Trouble code p0863 TCM

concord7 · Post by **concord7** » 15 May 2016, 02:19

Hi, just joined this forum because I just purchased a 2004 XC70. I owned a volvo years ago that over 250k on it if I remember correctly. I really liked that car. This XC70 has 196k on it and just threw code p0863 the TCM. The car seems to be slow going into first and the gauges on the dash come on at start then quickly go down and and don't work. Car seems to run fine and once moving shift ok.

I am going to pull the ECM and TCM and clean the contacts hopefully this clears up the problem.

If anyone has had this problem or has any thoughts I would appreciate it. Will post again when I find a solution.

Thanks concord7

Post by **packetfire** » 15 May 2016, 07:41

The p0863 code is a communications issue between the TCM and the ECM, the TCM and the CEM, or maybe the BCM stomping on the bus, and fouling things up for the other modules. (See communications network diagram for a 2004 v70 below)

But it would be strange to ONLY have a p0863, and also have the gauges thrashing or going dead.

Random thrashing of the gauges on dash (DIM) would not be affected by an issue on the TCM/ECM side of the CEM, as there is a separate connection to the DIM from the CEM. The CEMs themselves have been problematic for many pre-2005 v70s and xc70s, as they lacked the heat sinks on the chips in the metal-shielded enclosure on the DIM circuit board.

But gauges going catatonic without throwing an error code of their own would be unusual - does the whole instrument cluster go dead, or just the gauges, with the message display and the idiot lights still working?

concord7 · Post by **concord7** » 15 May 2016, 10:02

Thanks like I said new to this car. Yes you are correct there are 4 codes in total p0863, u0073, p0504, p0571. the gauges the needle swing up on start then go right back as for the lights the check engine stays on and the srs light.

I am headed out now to tinker around with it. Thank you, I will try and be clearer on my end

concord7 · Post by **concord7** » 15 May 2016, 13:49

I unhooked the battery and pulled and cleaned the ecm and the tcm contacts and now everything seems to be working. I don't know if I cleared the codes for awhile or if I was having a contact problem. I will keep posting as I learn more. If anyone knows feel free to let me know.

Thanks

concord7 · Post by **concord7** » 24 May 2016, 00:14

I got my check engine light back. Going to get the codes tomorrow. Changed the crank case breather system out over the weekend hope I didn't mess anything up. thanks for the help. Rough at idle after check engine light came on. Will post any new information. Thanks

NewVolvoOwner-S60 · Post by **NewVolvoOwner-S60** » 16 Jul 2017, 10:44

I have a 2004 S60 2.5T AWD and was trying to open the trunk using the remote while siting in the car pressing the unlock button and the trunk button, I think the car was running (can't remember). When I tried to drive away the car had very little power and I noticed that the display on the dashboard was still showing that is was in park and the check engine light came on. I turned the car on and off seeing that would fix it but it didn't work. I got out and put the key in the driver side door and did the lock/unlock 3 times, got in and now the car was working but the check engine light would not go away. My Harbor Freight scanner showed me only one code, P0863. I erased the code to clear the check engine light. I hope it doesn't come back, the car is running fine right now. I'm wondering if messing with the remote while in the car had anything to do with this?

22volvo · Post by **22volvo** » 22 Jul 2018, 15:02

I'm picking up this year old thread in case the OP found his solution.

Similar issue for my 2004 V70 2.5T, 223K miles. Actually, the issue has occurred about 10 times in the 8 years I've had the car.
- Usually on HOT days.
- Dash gauges go to zero, driver's window and door lock controls don't work, turn signals don't work and the AC quits.

This time we felt transmission bumps, about 7 over 10 minutes. On the last bump the gauges and AC went out, etc.
Limped it home and hooked up the scanner w/o ever turning off the engine. Couldn't get to all the modules, only $11 whichever that is, and it had the code P0863.
After stopping and restarting the engine, everything was back to normal including comms to ABS, ECM, SRS and TCM. The BCM, ECM and SRS all latched some flavor of Comm Fault but not the TCM.

The last time I had the problem (bout 3 years ago) I re-seated the ECM and TCM w/ dielectric grease on the contacts and made sure their cooling flow was working.
This time I intend to pull the CEM and grease those contacts. Since it happens on hot days, I'll look at a way to cool it with forced air.

Post by **abscate** » 22 Jul 2018, 18:14

The 2004 CEM has a known heat sink issue so start there. Don’t touch the ECM/TCM until you work the CEM. We have one person who has bricked these messingwith them recently.

22volvo · Post by **22volvo** » 24 Jul 2018, 12:24

Agree w/ only affecting one component at a time. So my CEM got heat sinks and and a fan. Had to clear all the comm related codes from the other components. Wife is out testing it now.

Local Frys store had a "Rasberry Pi" heat sink kit - I bought 4.

: heatsinkAndFanUsed (Copy).jpg (19.21 KiB) Viewed 6353 times

I saw a fan that would work and show it in the picture below but I used one from my parts bin.
Parts bin fan used is a brush-less DC w/ .04 amp draw.

: gen-fan (Copy).jpg (25.48 KiB) Viewed 6353 times

The cover was easy to remove - just slip something into the corner.

: remove-cover (Copy).jpg (39.66 KiB) Viewed 6353 times

After using alcohol to clean the tops of the chips, 4 of the larger heat sinks fit the large chip while 3 of the smaller heat sinks fit the other. The coating on the board (and the chips) was not removed. The heat sinks had a peel and stick thermal layer so that is what I used.

: installingHeatsinks (Copy).jpg (46.99 KiB) Viewed 6353 times

For the airflow....

: makeAHole (Copy).jpg (39.51 KiB) Viewed 6353 times

The offset is intentional. If the fan were centerd over the target area it would create a high pressure area with less air flow because of the metal enclosure. Offsetting the fan allows the air to circulate. You'll also note that both the metal cover and the plastic cover of the removed module are not reinstalled.

: noteHoleOffset (Copy).jpg (40.51 KiB) Viewed 6353 times

Tie wraps.

: mountingFan (Copy).jpg (29.73 KiB) Viewed 6353 times

Mechanical completed.

: finished (Copy).jpg (34.3 KiB) Viewed 6353 times

The positive lead of the fan was tied to the switched output of relay CMI22 - the wire is Violet w/ a White stripe right behind that relay.
The ground lead ended up at the door post connection.

22volvo · Post by **22volvo** » 14 Aug 2018, 21:29

So at the end of the day, the Texas heat hitting over 100 degrees means it doesn't matter if heatsinks and fan are installed. The CEM is problematic on hot days.
Off to xemodex (in Canada) it went. Fast turnaround. 2000 miles on the replacement and no issues.