Hello dear forum members and greetings from Norway where its 20 degrees below zero!

I have had a lot of use of this forum as a "passive" member, which have solved several problems I've had with my Omega.

Now, however, I have a problem where I've come to a dead end after reading the forum all evening and spending the last week trying to fix the car. I hope with all my heart that some of you with all your knowledge could shed some light on how to proceed to solve the problem.

This is the case:
The car is a 1996 Omega Estate 2,5 Auto. About a month ago I replaced the AR25 gearbox with an AR35 gearbox, from a newer donor car. After the replacement, the car had new life to it, it ran better and geared a lot smoother.

This past week the gearbox suddenly went into limp mode (stuck in third gear while in drive), with no warning light or anything. I can gear manually to 1st and 2nd gear but in 'Drive' its always stuck in third gear.

To solve the problem, I started with thoroughly cleaning all the contacts on the gearbox (I have just had the entire underside of the car sprayed with oil to stop rust, and there's been a lot of snow) so I thought there was a bad connection. This didn't help.

After reading more on this forum, my guess was the selector switch. The selector switch looked really bad inside so I decided to replace it with the selector switch from the old AR25-gearbox which used to work nicely and also looked nice inside. This didn't help either..

I have no problems with the LED's in the selector inside the car, they all work like they should.

I also have a cheap "tech2" diagnostic tool, Op-com/Lonelec. When I first tried, I managed to connect to the gear box and there was a lot of error codes (unfortunately I didn't write them down. I cleared all the error codes, but one remained: "Power relay voltage low".

After that, I haven't been able to connect to the gearbox with the diagnostic tool. Today, I went to a friend of a friend that works in an Opel-dealer, and he tried to connect with both TECH2 and TECH1 but he was also unable to connect to the gearbox.

So now I'm pretty clueless where to look next. I don't have a clue where the relay's are, and the Opel-guy was too busy to provide me with any more assistance or wiring diagrams.

Does anybody have any tip on what to check for? I feel a bit desperate right now, I spent so many hours upgrading the car and now this happens.

Thank you for reading and I'm very thankful for every tip!

Yes TIS could probably be useful.

Oh, and by the way, the gearbox oil and filter has been changed and the level seems fine.

Also, the car ALWAYS starts, so I don't think it is the cam shaft sensor. The cheap code reader doesn't show any error codes on the engine either..

Any suggestions will be deeply appreiciated!

Kneepad wrote on 23. Dec 2010 at 12:15:

Def worth checking.

Went down to the parking garage here at work and put the car in drive. Pressed the snow mode button several times but the car still started in 3rd gear and sport function wouldn't work.

Didn't try to disconnect the whole thing, should I perhaps try that? Wierd that the diagnostic tools (both mine and at the dealer) can't connect to the gearbox?

Thanks again!

Have you checked the selector contact switch? Maybe on refitting the new gear -box the alighnment is slightly off.

I'm just about to order a new gearbox ECU. Pretty expensive, but it's cheaper than leaving the car with the dealer (£150 pr hour).

Any last ideas before I place the order?
Thanks,

PDK1953 wrote on 24. Dec 2010 at 09:14:


Thanks a lot! I'll definately look in to that. Yeah, looks like its really sensitive.

I have a friend with the same car, maybe I can talk him into "borrowing" the sensor to me for testing purposes.

I'll some time reading about this throttle potentiometer now.

Remo wrote on 24. Dec 2010 at 09:20:

Borrowing parts from another known good, is your best bet. Very handy actually. I suppose your first task is to repair communication to the box ecu. If a reader can't see it then maybe the box can't either, hence limp mode.
Theory behind snow mode error is that that function uses 3rd gear for gentle pull away in snow, which is the same as limp mode using third. Thing is pressing sport mode should over ride it, snow mode button is not lit at the time, and bothe sport and snow modes are unresponsive. Gear selector lights are correct. So it's in limp mode it seems to me.

Further diagnosis is difficult tbh, you need one of the admins on here with tech 2 experience. Markdtm, TheBoy, or Kevin Wood. Sugest a pm to the nearest one to you with a link to this thread.