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Have you tried changing the gearbox oil? Made a world of difference to mine when I had it, and should only cost a tenner.
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This sounds like the all too common selector switch on top of the gearbox (although as per David Horn's message, an oil change can also solve the problem)
To read out the fault code, you could try the following info.
www.akirwan.freeserve.co.uk/akhow2/diag_no3.rtf (scroll approx half way down the page for the autogearbox info)
If sucessful, report back the code error(s)
btw, a new selector switch will cost you somewhere ITRO £250 to £300. I have seen postings on another forum where someone has managed to strip one down and clean it up, but before going down that route lets confirm what the problem is first.
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Many thanks for the advice. How do i read the codes? I don't have a fault code reader. The problem seems to be worse when the outside temperature is cold. This is why i don't think its the selector switch. I know its an old car but it's only done 50,000 miles and drives like new. It's taxed and mot'd for just under 12 months so would be a waste to scrap it.
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Many thanks for the advice. How do i read the codes?
Follow the instructions from the link I posted. You don't need a code reader, just a paperclip to short out the relevant pins.
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3 things to try before you spend a lot of brass
no1 try the battery off trick for a minute,it cured the same problem i had on a corsa auto a month ago that would only run in 3rd gear and jerked badly into reverse
no 2 apparently the reason it goes into limp home 3rd gear is to protect the box as it thinks the oil is too thick,therefore try letting the car idle for a few minutes prior to setting off and see if this stops the light coming on
no 3 think david horn had it? get the oil changed.
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I would agree with DD on this one, i used to have a Carlton auto with exactly the same problem (only when cold too), and it was the selector switch.
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One other thing - the gearboxes run a different program when cold in order to warm themselves and the engine up faster - it'll hold 1st and 2nd gear for longer. Dunno if this has anything to do with it.
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The fault diagnostic came up with code 47 and 56 which his down shift protection and Selector Switch (Incorrect Signal). I take it an oil change won't work and the selcector switch will have to be either stripped and cleaned or replaced.
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I don't know if there's a more modern way to check this using Tech2, but;
Using Tech1, in the F0 data list, I would check that
1) the transmission input speed is the same as the engine speed, with the transmission in neutral and the engine ticking over - the trouble code 47 is caused when the gearbox shifts down at too high an engine speed. If the gearbox ECU "knows" the correct engine speed, this should never happen.
2) check that the gearbox ECU reports the same selector switch position as seen physically from within the car. i.e., engine off, ignition on, run through all the positions watching the corresponding value in the data list. If you find there are problems here, there are further procedures (stil within the F0 data list) to help make sure it is the switch rather than a simpler (and cheaper) wiring fault.
If you take it to a garage equipped with Tech1, these checks are very quick to do. Even if you end up at a dealer, by limiting them to just doing these checks, you will protect yourself against a hefty diagnosis charge.
Number_Cruncher
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I've dug out a bit of info, hidden in some old notes, which I hope will enable you to check the switch out without too much hassle or expense.
The selector switch has four terminals, A, B, C, and D, and there's a sort of truth table linking the selector position with the switch output.
Terminal Active Inactive
A P,R,3,2 N,D,1
B R,N,D,3 P,2,1
C D,3,2,1 P,R,N
D P,N,3,1 R,D,2
Or, representing this same data in another way;
Position A B C D
P 1 0 0 1
R 1 1 0 0
N 0 1 0 1
D 0 1 1 0
3 1 1 1 1
2 1 0 1 0
1 0 0 1 1
As you can see, only 7 of the available 16 possibilities for four bits are actually valid - the trouble code is set when the ECU detects an in valid code, say 0111.
Looking at the list of valid codes, I think it has been set up rather cleverly, because to go from one valid code to another, you need to change two values, so, if one switch fails, it will be picked up quickly.
Number_Cruncher
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Hi,
I have a 97 (p) LS estate and I found something quite remarkable. If you blow fuse #20 (cig lighter, reverse lamps + heated seats) then the auto warning light comes on and will not go out.
I mainly see the light when the weather is cold and I can remedy the problem by restarting the engine. But if the fuse is blown, it will not go out regardless of how many times you restart.
I have absoulutely no idea why, but its repeatable and consistent. So if your having trouble with your warning light, try reseating fuse number 20 and see if it goes away.
Hope this helps
Graeme
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