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Vauxhall omega/astra G no speedo fault.(no RPM signal on ecu) simtec 56 ecu code 29

The fault covers SIMTEC 56 ECU's fault code 29 signal input odometer (i.e uk no Speedo signal ) the speedo signal comes from the abs unit to the engine ecu, the volts for this is a maximum 10v this is controlled by the abs unit, ( older vehicles its a relay in fuse box with systems without abs). if the voltage is just 0.1% higher than 10 volts the speedo will so no response when driving, but if you put a load on the system ie lights, radio, indicators the speedo will seem to come to life again, Indicators will make speedo jump up and down. the fault lays down to the alternator, if you check the voltage at the battery with a voltmeter with the engine not running it should say between 11v to 12.5 volts depending on the charge.leave the voltmeter on battery and start engine you will see the volts go up to 14v to 15v. the closer the voltage are to 15v there is the problem any voltage over 14.5 volts is overcharging the system. as the speedo is a 10volt system this will over load it and make it not work. depending on the damage done by overcharging the battery you will need to replace the alternator or the regulator fitted inside the unit and or the battery. to sort this problem out. as this fault is down to the voltage being too high this can damage the cells in the battery, it cooks the cells. I would recommend changing the battery at the same time as replacing the alternator. there are devices that can help stop the alternator from over charging the battery, these are voltage stabilizer. they work by keeping the voltage at a steady voltage I.e not dropping and then going up all the time while using devices in the vehicle, they protect the battery and also your vehicle systems there are loads to choose from. they can help your battery last longer and sometime even improve your fuel economy. the type i would advice is one that fits on the battery terminals. as this way there is no cutting wires or making new connections to fit the unit, most new vehicles have these fitted as standard now. this fault does not relate to no abs signal or mph signal as that fault code is with the abs signals, Vauxhall/opel omega speedo signal come from the pass side front wheel if this sensor fails this fault will appear ( abs light/TC will illuminate and no speedo) Hope this helps you with this fault code 29 to add to also check the blue white wire to the sunroof module. take of the cover for the sunroof, and unplug the connection on the module, then try again just drive the vehicle to see if the speedo moves, if it does then the problem is with the sunroof, the sun roof changes the speedo signal to say there is a drag because it is open.

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Pn, codes, definitions of letters and numbers

I would suspect the speedo head itself as they are prone to get moist inside.

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the speedometer on this car is worked via an electric signal
from the abs system,if the odometer trip has failed it will
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cheers Brian

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I have the same problem with my 2000 v70 glt a not only does the break, abs, and check engine lights come on and the speedometer and odometer don't work but the arrow starts flashing and the vehicle seems to start in high gear! Which of the many speed sensors should i check?

The most common problem is with the ABS control unit. You will most likely have to replace it. It is located under the brake hydraulic unit (not the master cylinder). This part can be purchaced from a Volvo dealer, or sent to one of the many places that repair them. If you choose to fix it yourself, and would like the name of one of the companys that repair them, let me know.

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