No cam signal on a good working circuit P0340

HI guys!

I'm at a loss with this car. It's throwing up a cam sensor circuit fault that I can't fix!

The sensor has a 12v feed coming from a fuse, the sensor ground goes to the ecm, and the signal has a 5v ref (pull down) coming from the ecm.

With the sensor plugged in, and the sensor unbolted from the car, the signal voltage is close to 0v. unplugged from the sensor it reads 5v. I've checked for voltage drops on all wires and they're all good!

The issue with this sensor is there's no signal coming from it when it's bolted to the car.... I can do a bypass on the signal wire by grounding the signal and pulling it down, creating a squarewave, and I can trigger the sensor by passing a piece of metal over it. It's seems there 's an air gap issue between the sensor and the camshaft gear, yet there's nothing out of place!

HELP!!!

What kind of car is it,year,engine?

Does it run but throwing code?

Hi,

It's a Vauxhall (GM) 2.2 GDI engine 2004. It does start but difficult to keep running.

I would check mechanical timing, may be the chain is stretched and the signal happening at the wrong moment aka (out of sync). Check pid on the scanner.

Another thought, can you monitor the signal (when it is in low state ) , while unbolting the sensor? Maybe internal circuits getting distorted under torque. It would be easier to check.

There is NO signal when bolted to the engine. I'm using a labscope! Even if there was a timing issue I should still see a signal.

This car has just had the timing chains done. The issue wasn't there before, so the problem seems to have been created! All wiring checks out good. The fault seems obvious in that it's an air gap issue, but nothing looks out of place.

How about cam sideplay? That will change the gap.

The cams haven't been disturbed. Can't see any sideplay being so excessive to cause this issue, but it's one I didn't think about. Still think I would catch the odd signal in any case.

Is it possible that when mechanical timing is off computer isn't sending voltage on signal wire? Just throwing thoughts.

Voltage is present, even on a crank. It's just not pulling the signal voltage down when bolted to the car and plugged in.

Hey Paul! Good to see you here.
So to be clear, does the signal get pulled down with ferrous material near or away from the sensor?
And is it fixed at 0 or 5 all the time?

Nice job so far bro

Hi Paul!

The signal wire has 5v unplugged. It has around 60mV plugged in. When I place ferrous material near the sensor it pulls it back up to 5v. The original sensor had 763mV on the ground plugged in. Based on that I changed the sensor. I checked the sensor ground and it's less that 100mV with everything switched on (loaded). No drops on the feed either. The car runs but cuts out if you take your foot off the pedal.

I'm not ruling out that I might have made an error installing the new chains, but I don't understand why I'm not getting a signal. It's screaming 'air gap' issue but it really can't be. If anything the gear would be closer if there was an error during assembly.

The transducer I bought needs to go back, as it's faulty. I was looking to use that to confirm a timing issue.

I've had both P0340 and P0341 codes appear at different times. After clearing them one or the other will return.

Sorry, 763mV on the signal when plugged in, not the ground.

I'm not sure if this is a bias voltage used by the PCM to confirm cam crank relationship? I don't no enough about that, but it's now got me thinking!

Can you get an inspection mirror to view the reluctor? How about an image of what that reluctor should look like?
Did you have that gear or reluctor off when you did the chain?

It's not a bias. You proved the working of the circuit with a piece of metal

Hi Paul,

The reluctant is the exhaust cam gear. There's holes cut out the gear that basically triggers the sensor. I'm not sure if you can make the photo out very well. I had to brighten it up using a mobile version of Photoshop.

Paul, you have just inadvertently fixed this car by asking for a photo, and you've no idea how dumb I feel right now!

The photo I sent you was before the chains were replaced. I'm looking at that gear in the photo and it's not the same! I've just put two inlet cams on this thing!I've been sent two inlet gears in the kit! Either that or it is round the wrong way! They both have the same part number stamped on them.

This is an air gap problem because it's the wrong gear!!

As much as I feel like an idiot I'm still happy that I knew how to troubleshoot the sensor and was correct about the air gap!

Go easy on me! lol

Go easy on you? How about some praise brother! You called it out of the gate! Air gap issue. Your testing methods were spot on. Knowing circuit design was key wasn't it? Very nice job Paulie!

I had people telling me it was the ecu. I knew it wasn't, based on logic. It's doing what it should be doing, it's just not doing it when it should be, mechanically. Just goes to prove yet again that you should always compare the new parts to the old. That was a school boy error. I'm getting rusty! At least my troubleshooting is up there!

Thanks again for taking the time!