Grand Voyager 2.8 gearbox in limp mode
I replaced the alternator on this vehicle last week. I'm not sure if this is related but ever since the gearbox has gone into limp mode and is stuck in 2nd. It will still select park, neutral and reverse. I have a p0700 code and a p1468 code. I have changed input and output sensors but this hasn't worked.

 

If your battery reads 13.5 to 13.8volt with engine running, it likely that alternator is not causing your gear-change problem. There is a faint chance the new (or was it second-hand?) alternator is pushing out a lot of "hash" which is impressing itself on the 12volt line and upsetting the autobox microprocessor. This "hash" may appear on the radio (esp. off-station) as a whining noise, which changes pitch with engine revs.

Try strapping another fully charged battery across the main one (be careful polarity is correct) and see if this cures the gear change problem. You might have to be ingenious about driving it with another battery strapped across!

Code P1468 indicates a fault with serial/parallel output drivers (SSPOD) which couild well be a glitchup in the micro. P0700 indicates a transmission control problem, which as Paddy Ashdown might say is a statement of the bleedin' obvious.

The old "disconnect battery -ve for a few minutes" trick might work by applying a hard reset to your autobox micro. Have radiocode to hand if needed.

Something to chew on there, no doubt a contributor may have had exactly your problem after fitting an alternator and will say what is the root cause of problem.

Leedsman.

 

I'm not familiar with the P1438 code, I can't find any reference to it the docs I have either.

On the dashboard, are all the boxes lit around the PRND indicators? If so then it means that the dash cant talk to the gearbox ecu, if the box moves as you select from PRND etc then it means that gearbox ECU is at least running and talking to other systems.

Regards
Richard