MIL light on - code P0340

[rich r]

At the weekend I went to start the engine (Jan 2004 Vectra 1.8), and it just turned on the starter but didn't fire. Switched off and tried again, same thing. third time it fired up and ran normally - but with the MIL light on.

Got it booked into a local garage and they said it was code P0340- cam sensor. So they replaced the sensor (genuine GM one), deleted the code and the car has been fine all week.

Until last night when it did the same again. When I got home, I did the brake/accelerator down, ignition on/off routine to get it to flash the fault code - yep, P0340 again.

Now I've done a bit of searching on here (and the Astra and Vectra B forums) and found that the code can also be caused by dirty connectors on the sensor, a slack timing belt or a flat battery.

Any suggestions as to what's most likely? The car had a new cambelt a month ago, but ran fine for 3 weeks with no faults before the first light came on. Then it's been almost a week again.

[rich r]

Solved it

Yesterday the car wouldn't start - so I took the battery out, it showed as being pretty flat (not too low for the electrics, but too low for the starter). So I charged it up all day and refitted it when it was completed.

Car started first time - MIL light and fault code still present (the battery had been disconnected for about 20 hours by this point). However, when I started it again later today, the MIL light has gone off.

So it would appear that the cam sensor is probably perfectly fine, it was just a low battery causing the fault. And the ECU has cleared the fault code itself now the voltage is high enough for the sensor to be giving signals in range.