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[terry paget]

X84GNB 2.5 petrol V6 estate
Stripping above car for spares, I realised that I did not know where the cam sensor was, never having changed one. I wonder why they are so troublesome on four pot Omegas, and as good as gold on V6 Omegas?

[Andy H]

Good question

My theory is that the ECU software for the 4 cylinder engines is written around the code for the cam sensor. If the cam sensor signal isn't present then it all goes tits up.

The V6 ECU code seems to be written around the crank sensor code. If there is no crank sensor signal the engine won't run at all. The 4 cylinder seems to be able to limp on with a faulty cam or crank sensor IIRC The V6 code doesn't seem to be as buggy as the 4 cylinder code though and doesn't throw up any (as many?) spurious error codes.

Chances are that the V6 crank sensor isn't much more reliable than the 4 cylinder sensor but the ECU doesn't care so we don't know about it...........

[plym ian]

It's punishment for not buying a v6

It's vauxhalls way of making money I suspect

[Kevin Wood]

Probably something subtle about where the sensor is located. Heat, vibration, etc. will all contribute to failure, and I guess they got lucky with the V6 design, and not the 4 pot.

I can't see the ECU software making much odds, although that will determine how it responds to failure (not well on a 4 pot!).

[TheBoy]

Maybe positioning of the sensor (both within sensor itself, and in regard to the point on the cam), maybe better sensitivity.

[chrisgixer]

Seen some that have recovered by removing the iron fillings from the end.

Being magnet based, they attract any metal around, so in the cam belt cover, with a level of fan effect, filings end up on the sensor.

Other than that, it's just poor manufacture. Windings within only need a broken wire, and that's it. Pop.

It's not just omegas. They all fail in the end some more than others. Vag group cars being just as bad. Abs sensor faults often over complicated by pattern parts that just aren't fit for purpose. Whack a genuine one in. Bingo. All fine.

[Andy H]

My understanding is that crank sensors have to produce rapid pulses (36 per crank revolution?) so a simple coil of wire round a magnet works well.

Cam sensors only produce one pulse every other rotation of the crank (every rotation of the camshaft). A coil of wire doesn't produce a fat enough signal to be easy to detect in the ECU so a 'Hall effect sensor' is used instead. The hall effect sensor is manufactured as a microchip with signal processing built in so it can send a cleaned up on/off pulse to the ECU.

It should be easier to manufacture a crank sensor to last the life of the car than it is a Hall effect sensor because the electronics in the Hall effect sensor don't like being held at 85degC. (it took VX/Opel to route the V6 crank sensor cable so close to the exhaust manifold that the cable cooks )

[05omegav6]

V6 cam sensors do fail, but very rare...

Changed one on Joshs estate last year... swapped to another car and fault followed, second hand sensor cured it

[dbug]

Had one go on the 2.6 V6 Estate when we first got it - replaced under warranty, no probs since
Symptoms stalling at low revs - codes showed failed cam sensor.  Dealer fitted new crank sensor (no change) and then new cam sensor (cured).

[terry paget]

Had one go on the 2.6 V6 Estate when we first got it - replaced under warranty, no probs since
Symptoms stalling at low revs - codes showed failed cam sensor.  Dealer fitted new crank sensor (no change) and then new cam sensor (cured).

Similar symptons to 4 cylinder Omegas, stalling at low revs.