Car is a 2006 VW Golf VI Hatchback with 1.4 BLN engine, ECU: 03C 906 056 AJ with 7002 S/W, VIN : WVWZZZ1KZ6B091178
First scan found:
04147-002 / P0133 NOX Sensor, Signal too low, lower limit not reached.
04149-008 / P1035 NOX Sensor, Implausible Signal, Implausible Signal. (Active Fault)
09536-008 / P2540 Low Pressure Fuel System Sensor Circuit Range/Performance, Implausible Signal.
I couldn't get any freeze frame data out of this ECU with clone VCDS and with ODIS + 5054 clone.
Car had previously been with someone else, they replaced Low Pressure Fuel sensor and Fuel Filter with new part which did not help.
Also they checked car with fuel gauge, they found it would get up to 7 bar on low pressure side while priming and around 5 bar at idle but could not determine whether faulty software in Engine Control Unit, Fuel Pump Control Unit, faulty Fuel Pump Control Unit or faulty Fuel Pump.
Performed guided test in ODIS for P2540 which was strange. First time it seemed to only try to adapt fuel pump and failed which it said was due to bad filter. I ran the job again and it then said bad pump. After running these a new job was offered to just adapt the pump which worked every time I ran it.
After clearing codes, I drove approx. 4 miles until fuel pressure fault came back, and engine light came on approx. 2 miles after this, still just fuel pressure fault. Car still driving nicely with this fault, but without fault can barely notice is engine running at idle but with P2540 engine feels rougher at idle.
I wished to observe Measuring Block 106.2 only shows pump on/off, could not find duty cycle of pump anywhere.
Also I noticed strange behavior in live data. I believe Measuring Block 103 is the most relevant one for this issue, but the meaning of 103.2 is not obvious.
103.1 - Pressure reading at Low Pressure Fuel Sensor I believe
103.3 - Learn offset after adaptation of Low Pressure Fuel Pump I believe. (Offset between Low Pressure Sensor vs which other reading though?)
103.4 - Status of pump adaptation.
ADP. OK if correctly adapted or sometimes even just after deleting fault code.
ADP. Run when adapting pump (seems to happen automatically quite often).
ERROR - when car sets P2540 fault code
Test Off, sometimes after deleting fault code says Test Off until I perform fuel pump adaptation or it will automatically start in a few minutes.
103.2 Is badly labelled in ODIS and VCDS, I suspect it is the difference between demanded and actual low fuel pressure, but I am not sure if this is demanded by Engine Control Unit or Fuel Pump Control Unit.
If I looked at live data, one time I gently increased RPM, and 103.2 was very slightly negative at approx. 4000 rpm and immediately 103.4 showed ERROR and P2540 fault was set.
To me this looked like fault was set by excess fuel pressure. However normally at idle I observed approx. 3.8 bar. However if I turned the car off and on again and left it to idle for a few mine this value could change up to 4.8 bar sometimes.
If I revved the car I observed up to 6.5 bar sometimes but only around 4.5 most of the time. However every time car was started it would always prime with over 5 bar pressure.
If I cleared P2540 when it came and left car running for a while it would eventually adapt with 977 mbar offset for Low Pressure system which seemed to be the absolute limit - it seemed like this was this highest number ECU could read.
I checked to see if I could update the fuel pump module, but this does not appear in any lists of fitted control units, and I can't find any update for the ECU in this car.
From what I have seen this must be a genuine issue with fuel pressure if ECU keeps going back to maximum adaptation very quickly. However most of the time I see positive values in 103.2 (approx 200-900) which makes me think problem is that pressure is too low. Car spends much more time with low pressure, but sometimes pressure is too high, and it seems like it is more likely to set fault code when pressure is too high.
So I have reached the same conclusion as the last people who looked at this car.
Fuel filter and pressure sensor replaced with new.
If pump is weak, why do I get high pressure sometimes?
If pump control module is faulty, how does the pump properly prime the car every time?
If Engine control unit was physically faulty, then pump wouldn't be expected to build more pressure at start or high rpm?
