Diagnosing fuel pressure problem in Audi Q7 - P2294 code

   #22  

dsnads

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Hi Dana,

I would like Ross Tech help with a couple things please...going back to the beginning of this thread on how to diagnose the problem.
- how to measure 1. lift pump PSI and volume. How do I do that with the VCDS? (This is what Jack said to check first.)
- what Block/Group to see what pressure in Bar the HPFP is putting out? I had read on the Wiki that it was between 25 to over 100 bar.
Thanks very much.
 
   #23  

Jack@European_Parts

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Just keep in mind that if sensors report PSI wrong in VCDS...... the only way to double check is with mechanicals and is always highly recommended.

Keep in mind you have an electrical issue not a FP issue........
 
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dsnads

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It seemed electrical on the autoscan showing 11V...but I think I had pulled over and run the autoscan With the key only in the on position and not running. Maybe the battery was just low then?

So this am with the OXS reconnected, in Group 003 showed charging over 14V. I also tried to start the car with the fuel pump relay disconnected, and it turned over but wouldn't start. That's why I am asking the Ross Tech guys for exactly which group I can diagnose the HPFP as the problem. You had Saudi. The beginning the high pressure fuel pumps fail often. If I can confirm its the likely problem, then I will inspect it mechanically. Make sense?
 
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Jack@European_Parts

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Make sense?
It makes as much sense as a 10 foot Wookie on planet Endor.

WTF are you doing pulling relays and tests from the hip.......Time to RTFB WD and pay attention to the stamps in the DTC.


-------------------------------------------------------------------------------
Address 01: Engine (BHK) Labels: 03H-906-032-BLV.lbl
Part No SW: 03H 906 032 DA HW: 03H 906 032 G
Component: Q7 3.6-FSI-LEV2 G 3234
Revision: 5CH05--- Serial number:
Coding: 0001175
Shop #: WSC 31414 790 00001
VCID: 64C76CF3A7ABD001EA7-8031

1 Fault Found:
008852 - Fuel Pressure Regulator Valve (N276)
P2294 - 004 - Open Circuit - Intermittent - MIL ON <<<<<<<<<<<<<<<<<<<<< PSSST Open Circuit !
Freeze Frame:
Fault Status: 10100100
Fault Priority: 0
Fault Frequency: 6
Reset counter: 255
Mileage: 108540 km
Time Indication: 0
Date: 2015.07.30
Time: 07:04:22

Freeze Frame:
RPM: 690 /min
Load: 29.0 %
Speed: 0.0 km/h
Temperature: 69.0°C
Temperature: 30.0°C
Absolute Pres.: 1000.0 mbar
Voltage: 14.224 V

Readiness: 0010 0101
 
   #26  

DrPeter

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Hi, I am diagnose a fuel pressure problem in 2009 3.6L Gas Audi Q7.
Like Jack said above, this is an electrical fault so we need to take that approach when attempting to fix this vehicle.


I would like Ross Tech help with a couple things please...going back to the beginning of this thread on how to diagnose the problem.
- how to measure 1. lift pump PSI and volume.
008852 - Fuel Pressure Regulator Valve (N276)
P2294 - 004 - Open Circuit - Intermittent - MIL ON
The fault code actually refers to the N290-Fuel Metering Valve , for the BHK engine. So look for this when using the factory wiring diagrams.

Below is a link to a forum post I made that can be very useful when testing these type of faults, the [Open circuit] one you have.

Testing - Open Circuits, Short to Ground or Positive, etc....




How do I do that with the VCDS? (This is what Jack said to check first.) - what Block/Group to see what pressure in Bar the HPFP is putting out?

- You can use VCDS to see the [Actual] and the [Specified] high side fuel pressure which is controlled by the N290, but these MVBs do not show you voltage at the N290..

MVB-231 field 2 = Rail Pressure,(specified)
and field 3 = Rail Pressure,(actual),Tolerance (to specified): ±5.0 bar


- You will need check the voltage to the N290 = Battery voltage (Hint: comes from fuse S13). The other side of the N290 is a pulsed ground controlled by the ECM.

- This fault code will set if the ECM does not see the minimum voltage passing through the coil of the N290 on the ground side.

P2294 - Info
• Signal voltage: 1.40 - 3.20 V = (Open Circuit)
• Signal pattern incorrect, (Rationality Check)


N290 - Fuel Metering valve
- Internal resistance @ 20'C = 1.25 to 1.55 ohms (BKH 3.2L)



Not all fault codes can or should be diagnosed with the scan tool... ;)



Hope this helps,

drpeter


ps... I thought Wookiee avg height was 2.1 meters :p
 
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dsnads

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First guys, I am nowhere near Wookie height, not as smart either. Forgive me I would rather chew my arm off than take this to the Audi dealer.

DrPeter, thanks for the detailed suggestions! I am away and won't get to try these until Friday. Looking forward to it, and will report back.
 
