I have a Voyager 2.8 CRD Executive Automatic which had a fault code of P0605 untill a mechanic cleared it. As far as I can gather looking on this forum is that with this code you should replace the PCM. With this being an expensive item to replace I just wondered what the views of the forum are to the following scenario. The little boxes around the P,N,R,3,L all lit up and as I was driving the auto box by itself started changing from D to 3 and to L, then just straight from D to L. When it did this of course the revs shot up and made me very worried that if I went home at speed I would blow the engine or something. I took it to a transmission specialist (not main dealer) who said there was nothing wrong with the box but something wrong with the electrics. He then proceeded to clear the fault code. I went then to a main dealer who used the diagnostic equipment to say that there was a fault on the wiring to the PCM, the fault code did not appear on the screen because it had been deleted by the first chap that looked at the car. Fortunately I had used Torque OBD on my phone which had picked up the fault code, this I had screen printed just in case I needed it. I showed this to the Dealer, they said they could find no record of the fault code on the vehicle so they recomended rewiring up to the PCM. This they have done and it was better for a couple of days but now it is back with the lights around the boxes again and changing from D to L by itself again. The car is booked in tomorrow to have the PCM changed which is around £550 fitted, my concern is that the problem might not be solved and I will then have spent £825 in total trying to sort out this problem. To be honest the main dealer seems hopeless, so I suppose I don't have much confidence in what they are doing. My question is, does anybody know if there could be anything else that could be causing this problem apart from the PCM.

 

If this helps, the manual states:
TRANSMISSION - EATX

Symptom:
P0605-INTERNAL TCM

When Monitored and Set Condition:
P0605-INTERNAL TCM

When Monitored:
Set Condition: The TCM is reporting internal errors and must be replaced.

POSSIBLE CAUSES
TCM - INTERNAL ERROR

ACTION
Using the schematics as a guide, inspect the wiring and connectors. Repair as necessary. Pay particular attention to all power and ground circuits. If there are no possible causes remaining, view repair.

Repair
Replace the Transmission Control Module per the Service Information.
WITH THE DRBIII PERFORM QUICK LEARN AND REPROGRAM PINION FACTOR.
Perform 41TE TRANSMISSION VERIFICATION TEST - VER 1.