Anyone got any ideas for me as I can't think of any other way to prove anything without purchasing parts and keeping fingers crossed?
First scan found:
04147-002 / P0133 NOX Sensor, Signal too low, lower limit not reached.
04149-008 / P1035 NOX Sensor, Implausible Signal, Implausible Signal. (Active Fault)
09536-008 / P2540 Low Pressure Fuel System Sensor Circuit Range/Performance, Implausible Signal.
I couldn't get any freeze frame data out of this ECU with clone VCDS and with ODIS + 5054 clone.
Car had previously been with someone else, they replaced Low Pressure Fuel sensor and Fuel Filter with new part which did not help.
Also they checked car with fuel gauge, they found it would get up to 7 bar on low pressure side while priming and around 5 bar at idle but could not determine whether faulty software in Engine Control Unit, Fuel Pump Control Unit, faulty Fuel Pump Control Unit or faulty Fuel Pump.
Performed guided test in ODIS for P2540 which was strange. First time it seemed to only try to adapt fuel pump and failed which it said was due to bad filter. I ran the job again and it then said bad pump. After running these a new job was offered to just adapt the pump which worked every time I ran it.
After clearing codes, I drove approx. 4 miles until fuel pressure fault came back, and engine light came on approx. 2 miles after this, still just fuel pressure fault. Car still driving nicely with this fault, but without fault can barely notice is engine running at idle but with P2540 engine feels rougher at idle.
I wished to observe Measuring Block 106.2 only shows pump on/off, could not find duty cycle of pump anywhere.
Also I noticed strange behavior in live data. I believe Measuring Block 103 is the most relevant one for this issue, but the meaning of 103.2 is not obvious.
103.1 - Pressure reading at Low Pressure Fuel Sensor I believe
103.3 - Learn offset after adaptation of Low Pressure Fuel Pump I believe. (Offset between Low Pressure Sensor vs which other reading though?)
103.4 - Status of pump adaptation.
ADP. OK if correctly adapted or sometimes even just after deleting fault code.
ADP. Run when adapting pump (seems to happen automatically quite often).
ERROR - when car sets P2540 fault code
Test Off, sometimes after deleting fault code says Test Off until I perform fuel pump adaptation or it will automatically start in a few minutes.
103.2 Is badly labelled in ODIS and VCDS, I suspect it is the difference between demanded and actual low fuel pressure, but I am not sure if this is demanded by Engine Control Unit or Fuel Pump Control Unit.
If I looked at live data, one time I gently increased RPM, and 103.2 was very slightly negative at approx. 4000 rpm and immediately 103.4 showed ERROR and P2540 fault was set.
To me this looked like fault was set by excess fuel pressure. However normally at idle I observed approx. 3.8 bar. However if I turned the car off and on again and left it to idle for a few mine this value could change up to 4.8 bar sometimes.
If I revved the car I observed up to 6.5 bar sometimes but only around 4.5 most of the time. However every time car was started it would always prime with over 5 bar pressure.
If I cleared P2540 when it came and left car running for a while it would eventually adapt with 977 mbar offset for Low Pressure system which seemed to be the absolute limit - it seemed like this was this highest number ECU could read.
I checked to see if I could update the fuel pump module, but this does not appear in any lists of fitted control units, and I can't find any update for the ECU in this car.
From what I have seen this must be a genuine issue with fuel pressure if ECU keeps going back to maximum adaptation very quickly. However most of the time I see positive values in 103.2 (approx 200-900) which makes me think problem is that pressure is too low. Car spends much more time with low pressure, but sometimes pressure is too high, and it seems like it is more likely to set fault code when pressure is too high.
So I have reached the same conclusion as the last people who looked at this car.
Fuel filter and pressure sensor replaced with new.
If pump is weak, why do I get high pressure sometimes?
If pump control module is faulty, how does the pump properly prime the car every time?
If Engine control unit was physically faulty, then pump wouldn't be expected to build more pressure at start or high rpm?
Anyone got any ideas for me as I can't think of any other way to prove anything without purchasing parts and keeping fingers crossed?