[ATCer]

Hi

So here's the story so far. 3 weeks ago my car kept going into limp mode and the CEL light came on. It seemed to put itself into limp mode before the engine was even started, but I could reset it by turning ignition on/off and then would behave normally and no more limp mode behaviour seen during that drive. VCDS came up with the following fault code information:

18000 - Altitude Sensor/Boost Pressure Sensor
P1592 - 000 - Implausible Correlation
Freeze Frame:
RPM: 0/min
Torque: 2.0Nm
Speed: 0.0km/h
Load: 0.0%
Voltage 12.24 V
Bin. Bits: 00001100
Absolute Pres: 1009.8 mbar
Absolute Pres: 1122.0 mbar

My understanding of this was that the MAP sensor and the atmospheric pressure sensor were not showing the same value when the engine was off (which of course they should be as the engine is not running - therefore boost pressure should be the same as atmospheric pressure). So the car realises the sensor is misreading and puts the car into limp mode to try and prevent engine damage. So it made sense to me that the MAP sensor must be faulty. I replaced the MAP sensor and everything was back to normal. Then this morning (2 weeks later) I'm now getting occasional limp mode again with exactly the same fault on VCDS. So I guess my MAP sensor was probably fine all along. So what is the problem with my car!?!? Has anyone else had this issue??

BTW, car is a 2004 GT 2.0TDI BKD Golf.

Cheers

Ben

 

[jaycoupe]

I had a boost pressure sensor error that came up on diagnostics on my MK5. Common problem it seems, it needed some rewiring done. Not sure where abouts it was located but I'm pretty confident yours is a wiring fault too, but get it checked at VW. Cost me around ?100.

 

[ATCer]

Hi

Thanks for your reply - I think I've solved the problem now and you were dead right, it was a wiring loom fault. Now I've finally got to the bottom of this I will post up my results for future reference should anyone else get the same issue.

It became apparent there must be a wiring fault somewhere (too much resistance in the circuit confusing the ECU into thinking there is a boost sensor fault). I figured there must be a dirty connection somewhere as the car has been fine for 8 years. Made sense to me it was probably a dirty earth point at fault as these are the most exposed parts of the loom. All the earth points are located under the air filter housing near the battery on the BKD engine.

I removed the air filter box which revealed all the
ground points for the engine bay wiring loom. I figured there must be a
problem where the loom itself is grounded because the MAP sensor is
screwed to a plastic (insulated) pipe and touches no metal! I plugged in
VCDS and then twisted and tugged on the ground points while a friend of mine
watched the computer. Hey presto!!! One of the earths altered the MAP sensor reading on VCDS when I moved it. So I cleaned up all the
earth connections (they all had traces of paint on from when the car was sprayed which were
clearly preventing a flush connection to the wiring), put it all back
together and now no obvious problems! I've re-read the MAP sensor reading
several times, and it now matches the atmospheric pressure reading as it should do. And the
bonus part is the car is much more responsive! There is definitely much less turbo lag and it picks up much quicker at speed. I guess the MAP sensor was always
overreading before so the ECU was never demanding enough boost, making
for a very laggy drive.

So there you go! I'll double check it again in a couple of weeks and make sure both values still read the same, but I'm pretty confident problem solved. I was getting quite worried because everywhere else I've read online says a P1592 code on a BKD engine always means new turbo. To me this never made sense as the code was only ever triggered with the engine not running, and it is not an overboost condition.

Hope it's helpful to someone else.

Ben

 

[Brolle]

Hi

Thanks for your reply - I think I've solved the problem now and you were dead right, it was a wiring loom fault. Now I've finally got to the bottom of this I will post up my results for future reference should anyone else get the same issue.

It became apparent there must be a wiring fault somewhere (too much resistance in the circuit confusing the ECU into thinking there is a boost sensor fault). I figured there must be a dirty connection somewhere as the car has been fine for 8 years. Made sense to me it was probably a dirty earth point at fault as these are the most exposed parts of the loom. All the earth points are located under the air filter housing near the battery on the BKD engine.

