Cam Position Sensor code wont clear. Wont start. New motor. going crazy

[iamshayan]

hey guys
I'm really confused. I just did a motor swap and I got to 800km on the break in, still havent hit more than 5 psi of boost, still getting used to her.

.... but now she wont start. I keep getting this cam position sensor code - Implausible signal.

I checked the wires and they seemed pretty chewed. So I cut the wires and spliced in a fuel rail harness with one i got from the wreckers.

Voltage checks out the whole way though, Pins 1 and 3 on the CPS plug read 4.9V at key in the accessory position as per the bentley.
Even the Cam chain tensioner shows upwards of 7v at ACC.

I thought this would fix my problem. but Still nothing.

So I have my old motor sitting here and I figure what the hey, why not swap the CPS's and see if that makes a difference... Still nothing!


When it does finally fire after numerous cranks, vacuum sits at 18inhg as if I have a vac leak and runs like shit.
So I once over'd all my vac lines and tightened all my intercooler couplings a little more. Still no help.

I also have an oil pressure sender for my VEI/podi gauge that I just installed not to long ago. It reads 30psi at warm idle. Never any less. and shoots past 99 up around 5k rpm this seems to high imo. Is this regular or am I crazy.
Whats goin on here. (using 5w30 non synth as a break in oil for a bit before switching to 5w40 full synth)

For the record its a
1.8t with brand new forged rods, new bearings and rings, new oil pump, head gasket, timing pump and water belt, gt2871 eliminator, port and polished exhaust manifold, awe fmic, full exhaust, 550 injectors, meth & revo 3.

Been wrenching all day trying to figure it out, now I'm just frustrated and my back hurts and I've given up and come inside to complain and ask for help.
any info pointing me in the right direction would be most appreciated.

[jubei4769]

-18 for vacuum isnt bad and wouldnt cause the car not to run.

my car at warm idle the oil pressure is usually around 31-33 and the only time i see 99 is in the morning on the first start up but then it drops down as the car warms up.

not to sure about the cam position sensor error as im still learning these cars myself. ill try looking in my bentley and see if it says anything

heres a video of mine today at idle

[hanzy]

Check your timing(belt and chain)

Those CMP sensors rarely fail.

Also MVB 90(maybe 91 I forget)-94 will show you a few different cam timing blocks.

Check those out.

Make sure your cct is working by watching requested and actual.

[iamshayan]

Check your timing(belt and chain)

Those CMP sensors rarely fail.

I guess I'll grab a gasket set, cam chain tensioner, valve cover, half moon etc. and inspect that stuff, because the timing belt was on point when I put the motor in, I know that for sure

[MikTip]

Is that the correct trigger wheel on the cam?

[iamshayan]

Is that the correct trigger wheel on the cam?

I think so. I'll go check my old motor to make sure. It has four openings.

[hanzy]

Try checking those blocks first.

May prevent you from having to disassemble anything.

[iamshayan]

Try checking those blocks first.

May prevent you from having to disassemble anything.

I checked 90 and 94 they both say cam control off . OFF , 0.0cf Test OFF
I dont want to drive the car and log them as I dont think it would be safe with my AFR's all over the place.

Right now I checked the trigger wheels. They are identical. I'm really stumped. I called the shop that built the engine for me and they're saying that its my ecu. and my ecu is fucked.
I dont want to hear it. It worked fine with this setup before. Now its a nightmere

[jubei4769]

water in your ecu? didnt it rain a little while your hood was off

[Bische]

What is the code you are getting? Did this suddenly happen or has it been there since you swapped the motor?

The intake cam may be 1tooth off, common mistake as the timing mark on the intake cam is between two rollers.

[Siggiepop]

oh noes

[iamshayan]

water in your ecu? didnt it rain a little while your hood was off

no I beat the rain. Made it to the garage before it happened. worth a shot though, gonna pull the cover off and take a look see.

What is the code you are getting? Did this suddenly happen or has it been there since you swapped the motor?

The intake cam may be 1tooth off, common mistake as the timing mark on the intake cam is between two rollers.

I didnt even time it, the shop did. It wasn't present when I started the car It appeared magically.
the code is P0341 http://wiki.ross-tech.com/wiki/index...5/P0341/000833 again, My wires were chewed I replaced the harness, I'm getting 4.9V at the CPS ( as per THIS link)do you think its possible that the tensioner jumped a tooth!? I have a new one on my old motor that's not even 3 months old. I made sure to count 16 teeth between them on that one, but I havent opened the valve cover on my new motor since I got it. (I don't have gaskets.) Do you think I should get the gaskets and pull it apart?

oh noes

[Seerlah]

I'm voting for something is off on your timing.

Also I see over 100psi all the time. But I boost a lot. I'll post a video later where you can see my gauges.

[travrach]

You mentioned Pins 1&3, what about 2?
Key on-Pin 2 to ground should be 12v.

[jubei4769]

I'm voting for something is off on your timing.

