JoeBra

Registered User
Hi guys need some expert advice been struggling with this for weeks and dont know where to go next.

Story starts that a bought a 2005 a5 2.0 tdo blb (140) with what I was told needed a turbo.
Got it home to find that she needed more than a turbo, the head was away and she was pressuring the water enough to cause a fountain out the open water bottle. I could also hear the chain on the balance shafts that I read so much about.
Decided that the engine would cost too much to repair and bought a passat BKP (140) to swap the engine into. picked up the passat and drove it 280 miles home. Good engine driving well.

So both cars still starting I remove both engines and build the Passat engine into a A4 engine (brackets sump oil pickup rocker cover auxiliaries and there mounts) and while I was at the replaced the hex drive for the oil pump. new clutch etc
Used the A4 injectors and injector loom as they are different.

Fitted engine and she wouldnt start and checked VCDS. No faults that should stop her starting but live data not showing engine speed and the rev counter doesnt move when cranking.

Found out the crank pick up wheel also does crank position and needs fitted with a special tool to ensure its at TDC so borrowed 1 of these and fitted a new crank seal and changed from passat crank sensor which had been working with the a4 crank sensor just in case the passat 1 was different.

Rebuilt engine and refitted it but still the same thing. she turns over no problems but doesnt even sound like shes trying to start (no fuel) still no crank signal checked the plug on the crank sensor and it has a GND 5v and a 1.4v with and without the sensor connected is this right?
Probing the signal wire while cranking I couldnt get a signal out. Bought a new sensor and tested it on the bench and cant get a signal out of it either I tested it by moving the old pickup ring in front of the sensor with 5v applied and connected to a oscilloscope.

On VCDS if I look at measuring block i think it was 52 it a shows crank and cam speed and a sync value. the cam speed goes straight up and the crank remains at 0 then after a few seconds of cranking it goes to up but then the cam goes to 0 and the sync value goes up. I cant remember exact values right now but I can get them.

On a happier note I opened the headlights and removed the orange lens and fitted projectors that I think look very good. I'll post photos when I get them refitted.
 

JoeBra

Registered User
I have included a video of VCDS with the crank and cam speeds and a photo of the fault code.
Sorry for the poor quality had to use the front facing camera on my phone
 

Attachments

  • IMG_1798[1].JPG
    IMG_1798[1].JPG
    234 KB · Views: 604

carlcall

Well-Known Member
VCDS Map User
After a quick look on the RossTech website I found this that maybe helpful to you.


17036/P0652/001618 - Sensor Reference Voltage B: Too Low

Possible Causes
  • Wiring/Connectors from/to Intake Manifold Pressure Sensor (G31) faulty
  • Intake Manifold Pressure Sensor (G31) faulty
  • Engine Control Module faulty
Possible Solutions
  • Check Wiring/Connectors from/to Intake Manifold Pressure Sensor (G31)
  • Check/Replace Intake Manifold Pressure Sensor (G31)
  • Replace Engine Control Module
Special Notes
  • When found in 1.9l TDI (BEW):
    • Check Atmospheric Pressure (MVB 010.2) and Intake Manifold Pressure Sensor (MVB 010.3). Compare both Values with Engine OFF, the Tolerance should be +/- 50 mbar.
    • Check Variable Nozzle Turbocharger (VNT). Specifically, check the electronic actuator position sensor G500 , including unplugging it for testing.
  • When found in other engines:
    • Check the factory repair manual since this fault can point to problems with several different sensors.
    • Specifically in the BLB engine, faulty MAF wiring can trigger it.
 

JoeBra

Registered User
    • Specifically in the BLB engine, faulty MAF wiring can trigger it.

Thanks for the reply. I had read that too, the bit that applies mostly to me is the BLB bit for the MAF wiring but I think it should still start with this fault.
I believe it to be something to do with the crank sensor but I dont have another b7 a4 2.0tdi to compare crank readings and measurements to see if im right. If im not right I could be wasting alot of time looking in the wrong location.
I was hoping someone on here has measured their crank sensor before.
 

carlcall

Well-Known Member
VCDS Map User
I maybe able to have a look for you later today if that's any help?


Sent from my iPhone using Tapatalk
 

JoeBra

Registered User
Yea thanks a lot would be great if you got a chance, Ive not been on in a while cause I've not been back to the car. Dreading working on it as it just doesnt seem to want to go well for me
 

carlcall

Well-Known Member
VCDS Map User
Send me a PM to remind me Joe as it absolutely persisting it down at the moment


Sent from my iPad using Tapatalk
 

JoeBra

Registered User
Hi so I've not got any further with this I've not been able to look at it much. And had to waste some of that time removing the sump again. Dont ask lol.
I am planning on going back out to it this week with new injector bolts just to rule that out and was think that when I'm there I could double check all the engine loom connectors are in the right place. Does anyone have a diagram showing where the connectors all connect or would anyone be able to check on their car and do me a quick list or diagram
 

carlcall

Well-Known Member
VCDS Map User
@JoeBra maybe a silly question as in all honesty I'm not sure if it would need doing but.....

When you changed the engine over did you run the fuel pump via VCDS to purge all the lines? Just a thought that's all!
 

JoeBra

Registered User
not a silly question at all. It was suggested to me near the start by a friend and I did try it at least 3 times
 

JoeBra

Registered User
Seen on another thread that some cars have a relay fault that stops the ecu powering up.
A sign of this is the glow plug light not coming on when you turn the key. This isnt the problem with mine as the glow plug light does work. we tried a tow start and the revometer didnt move so has to be a sensor/ecu/wiring fault.

I now have access to another car to check the differences. fingers crossed
 

JoeBra

Registered User
Well guys success.

I'll write up the shortened solution for anyone else with a similar problem. and include the crank sensor values that I could never find online.
Because the problem seemed crank sensor related as the revometer did nothing during crank and the live data doesn't show proper data as shown in the video previous I looked straight at the crank sensor on the running car to find
Green with white tracer - 5v power
Blue - 0-5v signal
black - 0v ground

Compared with the none starting car
Green with white tracer - 1.6v
Blue - 5v
black - 0v

Obviously this is completely wrong and I thought it could be damage to the loom. I opened the ecu cover (removed anti tamper locks from ecu not sure how best to do this but I used a grinder.) from here I cut the wires and tested them again and the signal seemed to be coming from the ECU.
I jumped to faulty ECU and swapped it with the running car to confirm (again more grinding) but the ECU from the none running car started the running car briefly before the immobilizer kicks in. Revs to be seen.
Not a faulty ECU - now what lol (solder cranks sensor wires)

Decided there must be something different about the running car loom or sensor causing the ECU to act like this while connected and to pull off 1 sensor at a time to check the Green with white tracer - 5v power to see if it jumps to 5v and compare each wire in each plug with those in the running car.

BINGO - EGR unplugged Green with white tracer - 5v and turn the key she starts :D
Im yet to check if its a fault in the EGR or the loom going to the EGR but Im very happy that the car is now starting and running properly.
 

JoeBra

Registered User
How did you know thats what I looked like after it started?
Thanks and hopefully my experience can help someone else.
Next steps to check with the another EGR to find out if its a solenoid or wiring and fix whatever one it is to remove warning light and just tidying the car up for MOT now and get her driving again
 

JoeBra

Registered User
Resurrection just to say when I plugged in a good egr and the car started still so fault was with the egr
 
Top