I removed the air filter box which revealed all the
ground points for the engine bay wiring loom. I figured there must be a
problem where the loom itself is grounded because the MAP sensor is
screwed to a plastic (insulated) pipe and touches no metal! I plugged in
VCDS and then twisted and tugged on the ground points while a friend of mine
watched the computer. Hey presto!!! One of the earths altered the MAP sensor reading on VCDS when I moved it. So I cleaned up all the
earth connections (they all had traces of paint on from when the car was sprayed which were
clearly preventing a flush connection to the wiring), put it all back
together and now no obvious problems! I've re-read the MAP sensor reading
several times, and it now matches the atmospheric pressure reading as it should do. And the
bonus part is the car is much more responsive! There is definitely much less turbo lag and it picks up much quicker at speed. I guess the MAP sensor was always
overreading before so the ECU was never demanding enough boost, making
for a very laggy drive.

So there you go! I'll double check it again in a couple of weeks and make sure both values still read the same, but I'm pretty confident problem solved. I was getting quite worried because everywhere else I've read online says a P1592 code on a BKD engine always means new turbo. To me this never made sense as the code was only ever triggered with the engine not running, and it is not an overboost condition.

Hope it's helpful to someone else.

Thanks ATCer! After googling around many hours I finally found someone talking sense I had exactly the same issue with my Touran (golf mk5) with 170ps TDI/DSG.

When igntion [ON] sometimes the engine error telltale lit and when reading out the fault code with my cheap ebay OBD-tool, faultcode was MAP sensor out of range. *I have to buy vag-com*

This could not be turbofailure since the engine isn't even running.

I did the same - checked the two ground connections under the airfilter, sprayed contact oil into the connectors and presto! No engine fault!

This "VW solution" of grounding isn't to impressing by the way, just a matter of time until the connection fails.

Big thanks for the post! Costed me null to fix. Sometimes magic happens

//Brolle, Sweden

 

[jon-1987]

Hi All,

I have been having problems with my Golf MK5 GT 170 TDI.
As soon as l turn the ignition on, occasionally l get the flashing heater plug flashing light and car is in limp mode on start-up
I have replaces the Turbo Boost Sensor and still the same.
The problem is intermittent and happens about 3 times a week
Car drives perfectly once l restart the engine.
Have have used VAG COM and get the following errors:
Any suggestions?
Thanks,
JON

2 Faults Found:

<a>005522</a> - Altitude Sensor / Boost Pressure Sensor

P1592 - 006 - Implausible Correlation - Intermittent

Freeze Frame:

Fault Status: <a>00100001</a>

Fault Priority: 5

Fault Frequency: 242

Reset counter: 40

Mileage: <a>174749</a> km

Time Indication: 0

Date: 2000.00.00

Time: 07:38:23

Freeze Frame:

RPM: 0 /min

Torque: 0.0 Nm

Speed: 0.0 km/h

0.00 %

Voltage: 11.19 V

Pressure: 958.5 mbar

Pressure: 1128.9 mbar

<a>000257</a> - Mass Air Flow Sensor (G70)

P0101 - 006 - Implausible Signal - Intermittent

Freeze Frame:

Fault Status: <a>00000001</a>

Fault Priority: 1

Fault Frequency: 9

Reset counter: 36

Mileage: <a>184149</a> km

Time Indication: 0

Date: 2000.00.00

Time: 08:13:52

Freeze Frame:

RPM: 1248 /min

Torque: 0.0 Nm

Speed: 40.0 km/h

Temperature: 0.0∞C

Pressure: 1256.7 mbar

Text: 68 kg/h

(no units): 1.22

 

[Compaq]

Hi can someone please tell me which ground wire controls boost preasure sensor i am having the same problem a picture would be great. Please help its doing my head in intermittent fault

 

[jon-1987]

I cleaned all the earth wired below the battery holder, that got rid of the problem for about 3 months and then started intermittently again. Still not had time to have a further look. Have you managed to sort yours out?

 

[FLAPPERJACK76]

Had same faults. In the end had to rewire from boost sensor to ecu. Completely removed wiring by de pinning from ecu harness. There was a connection to under the air filter housing on mine. I rewired from boost sensor to multi plug first but fault came back. So wired straight to ecu. Been 2 year's now and it's still good.

Sent from my SM-G900F using Tapatalk

 

[jon-1987]

Would you be able to provide some photos of the wires that go into the ECU.

Going to sort mine out next week. Any additional info would be great.

Thanks,

Jon

 

[wasimthedan]

Had same faults. In the end had to rewire from boost sensor to ecu. Completely removed wiring by de pinning from ecu harness. There was a connection to under the air filter housing on mine. I rewired from boost sensor to multi plug first but fault came back. So wired straight to ecu. Been 2 year's now and it's still good. Sent from my SM-G900F using Tapatalk

How much was the wiring? hard job?