BlackMammoth

Hi Guys,

I hope to get expert advise on how to fix my problem.

It s going into limp mode then you start with big kick. Cannot return to reverse lever, only if turn off engine.

I scanned it and got these codes one before last time:

P240C CAN Signal Selector Lever Position N15/5 Implausible
P1856 Fault in Selector Lever Test
P2000 Brake Pressure Implausible
P2001 CAN communication is faulty
P2314 CAN Communication N73 (Electronic Ignition System Module) Faulty
P2315 CAN Communication A1 (Instrument Cluster) Faulty
P2316 CAN Communication A1 (Instrument Cluster) Faulty
P2502 Gear Implausible or transmission slipping

Took it to garage to change oil, gasket, oil filter and plug. It was ok for short time. And got bad again.

Scanner guy said get rid of this car as trying to repair it will be nightmare. However advised it could the problem with TCU transmission control unit.

I also came across doing my research it could also be other faults like, oil leaking into cable or contacts, not quite sure exactly.

Please any advise is welcome.

tjts1

Yes, leaking ATF from the transmission can wick it's way the wiring harness into the TCU. It's a common problem on the 722.6. Find the TCU and check for oil on the wiring, in the plug and in the TCU itself. Clean it all with isopropyl alcohol, clear the codes and see if the problem goes away.

BlackMammoth

Here are some updates.

1.O ring on plug, has been changed by mechanic (i hope so, worth checking)
2. Opened passenger side UK foot place. Found lots of fluid on cables and some inside of tcu.
3. Opened unit and cleaned with brake cleaner all contacts and cables
4. Put it all together
5. Took it for drive test. Still in limb mode
6. Called our scanner guy. Couldnt communicate to tcu
7. Opened again tcu. Cannot see any visual fault
8. Checked fuses 58 and 61 were missing. Put new fuses in
9. Tried to find if any valtage coming into unit. No luck

SO now i have a few questions
1.Please any ideas what cable i need to be checking for power and earth?
2.And also how to check if unit in working condition?
3. If i get replacement unit of ebay only £20 do i need to code it?

tjts1

Reflow the large solder joints where the pins from the plug go into the PCB. Those tend to develop micro cracks and when ATF gets into the cracks they get insulated.

If you replace the TCU you will need to have it coded to your VIN #.

You can buy an icarsoft i980 scanner to read and clear TCU and all other computer modules in the car. It's $120 in the US. Probably cheaper than having a guy come out.

BlackMammoth

Thanks for advise. I will resolder that.

Does anyone know how to check if power coming into unit. What is that supposed to be?

BlackMammoth

I just checked all cables on two plugs. None of them got power of 12v.

i checked fuses box, as i mentioned 58 and 61 had no fuses at all. I did put fuses in yesterday.

today i am checking for power on 58 and 61 and 58 has no power.

there is also relay. Not sure how to check it with mulitmeter.

any electricians here it please?

romeovictrbravo

I have been going through the gearbox in my ML which had two TCM failures. In my case the 12volt to the trans (activates the solenoids) was not working .There is a power supply on the TCM's board and in my case both failed .I am now fighting with a new 2nd hand one which will sometimes communicate with the isoft scanner ,sometimes not. I only get code P2502 though which the scanner cannot get rid of. I will try resoldering the board tomorrow .I have replaced the contact plate and pilot bush using genuine Merc parts as i had failures with elcheapos i bought on ebay. .I am sure one of these dodgy plates blew the two TCM's. On one plug into the TCM there three wires,the blue and red are 12volt and the brown is earth The other leads going to the trans activate the solenoids and recieve the signal from the speed sensor magnets . In case you were wondering why the trans fluid cuases so many problems, it's a special fluid which picks up the microscopic metal particles ,hence the magnet in the bottom pan. When the fluid gets into the plug and up the lead it buggers everything as the TCM gets all the wrong signals.

BlackMammoth

I had an electrician came few days back and he was checking everything. My TCM was blowing off fuses and funny thing I thought fuse for TCM located in the front under bonnet number 58 or something, but he found fuse 13 on the back boot blowing as soon as he plugs TCM. I got second hand of ebay today, plugged it to car and still limb mode. Paid 40 electrician and 16 for parts and still no results, I am giving up man.

Anyone know what else could it be

tjts1

The new tcm needs to be coded to your car's vin number. If the tcm vin doesn't match it work communicate with the rest of the car.

romeovictrbravo

You have a faulty contact plate in the trans itself. Your best bet would be to get an electrician who knows his stuff or get a trans shop to drop the pan on your trans and replace the contact plate, the socket and possibly the wiring loom for the trans. I had a similar thing happening to me but it was after two blown up TCM's that I found a new contact plate i had fitted was garbage made in China . You could also possibly have the same fault i started with, the trans has a catastrophic failure. A bearing let go in mine at 260,000 and spread bits of the bearing through the trans .I have had this going on for 18 months now with no real solution.

BlackMammoth

I fitted second hand tcm from ebay and at first car didnt even start, i mentioned it before. Old tcm was still going into limb mode and burning fuse 13 on the back. I thought to recheck o ring plug on the bottom if its still leaking or if garage didnt really changed it. I got under car with a lot of effort and found fluid on contacts, so I cleaned with contact cleaner seemed all cleaned, including up the cable flashed with cleaner. Put it all back, plugged battery and it still running in limp mode and still burns fuse 13 on the back. I thought to give a try again with ebay tcm and car started now, but still in limp mode and fuse 13 burned.

You might me right, now next step will be trying changing loom from o ring plug into tcm.

Anyone knows good electrician in London who might be able really find the problem?

ecmexchange

romeovictrbravo has the right idea, wish I could help on electricians in London.