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Hi, can anybody help?, gearbox goes into 'safe mode' when cold but if you switch off and restart engine when warm works fine, changed fluid made no difference, fault code shows No. 39 'no transmission signal output RPM signal' any ideas what causes this fault, thanks
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No mention of age of your Astra, but the most common thing to go wrong is the selector switch on top of the gearbox.
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1.6i 93 on a k plate 55k only, my mums car, thought it might be the selector switch but also wondered if it could be one of the sensors. As you can imagine, because of the age of the car (and my mother) dont want to be throwing good money after bad although the car is in A1 condition and much too good to give up on easily, thanks for your reply dave, does anybody know much about these codes?
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The trouble code is pretty self explanatory. The ECU is having difficulty knowing the speed the output of the transmission - i.e., the speed of the car, and consequently doesn't know when to change gear.
The output speed sensor is, like many speed sensors, just a coil of wire - check the resistance across the terminals when it is giving trouble. The resistance, depending upon exactly which gearbox you have, should be between about 300 Ohms and 700 Ohms - but if there's a fault with the sensor, I'd expect the resistance to be sky high (if you read 710 Ohms, then it's fine, but if you read 7K Ohms, then it isn't!)
Also, before spending any money, check the wiring between the output speed sensor and the ECU - terminals 30 and 31. These wires should make good connection, and should not short to earth anywhere.
If you haven't a multimeter, or don't know anything about wiring, take the car to a good independent, telling them to check this circuit only, and not to fit any parts without your permission - you should be able to get this work done for a reasonable fee. It really could be something as simple as a poor connection or a chafed wire
Number_Cruncher
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thanks number cruncher, will check the connections, also sorced a couple of auto's at local scrappy and know a good auto electrician who may be able to test the sensors so fingers crossed it may not be so bad as first thought. watch this space!
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Top gearbox sensor, I disconected the bottom sensor something completely different happened so obviously working but when I undone the top sensor problem remained the same so assumed this was faulty, changed sensor problem solved, hope this benefits those with similar problem. Thanks to all those who replied.
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cost .....and do you get to it under car or through the linkage please friend?
its knowledge i like............
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The two sensors are easy to get at from under the bonnet, as is the selector switch. I got my sensor from the local scrappy for 'free', just one 10mm bolt to undo and a connector. To read the codes go to vauxhall and pay around £50 or do the same as me and use a paperclip!! see www.topbuzz1.carenthusiasts.co.uk and www.akirwan.freeserve.co.uk/akhow2/diag_no3.rtf, only works on pre 1997 approx models I think. So the cost my friend, about £2 worth of petrol. hope this helps.
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