Gearbox fault

My Vauxhall Omega has the following pending codes: ‘P0727 engine speed input circuit no signal’ and ‘P1781 ECM actual torque signal malfunction detected’. Both codes are listed under ‘Gearbox fault codes’.

Occasionally, it will take a few seconds to fire up – usually it fires immediately. It then puts the gearbox into safety mode. It can do this with a hot or cold engine. Also, the gearbox sometimes does not change up when it should, but switching to Sport mode rectifies the situation. I replaced the crankshaft sensor to rule that out, but it did not make a difference. Looking on the internet for code ‘P1781’ showed up a gearbox valve block needing replacing, but this was on a Jeep so may not be connected. Melvyn Before diving into possible gearbox-related faults, make sure that your ignition system is up to scratch, since Omegas of your age were susceptible to electrical noise corrupting the gearbox ECU’S data. Only fit recommended spark plugs and check out the HT leads for excessive resistance. Beyond that, check the auto switch on the side of the gearbox, as this can be a problem with an Omega. I replaced the spark plugs with Bosch FR91X Super 4 items, which were the same as the ones I removed, which were in good condition. The Omega has a single long coil pack that bolts onto all four spark plugs – this also appears in good condition. I checked the connector to the gearbox switch – it was clean and had no corrosion – and the switch was replaced about three years ago with a new Vauxhall main dealer part. I have not tested the coil pack. Melvyn A problem with the coil pack would show as misfiring, so you can discount this. You can get gearbox errors when the cam sensor plays up on the 2.2 Omega, and although a cam sensor fault code would be expected as well, a cam sensor fault can generate an engine speed signal instead. So it would be well worth changing/checking/cleaning the cam sensor and its connections. I fitted a new Delphi sensor and then had terrible trouble starting the engine and it showed up a camshaft sensor error code, so I put back the old one. I then tried one from an old Cavalier – it started easily, but was showing an accelerator position error code. I have just fitted another new sensor from a different supplier and that seems fine. Melvyn