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Jetta 97

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I have seen this in 2.0 T cars and High pressure Pump was bad.
As DrPeter suggested , check MBV 231
 
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dsnads

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Thanks Jetta.97.
I will check 231 right when I get back today. Is there a way to inspect the HPFP, if I can remove it from the car? Problem is in the Q7 it is right against the firewall, not easy to access the bolts securing it on the engine.
 
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Jack@European_Parts

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Is there a way to be absolutely sure what is causing this problem? I have read that sometimes the HPFP needs to be completely replaced as does the cam follower.
But I am reluctant to do that without a certain diagnosis, since it will be over $1000 to do.

I have seen this in 2.0 T cars and High pressure Pump was bad.
As DrPeter suggested , check MBV 231

Correct Marin....

The regulator is part of the HP pump and normally not a spare part....... it is absolutely possible.

However, I have seen more issues with a cam ramp or follower causing a flutter resonance, this excessive vibration creates an electrical disruption to the N290/N276.

Now the OP wanted to be sure......
This is why I would test the harness and ECU via WD, and because these also fail for connectivity issues.

It only takes time to inspect a cam/lobe ramp/follower and it would be my first check along with mechanical/PSI/volume tests

PSI checks in VAS/VCDS have proven in worn ranges " unreliable" when needing to know for sure.
It only reports what it is permitted to see by the ecu's sample rate and thresholds.......many times misleading...especially under loads.

Manual measurements with a true glycerin gage and volume tests, are the only sure way to know in addition to mechanicals being inspected.
 
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dsnads

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Hi Jetta.97, here is the screenshot of MVB 231. It looks like not all the readings are showing that are supposed to.
The engine was running at this time at idle. Field 3 says Test OFF.

http://imgur.com/E61NMqP

I have also included MVB 103 and 141. See on 141 Field 1 and 2 are at 0 Bar.
Does this diagnose the problem as a broken HPFP or more electrical troubleshooting?
Thanks!!
 
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Jack@European_Parts

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The test in 103 is done in basic settings not measuring blocks.

0x01-04-103 asking ecu to do a test.
0x01-08-103 results of test and block values real time in action.

Trying to only use VCDS to determine if the HPP is bad is not the correct way to diagnose this issue.

 
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dsnads

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Thanks Jack I am guilty because don't have the WD or Fine Book.

I was replying to Jetta97 and DrPeter asking to see the MVB 231....
 
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Jack@European_Parts

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Respectfully........well if you want to be sure of things, it is time to get that fine book.

The short cut is the long way.......
 
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   #35  

Jetta 97

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Correct Marin....

The regulator is part of the HP pump and normally not a spare part....... it is absolutely possible.

However, I have seen more issues with a cam ramp or follower causing a flutter resonance, this excessive vibration creates an electrical disruption to the N290/N276.
This pump do not have follower, it is new design with roller.
 
   #36  

Jetta 97

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Hi Jetta.97, here is the screenshot of MVB 231. It looks like not all the readings are showing that are supposed to.
The engine was running at this time at idle. Field 3 says Test OFF.

http://imgur.com/E61NMqP

I have also included MVB 103 and 141. See on 141 Field 1 and 2 are at 0 Bar.
Does this diagnose the problem as a broken HPFP or more electrical troubleshooting?
Thanks!!
Your pressure is way to low, I can bet this is bad pump problem.
 
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Jack@European_Parts

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This pump do not have follower, it is new design with roller.
FYI Marin:
Any device which is driven by a cam lobe and lifted to do work is a " follower " , whether it uses a roller or a flat face lift, because it follows the cam lobe.

If you really want to get technical it is a tappet......based on repair manual or etka.
Why you felt the need to quote this and state this is beyond me, because they all mean the same thing. :banghead:

If there is a mechanical problem, it still needs to be explored.......and rollers/tappets/followers/rockers...... all break, and are the same/essential end function!

https://www.google.com/search?q=cam...ved=0CAYQ_AUoAWoVChMIwvPvqpCXxwIVTBoeCh0Q_gsj

Considering the roller is a cheap spare part, it would be wise too inspect/measure, verse just buy or condemn an HPP.

Just because a new design was implemented which is better for friction, doesn't mean that there still isn't a lubrication issue inherent in theses engines.

Cars with rollers still throw chains and adjusters still break........
Most of the time it is due to exceeded friction by such pumps/followers binding, all due to inadequate oiling volume....... that cause internals like this to fail!
 
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   #38  

dsnads

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Thanks Jetta97 and Jack.
Based on this I am going to inspect the cam follower/roller/tappet.
If someone knows where I can buy the fine book for a Q7 please let me know.
Also do I need to take the whole HPFP off to inspect this part?
 
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Jack@European_Parts

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www.erwin.audi.com

It is always recommended to remove pump and inspect the lifter in addition to the lift stroke of the cam lobe or lobes for full maximum travel.

For serious lubrication issues causing excessive wear to the cams or pressed on cam lobe ramp sometimes a cam is needed.

If this is the case you'd better inspect the oil sump and output of PSI and adequate volume.

Respectfully based on your aforementioned approach/responses to this repair ........it maybe over your skill level.
 
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dsnads

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Hi Jack thanks again. It may be over my skill level, but will take it slow and report back...
 
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