Also I see over 100psi all the time. But I boost a lot. I'll post a video later where you can see my gauges.

ive hit 99 then it goes to hi, just think you need to change the high setting on the gauge

[iamshayan]

You mentioned Pins 1&3, what about 2?
Key on-Pin 2 to ground should be 12v.

pin 2-3 is 10.90v and pin 1-3 is 5.04v today.
Battery + and - are 12.80v so I guess I'm losing a volt? just one? is that really bad?

[AudiA4_20T]

dude your timing belt is off. It looked good when you ran the motor over by hand but jumped one tooth. I've seen it a bunch of times. Also, it's almost NEVER the ECU with these cars. The ECU thing is a common Diag for other cars, but rarely is the ECU the culprit in the B6.

[iamshayan]

dude your timing belt is off. It looked good when you ran the motor over by hand but jumped one tooth. I've seen it a bunch of times. Also, it's almost NEVER the ECU with these cars. The ECU thing is a common Diag for other cars, but rarely is the ECU the culprit in the B6.

Front end comes off again now? I didnt even time it. aghh.
so once the front end is off I just find tdc on the crank and then pull the belt, and adjust the cam back to line up??

[rocky.ca]

just pull the engine back out and give it to me for $1 :)

[travrach]

pin 2-3 is 10.90v and pin 1-3 is 5.04v today.
Battery + and - are 12.80v so I guess I'm losing a volt? just one? is that really bad?

Hmm, lets check the ground side by it self,please reverify battery voltage at battery, still 12.80? OK then go Pin 3 to the battery +, what do you have?

Front end comes off again now? I didnt even time it. aghh.
so once the front end is off I just find tdc on the crank and then pull the belt, and adjust the cam back to line up??

No, not whole front end, we hope.. You can pull top cover and line up harmonic balancer mark with lower cover mark.

[iamshayan]

Hmm, lets check the ground side by it self,please reverify battery voltage at battery, still 12.80? OK then go Pin 3 to the battery +, what do you have?


No, not whole front end, we hope.. You can pull top cover and line up harmonic balancer mark with lower cover mark.

will check that right now.
no mark on ballancer, Used the one off my old motor.
guess I'll go buy coolant, good thing I didnt get my ac charged yet.

[travrach]

No mark???
Pic thanks to walky..

[AudiA4_20T]

will check that right now.
no mark on ballancer, Used the one off my old motor.
guess I'll go buy coolant, good thing I didnt get my ac charged yet.

Right... so you re-wired a whole piece of your harness to fix an issue when you can't even check timing?

[iamshayan]

Right... so you re-wired a whole piece of your harness to fix an issue when you can't even check timing?

to be honest I didnt want to deal with timing thats why I had the shop time it and do everything so it was ready to swap in. I just cracked it over by hand and lined up the cam shaft. I cant find the mark on the tbelt cover but found the one on the dampener.

[travrach]

^Ok, no problem, pull plug #1 one out, the one closest to the t-belt. Put long screw driver in hole, and turn over till cam is lined up again and screw stops moving up and down for a sec, thats top dead center. Did you ever get to verify post #20, ground side double check?

[AudiA4_20T]

looks a tooth off to the left

[iamshayan]

okay I got some more stuff off.

here is a closer picture

^Ok, no problem, pull plug #1 one out, the one closest to the t-belt. Put long screw driver in hole, and turn over till cam is lined up again and screw stops moving up and down for a sec, thats top dead center. Did you ever get to verify post #20, ground side double check?

when i test cps ground and bat + it shows regular battery voltage
I think I can see the timing belt mark on the crank If I line that up. what are the next steps.
Removing the manual tensioner?

anyway I can do it without the tool in this video

[travrach]

Well I still have concerns about that 10.90 volts when it should be battery voltage. But let's continue verifying timing marks.
Let's not worry about taking it all apart till we are certain the marks are off. Next step is do what I mentioned above with spark plug.

[victimdumper]

anyway I can do it without the tool in this video

you *may* be able to get away using c-clip pliers if they are beefy enough.

beefy.

[evo_ski]

Based on the pic it looks like I agree with the others that have said timing looks a tooth off.

[iamshayan]

Upon closer inspection I didnt have the cam gear all the way lined up. They are both on point. I'll post pictures in a sec. Just running to the store.

Sent from my SGH-I747M using Tapatalk 2

[old guy]

I don't know what your problem is but I can tell you what it isn't. Your non-start is not coming from the cam position sensor or from being 1 tooth off on the timing belt. You can completely unplug the cam position sensor and the car will start. It might take several tries but it will start. Once it starts it will run normally. Being 1 tooth off also will not prevent the motor from starting. It may be down on power or run hotter depending upon which direction it's off but the car will still start and run.

You need to look elsewhere.

