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[emboli]

Hi

I've posted another thread regarding the issues i've been having with my GC 2.7 CRD - After having a good look at things i found the transmission connector was leaking. So i've now replace this, and done a full fluid replacement; rather horrid. The MIL hasn't cleared, and i think it's still in electronic limp home mode, which i understand has to be reset. So is there any little tricks or tips on resetting it? I've tried disconnecting the battery, but no luck. Or is it a trip to the main dealer?

Cheers for now.

[isle of man]

Main Dealer fix!!

But they will want to do a short test first, the reprograms will be another 45 minutes, time to bite the pillow my good man.

[jay140285]

I reset my mother in laws using a hand held ODBII scanner after replacing the TCM,

got to be cheaper than a dealer .

[Lukemagnum]

The limp mode is a default programme in an ECM when it can't make sense of certain inputs, allowing you to keep mobile at limited power. The fault code then remains in the ECM for later diagnosis.

Of all the engine management systems I've worked on, even my own GC, once the fault has been rectified (either by replacing a part or the fault clearing in the case of intermittent faults) the limp home setting clears when you switch off and allows you drive normally.

I know that Jeep/Chrysler have some strange ways of doing things, but I think it unlikely that they would do this differently.

It looks like your fault may still be present, for the limp mode to remain.

BTW dissing the battery, shorting the leads, so called discharging the capacitors in a module will not clear the codes. The codes are stored in an electronically programmed memory and will stay there forever until reprogrammed, similar to a memory card in a camera.

[emboli]

So i had my heap in to the garage yesterday for the TCM to be reset, and they couldn't access it with the star machine they had (merc transmission garage). So is it possible to reset the TCM without it being in the car? i.e. is it possible to send it off to be reset - if not I'm only left with a 40 mile drive stuck in second. I guess as long as i don't hammer it, things will be ok - just take rather a long time.

Re comments about limp home will clear when fault resolved - this is true to a point, i believe this is hydraulic limp home. However, if it enters electronic limp home, it has to be cleared electronically.

[Mike Pavelin]

You need a Chrysler DRBIII To access the TCM on a 2.7

[isle of man]

You need a Chrysler DRBIII To access the TCM on a 2.7

I concure..

Star would never communicate with it.

[Lukemagnum]

There’s no such thing as a hydraulic or mechanical limp mode, it’s not like the good old days when you could drive home with a lumpy engine firing on 3 cylinders because a spark plug has gone down. The limp mode itself is not a fault but a set programme to stop you being stranded at the roadside should the electronics detect that something is not right.

The TCM (Transmission Controller) can sense the fault whether it’s electrical or mechanical from the inputs it receives from the autobox and registers it as a code in its memory, It then flags up a P0700 fault in the PCM (Powertrain Controller) to inform it that a fault has registered.  You can bring up and reset the PCM codes with a basic scanner but as Mike has stated you need DRB111 to access the gearbox controller and that is where the specific code is that you need to tell you what’s wrong.

That gearbox was also used in Mercs, Porsches and Jags but the TCM’s are different, so you can’t just go along to a Merc specialist and expect his equipment to access your Jeep controller.

[emboli]

From speaking to the garage i took it to, they have managed to reset a number of jeep TCM's in the past; but it's never simple. So its off to find a Chrysler garage it seems. Thanks for the comment and help; although it would be good to understand if this can be achieved when the TCM is not attached to the device.

My comments regarding the two types of limp home mode perhaps have not been articulated clearly, but are correct (as per service / workshop manual). There are two forms of limp home mode - a temporary lock until the ignition is turned off, which resets leaving a P700 code and associated TCM error code, but the TCM can trigger a semi-permanent limp home mode. The two types i have read elsewhere as hydraulic and electronic (rightly or wrongly i have no idea) the latter needing the TCM to be reset (other threads have suggested that this is why some have replaced the TCM rather than reset).

[isle of man]

If you are a gambling type I would say 70% it's the valve body, these are available as exchange units and are about £700gbp.