Hi All,
can anyone tell me where i can find the vehicle speed sensor on a 2ltr Omega please?
I have an ecu error reporting no signal from vehicle speed sensor but i'm not sure weather the sensor is on the gearbox or on the speedo itself.
Symptoms are inoperative speedo and no Inst/Cons readout on the computer display.
Thanks
Simon.
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The signal may come from the ABS unit which would generate a speed signal from the wheel speed sensors.
Do you have a fault on the ABS at all?
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hi,
thanks for the reply. Yes the ABS light is also on, this came on about a month ago so I had it checked out by vaxhall and they said it was the controller showing a fault then the quoted me megabucks for a new one.
Other than the ABS not working everything else was fine until last week when the engine stalled, when i started it up again I had 3 faults, air mass sensor, air temp sensor and the speedo fault.. I changed ther temp and air mass sensors at the weekend along with the ECU. the speedo still doesn't work! It also reports error numbers 24 (speed sensor no signal) 72 (air temp sensor)and 73 (air mass sensor) the last 2 i know to be good as i changed them at the weekend :(
Help!
Si.
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IIRC, front wheel drive Vauxhalls have the sensor on one of the rear wheel hubs that may in fact share the ABS sensor. Not sure if same applies to RWD though.
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There are two types of ABS setup on Omega's apparently, on the older cars (like mine) there is an ABS sensor on each front wheel and a shared one for the rear wheels... I think!
So you think that the speedo fault may well infact be caused by a faulty ABS sensor? I don't understand how the system is setup really, I also have an old rover SD1 which has a mechanical goody on the gearbox which generates a voltage and passess it on to the speedo to give the readout, i know its probably a bit more modern on the omega but wouldn't it be a similar setup?
thanks
Si
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If you pop the wheel off you should see a toothed wheel (tone wheel) on the back of the hub and a sensor close by - probably tubular meatallic with a rubber boot and wire.
As the toothed wheel passes the sensor a sinewave is generated whose frequency is proportional to the vehicle speed. The sinewave is squared-up inside the ABS ECU to be used by the microprocessor to determine whether it needs to control the braking function. It would also be probable that the ECU will form a concensus of opinion between all sensors to verify the speed.
So, knowing what size wheel / tyre you have on the vehicle, you can determine the speed and distance travelled.
One thing you could look at is the gapping of the sensor from the tone wheel - too far and it will not cause a signal at the ECU. However, I would have thought that the ECU diagnostics would have detected a poorly gapped sensor. Check all three / four with the vehicle jacked up by rotating the wheel / hub. Ensure that there is clearance but not too much - 2mm should be good.
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Going back a bit but my 16v 2Ltr Astra GTE with F20 gearbox had an electrical sender on the top of the gearbox instead of a speedo cable. Mind you it did have the digital dash.
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Hi,
thanks to all who submitted postings to my query! very much appreciated and useful also, especially the ABS stuff! Just for the record, the speed sensor is located on the near side of the gearbox (large diameter bolt body), i took it off and tested it with a ohm meter, no reading... gave it a bash on the worktop, reading... fixed and sorted! The ABS ECU was faulty, a used one from the scrappy (£95 inc VAT) sorted this although it is a fiddly job and make sure all the system is fully bled afterwards, starting with the nearside front and working round clock wise. If aquiring a used one from a breakers try to cut the existing break pipes leaving the unions in tact and a length of pipe protruding, once out flatten the ends of the left over pipes as this will save you some bleeding later as it will help keep most of the fluid in the unit and not ingress air into the system, although its recommended that you give the system a good flush through with new fluid during final bleeding. The other faults registering were Air Mass sensor and Air temp sensor, both in fault according to the ECU, i changed these as a matter of course so not sure if the errors were relating to the speed sensor or just coincidence. All i need to sort now are worn wishbone bushes so if anyone has any handy tips on this job i would be please to hear them as it looks like turning out to be a complete mission... thanks again, Simon :)
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