[diagnosticator]

The voltage is to low between terminal 2 and 3. Either there is a high resistance connection in the wiring harness, or there is a bad ground for the ECU. The DTC P0341, is regarding the output signal voltage of the Cam Position Sensor is outside acceptable tolerances, being "Implausible". The low voltage between #2 and #3 is consistent with the DTC P0341. This means there is an out of specification G40 output signal. This DTC does not have anything to do the cam position, it is only a sensor output signal fault. Without good cam position information, (or believable information,) the ECU cannot determine where each cylinder is at in the 4 stroke cycle, and therefore cannot determine when to open the fuel injectors for each cylinder or when to fire the ignition spark for each cylinder in the firing order. Consequently, during start up, there is no fuel and no ignition, causing the no start condition. Depending on the unique situation on your car, the ECU may be able to eventually use other information to determine what cylinders are doing in the 4 stroke cycle, and once that happens, the engine can start up, after a long cranking period.

The problem with the voltage supply, and more likely, a problem with the circuit wire from the sensor back to the ECU, must be checked for excessively high resistance, measured between the sensor harness connector, and the ECU harness connector, and/or any low or high resistance continuity to chassis ground, from both ends of the signal return wire, aka a short in the signal return wire to the ECU. Both a high resistance connection and a short circuit fault in the signal return or power supply wires will result in the low terminal voltage measured.

BTW, in the pics shown, if the crankshaft is at true TDC, then the exhaust cam drive timing belt sprocket is correctly aligned with the timing mark on the head.

I agree with "old guy" explaining why the problem is not a cam timing related issue. That is the same point I was trying to relate using different parameters.

[old guy]

As previously stated you do not need a functioning cam position sensor to start your motor. Before I made my post above I went out in the driveway and unplugged mine. The motor started on the first try. Basically you have a 50/50 chance of it starting since the ECM will use the crank position sensor without a cam position sensor signal present.

Look elsewhere.

[diagnosticator]

As previously stated you do not need a functioning cam position sensor to start your motor. Before I made my post above I went out in the driveway and unplugged mine. The motor started on the first try. Basically you have a 50/50 chance of it starting since the ECM will use the crank position sensor without a cam position sensor signal present.

Look elsewhere.

Correct. Without the cam position signal, the ECU must use other information to determine each cylinder's cycle stroke for synchronizing fuel injection and spark. Depending on the circumstances unique to each failure, the cranking delay may be unnoticeably short, or very long.

[vvenom800tt]

I have this same problem, just replaced the sensor and still the CEL comes back.

[walky_talky20]

Correct. Without the cam position signal, the ECU must use other information to determine each cylinder's cycle stroke for synchronizing fuel injection and spark. Depending on the circumstances unique to each failure, the cranking delay may be unnoticeably short, or very long.

In the case of a missing G40 signal, cranking duration has no bearing on whether it will start or not. Without the G40 signal, the ECU makes 1 guess per cranking attempt. It is either correct, or 180 degrees out. If the guess is wrong, holding the starter on longer will not produce a successful start (but may produce some backfiring). You must turn the key off and back on for it to guess again. You still have spark and fuel on every attempt, it just may be 180 degrees out of synch. In my experience (although not having scoped anything) the ECU seems to "guess" exactly the same every time. Whether the guess is correct or incorrect is entirely determined by the position of the camshaft at the moment the key is turned on.

EDIT: As per diagnosticator, the behavior I described above is not accurate for ME 7.5 ECU's, whose G40 error correction logic differs as compared to ME7.

[iamshayan]

Hey guys, okay, I'm back at it again today.

I read what you guys wrote about the cps not causing the shitty idle so I decided to try and track it down. I'm retracing my steps removing anything that may be different now compared to when it was working.

So far I've removed my oil pressure sender, replaced the screw in the test port and tightened it.

Then I removed my meth hose as I noticed I went through half a tank of meth on the break in without ever activating meth, Meaning its been siphoning. Which is really strange because it never used to happen and I have the solenoid to prevent siphoning.

So I tried for a bit to get it started, it eventually worked and it seems to idle much better now.
although I have no idea of oil pressure readings anymore lol.

So now I really need to figure out this CPS code because it still wont clear.
I pulled my ECU box off and looked inside. It seems almost like kind of damp but its hard to tell, there is a crack in the cover box with some "rust like colour" on the foam inside
pics -



This did all occur when it started raining and I left my car outside. *hood on!*
on a side note why doesnt my car realize when the hood is closed anymore. it always flashes open on my dis.

[walky_talky20]

While you're at the ECU, I would check resistance between the cam position sensor connector terminals and the ECU connector.

You verified belt timing to be perfect, right? I'd like to see you also check the chain timing.

[iamshayan]

While you're at the ECU, I would check resistance between the cam position sensor connector terminals and the ECU connector.

You verified belt timing to be perfect, right? I'd like to see you also check the chain timing.

Yeah I'm just looking up what pins they could be.
correct, I verified belt timing to be on point.
I will pull the valve cover now, I don't have gaskets/ think anywhere is open today. Should be safe to re-use them temporarily right?

Thanks for all the help guys. Really appreciate it.