Camshaft Sensor

[ben penson]

Hi
I have read through some posts on this forum regarding this issue, so it may feel like groundhog day for some, but bear with me.
I have the dreaded Camshaft Position Sensor > Sensor G40 Not a Plausible Signal. This is confirmed by a Seat main dealer.
The fault manifests itself in the usual fashion, by a failed start. Re-cycling the key i the ignition several times has no effect. I have not ODBII kit so unable to reset codes.
The fault has been on the car for some time, both before and after a CAM-belt change, but as the car is running fine, good mpg, no EML and responds to requests for power in the usual manner - plus no worrying noised from the engine i am 99% the CAM-belt is OK (but i will check the teeth!)

The dealer is aware the wiring loom has been worked on in the past. An issue with the glow plug loom meant it was replaced and the new loom spliced into the existing main loom.
The dealer suggests (sic) "to jiggle the wires" and try the ignition again. This works. Like a dream.

My first questions - is sensor part of a pair located in two places? First behind the oil filter (very visible) secondly (possibly the sender unit) located in part of the engine on the driver side between the CAM-belt.

When the engine does not fire from "jiggling the wires" I work my way back to the battery, checking at every stage. Eventually i under the battery tray there are other wires possibly going to the starter motor which when adjusted, appear to allow the car to start.

My second question - could the fault though reported as the camshaft sensor be a break in the cable nearest the starter (or part of the ignition wires) or an issue between the starter and battery or a general break in the cable in this area?
No contact points are loose, simply by "moving" the cables does the engine fire.
This is of particular interest to me. Any thoughts on the wiring would be very welcome.

My final questions is on the 2004 seat leon 1.9tdi ARL, where is the G40 sensor?? So many conflicting suggestions where it is to be found.

Thank you for your time.

 

[Thai-wronghorse]

The sensor is tucked away beneath the cambelt cover and is a right fiddly pig to access and the cable passes through the cambelt back plate.

Sent from my SM-G930F using Tapatalk

 

[ben penson]

Oh great. That sounds like a fun job??
On the off chance the sensor is fine - bearing in mind i have been know where near this item - do you have any thoughts on why specifically the wiring near the battery starter motor when moved/squeezed results in the engine turning over?

Thanks,
Ben

 

[verbal_kint]

Moving a wire and something works when it didn't is undoubtedly a break in the wire...somewhere. When it's a wire in a loom then the task is just a bit tougher but not much.

The likely source is the point of splicing but really could be anywhere.

I would also not ignore that it could be several points of problem including the connections. I would undo and clean all connections first.

Old wiring can go from corrosion, rubbing against something and exposing the inner and then damage.

Then with a multimeter, and ideally with insulation piercing probes, check each wire for continuity, moving each as you do to see if the signal breaks (you may need a 3rd hand ) A similar but better test is to check resistance, high resistance along a wire can indicate a break or corrosion. Just do NOT run those tests an a live circuit!

Happy hunting.

 

[Muttley]

Cam position sensor G40 is below the cam pulley and scans seven teeth on the camshaft sender wheel that is bolted to the back of the cam toothed-belt pulley. You can see it after removing the timing belt upper cover.

The sensor next to the oil filter is G28, the engine speed sensor. A failure of either sensor will stop the engine.

Both G28 and G40 go through the connectors that can be seen behind the oil filter housing. G40 is the one on top, G28 the one below. Worth looking at the state of the contacts in both those connectors.

It would also be a good idea to trace the glow plug harness back to the point where this "splicing in" has been done and look for any damage in that area.