T5) which is an 8 speed auto (TG-81SC). I also happened to have a working engine-gearbox from an accident damaged V70 - same engine/gearbox combo.

Last week I dropped the failed engine with the gearbox and put the working one in. I did NOT touch any modules I even failed to change over the TCM from the non working engine/gearbox unit (where the gearbox is supposedly was working)

The car started first time and was running OK although next day I had "reduced transmission performance" but after I cleared the DTCs it went away and the gearbox was working fine but I still had some TCM related faults but hey, who cares?!?


The fun bit:
Today I took the TCM from the failed engine/gearbox combo (which TCM belongs to the car originally) to get rid of the DTCs.

Disconnected the battery, changed the TCM, reconnected everything - since then the car could not see the gear position (Shift gear to P) and refuse to start.

No connection with TCM and strangely no comms with power steering. Also no gear selection symbol on the RH side of the speedo.
Please see DTCs attached.

Any help would be appreciated :)

KBB Mar 15th, 2019 05:42

If scan tool is showing no comm with sub modules the I would be checking powers and grounds to those modules.

If you have been removing and replacing engine and transmission then there may be a missing ground.

ymc30 Mar 15th, 2019 09:26

1 Attachment(s)
Quote:

Originally Posted by KBB (Post 2504370)
If scan tool is showing no comm with sub modules the I would be checking powers and grounds to those modules.

If you have been removing and replacing engine and transmission then there may be a missing ground.

Thanks for the reply.

I swapped everything by lowering the subframe and followed it up in Vida.
Car was running after the swap OK although with fault codes (supposedly because the TCM was from the other car) So everything was connected properly.

This problem occurred after the swap of the TCM which seemed to be an easy process. Battery disconnected, a few bolts taken out, swapped the module (made sure it is properly seated), job done. NOT :(

Since then I checked the fusees for the TCM (all good), swapped back the other module, no joy.

I am thinking more along the lines not waiting long enough before taking the TCM out after the battery disconnected so something burnt out?!

Symptoms are:
- no connection to TCM
- strangely no connection to PSM (maybe a telltale for someone)
- Park position is not recognised - not shown on the right side of the speedometer (probably due to no comms with TCM)

ymc30 Mar 21st, 2019 09:56

Solved
 
Just a quick follow up for anybody interested...

After having half of the car taken apart I gave up. Next day put the whole thing together and the problem was gone.

The Start-stop system has some fuses in the "engine compartment cold zone" which is really - I mean really - hard to reach hence the reason the car was in pieces. This meant that the supply battery was also disconnected overnight alongside with the main one. I don't know whether this done the trick?!?

Also first I connected everything up except the TCM which wasn't even plugged in to the gearbox. Obviously engine did not start.
Next up I connected the TCM to the wiring loom but not to the gearbox. This resulted a bunch of DTCs related to gearbox pressure sensors, etc. Engine refused to start obviously.
Finally everything properly connected - engine started first time. Still has some TCM related DTCs but I'll figure them out later.


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