Not shifting into top gear on auto box

[Flarris]

I made a post a few days back about a 3.0 KZN130 auto not going into top gear and hovering around the 3000rpm mark more often than is healthy; previously it was noted that the most likely cause of this was simply needing a fluid change / service, and possibly filter change. There was a response to a thread by someone else relating to a similar problem, (and now I can't remember whose thread it was)-trying to find out because that individual mentioned one other possible cause, that I can't recall. Not a relay I don't think, but an electrical as opposed to mechanical problem? Anyone got any ideas please other than the obvious sump-dropping etc, thanks

[IanB2]

Is it not going into 3rd, or not going into OD? If OD, it could be purely electrical.

[TonyN]

This is normally the ECU, sometimes the shift solonoids.

The Gearbox fault codes normally get solonoid faults reliably.

Speed or TPS sensors also cause problems, but all should be picked up by the Diagnostics.

Unplug the gearbox and try it manually, there is a black 3 wire plug on the passenger side of the gearbox, going into the sump area from above.

Shifting on the stick you should get L, 2 and O/D, this will prove the gearbox is mechanically fine. (You won't get D with the gearbox unplugged, this is electronically selected only.)

[Flarris]

Thats excellent advice thanks I will check