Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
i was wondering could anyone maybe help me with a problem im having with a cam sensor.
Its a 3 wire cam sensor iv tested the ground and thats ok iv tested the power feed which reads 5v and then its the signal wire im unsure of. It reads 5v with KOER and sensor disconnected then with the sensor connected it reads around 2.3v to 2.7v. I dont have a scope but i took the cam sensor out and i had it connected then i put a socket up to the end of the cam sensor to see if the voltage pulled to 0v and it did. But as a side note whenever i get the cam sensor DTC i seem to get a few other DCTs in the brake system and the centeral electrics system and immobilizer system all say ECU disbaled or no signal.
Based on all that im unsure if its a faulty ECU or not.
Standard obd code P0341 i cant remember the code the vw software on the autel maxisys 908p gives as thats my disgnostic tool iv got and i lm at work at the minute so i dont have it with me
Its a VW fox iv attached a few pics of the faults and the vehicle model, ignore the speaker fault thats all sorted but theres the cam fault as initially described and also random other faults which dont make sense
Ok we didn't get the fox stateside so I don't have any information on it. Does the code return right away or short drive? According to Ross tech faulty wiring,faulty sensor, or engine timing can set this code. Being a non us market vehicle I don't have access to timing procedure or known good scope captures of cam/crank correlation . From the tests you've done it sounds as though wiring is good and would suggest sensor is good as well but without a scope we can't verify there aren't any performance issues with the sensor. I would verify engine timing first. If this is a vvt motor we will need to verify vvt is not the cause of this .
Yh i thought you may have had the little problem of it not being a US vehicle, thats what i was thinking that the wiring and sensor do seem good, its not a vvt vehicle. See now i was thinking it might not be a timing problem because i was thinking if it should be a square wave and its a pull down circuit then should it be moving from 5v to 0v on a off as the metal parts on the cam wheel pass the sensor i didnt think it would show a voltage of 2.3 to 2.7?? I thought even if the timing was off the voltage would still show 5v and 0v on and off but obviously it would mean the car is running wrong but the sensor would still be fully functional as it should and thats why i was thinking a faulty ecu with it showing 2.3v to 2.7v and i know its hard to call a bad ecu but do you think the timing could be off? I mean sometimes it can be an extra 2 seconds of crank time before the engine starts and the code usually only comes back after a drive. But also like you say one of my problems is i dont have a scope either.
If it's non vvt you should be able to check timing marks to verify engine timing and that's where I would start. I think we can rule out the pcm being the problem with the tests you done. Also if the code doesn't come back immediately that also suggest pcm and wiring are good without a scope it's hard to verify but I think this is going to come down to a cam sensor . Definitely check timing first though
You got 2.5 volts while engine was running correct? If you think of it as a high speed pulse or duty cycled at 50% for ease of understnading you will read 1/2 peak voltage on a low speed volt meter so let's use a purge solenoid for example the pcm controls it on a 12v duty cycle and if duty cycle while testing is at 25% we will see 1/4 of are voltage Valentine running approx 13.5 volts so are reading on a low speed meter would be 3.3v give or take a few decimal points when viewed on a scope you will see on and off time with 0v to 12v (or 13.5) and the length of on time compared to off time in 1 cycle will tell us what the duty cycle is.
Iv not had time to check the timing yet in this vw fox but 1 thing i have noticed is it will let me view live data on all systems apart from the ecm it just says function not supported and it still keeps throwing them 3 faults
Hi Sam
I am new to the forum but an avid follower of Paul and his you tube videos.
I am a Certified Bosch Mastertech in the UK so more familiar with the European and Asian vehicles.
Back to your VW Fox.
From my experience P0340 is set when there is no signal from the CMP and P0341 is set when there is a signal but the PCM does not like it - timing etc.....
You could prove this by disconnecting your CMP or cutting the Signal wire with a view to promoting changes in the DTC's you get.
If that is 0-5v Hall Effect Sensor then it is no surprise that you are reading 2.5v with a DMM - It is taking an average ?? !! Furthermore, is that 2.5v backprobed at the PCM where the signal needs to be ?? or at the CMP Sensor ?
If you let me have the Year and Engine Code I will look up some data that may help you.
However, if the timing pins up ok then I do not see how you can proceed with this diagnosis without a good oscilloscope ! ?
I want to focus on the signal circuit for a minute.
With the key on and cam sensor unplugged, what does the signal wire read? First, at the sensor and if it is only 2.x volts at the sensor, please measure the same wire at the PCM and compare.
Hi shooter, thanks for the reply, yh its is reading 2.5 at the cmp backprobed. Ill check the signal at the ecu. The make and model is a VW fox 1.2 56plate engine code BMD.
So with the key on sensor unplugged the signal wire reads 5v at the cmp backprobed. Also here is a wiring diagram of this ciruit, the cmp is the one in red and the crank is the one on the right.
So its been a long time since my last attempt at solving this problem, i still havent verified the timing yet but a few new things to note....
I tested the resistance of the singal and power wires from piercing each wire at the sensor and piercing the wires at the ecu and the resistance for both the signal and power was a little erractic it was reading 1.4ohms 1.6ohms 12 ohms 52ohms just basically random numbers so sometimes it would settle at 1.4 and then after a few seconds go erratic again.
Another thing is when i unplug the cam sensor it doesnt seem to make a difference to the engine also it doesnt throw a check engine light.
Topic Author
