Advertise on DISCO3.CO.UK
Forum · Gallery · Wiki · Shop · Sponsors
DISCO3.CO.UK > Technical (D3)

Help needed with Fault Code P0194
Post Reply  Down to end
Page 1 of 2 12>
wedgev8
 


Member Since: 17 May 2019
Location: Kerpen
Posts: 181

Germany 2008 Discovery 3 TDV6 HSE Auto Java BlackDiscovery 3
Help needed with Fault Code P0194

Help needed with Fault Code P0194 "Fuel rail pressure sensor A circuit intermittent/erratic"
The car goes into Limb mode and lowers the suspension. some other Fault codes came up, but these are only result of the P0194. I have understood it is a problem with the 5V reference voltage and I have to inspect the circuit or check the pressure sensor. (found this in the repair manual)
Did someone had also this code and can help me to solve the problem?
  
Post #209206313th Oct 2019 6:48 pm
View user's profile Send private message View poster's gallery Reply with quote
Globetrotter448
 


Member Since: 21 Mar 2017
Location: Londonderry NSW
Posts: 1771

Australia 2007 Discovery 3 4.0 V6 Petrol SE Auto Java BlackDiscovery 3

Need to make sure battery is good and has good voltage also need to make sure alternator is working correctly. If you have recently washed the engine bay, check the connectors behind the battery box.
  
Post #209211214th Oct 2019 2:02 am
View user's profile Send private message View poster's gallery Reply with quote
wedgev8
 


Member Since: 17 May 2019
Location: Kerpen
Posts: 181

Germany 2008 Discovery 3 TDV6 HSE Auto Java BlackDiscovery 3

Thanks for your reply. Battery is strong and generator makes 14V.
  
Post #209353518th Oct 2019 9:28 pm
View user's profile Send private message View poster's gallery Reply with quote
PROFSR G
 


Member Since: 06 Mar 2017
Location: Lost
Posts: 4580

Ukraine 2009 Discovery 3 TDV6 Commercial XS Auto Stornoway GreyDiscovery 3

What diagnostic tool are you using? And what are the other codes?
 yµ (idµ - eAµ) ψ=mψ

 
 
Post #209355319th Oct 2019 12:38 am
View user's profile Send private message View poster's gallery Reply with quote
wedgev8
 


Member Since: 17 May 2019
Location: Kerpen
Posts: 181

Germany 2008 Discovery 3 TDV6 HSE Auto Java BlackDiscovery 3

I have the iCarsoft LR V2.0 and also the older LR II Version.
What I have found when looking live data of the 5V sensor voltage, there are short voltage dips down to 2V one or two seconds before the fault codes and limb mode comes up.
  
Post #209356419th Oct 2019 6:50 am
View user's profile Send private message View poster's gallery Reply with quote
Globetrotter448
 


Member Since: 21 Mar 2017
Location: Londonderry NSW
Posts: 1771

Australia 2007 Discovery 3 4.0 V6 Petrol SE Auto Java BlackDiscovery 3

Would be handy to know what the 12 volts at battery was doing at the time of the dip to 2 volts
  
Post #209357819th Oct 2019 8:08 am
View user's profile Send private message View poster's gallery Reply with quote
PROFSR G
 


Member Since: 06 Mar 2017
Location: Lost
Posts: 4580

Ukraine 2009 Discovery 3 TDV6 Commercial XS Auto Stornoway GreyDiscovery 3

wedgev8 wrote:
I have the iCarsoft LR V2.0 and also the older LR II Version.
What I have found when looking live data of the 5V sensor voltage, there are short voltage dips down to 2V one or two seconds before the fault codes and limb mode comes up.


And the other codes you dismissed earlier, what are they?
 yµ (idµ - eAµ) ψ=mψ

 
 
Post #209362119th Oct 2019 1:08 pm
View user's profile Send private message View poster's gallery Reply with quote
wedgev8
 


Member Since: 17 May 2019
Location: Kerpen
Posts: 181

Germany 2008 Discovery 3 TDV6 HSE Auto Java BlackDiscovery 3

The instruments gave me a christmas tree, HDC, lowered, engine fault. The three Amigos.
With the fault reader I can find several network faults, gearbox U2023, all terrain U0401, ride Level U0416, vehicle dynatmics....

To globetrotter:. I need to have a power inverter for my scope to use it in the car while driving. Will order one the next days.
  
Post #209378119th Oct 2019 10:26 pm
View user's profile Send private message View poster's gallery Reply with quote
PROFSR G
 


Member Since: 06 Mar 2017
Location: Lost
Posts: 4580

Ukraine 2009 Discovery 3 TDV6 Commercial XS Auto Stornoway GreyDiscovery 3

I think there are one or two possibilities (amongst others) which might be causing the erratic signal at the FRPS.
Firstly the earth straps, these need to be thoroughly checked and you need to be absolutely satisfied the battery is in 100% good health. Secondly, the signals to both the PCV and VCV on the high pressure fuel pump, these need to be within their respective limits. If they are showing higher readings its a strong indicator the alternator is the culprit. Beyond that you may need to examine the wiring harness for damage. You will have to "test your way through it" in the absence of further DTC's Thumbs Up
 yµ (idµ - eAµ) ψ=mψ

 
 
Post #209378619th Oct 2019 11:41 pm
View user's profile Send private message View poster's gallery Reply with quote
Globetrotter448
 


Member Since: 21 Mar 2017
Location: Londonderry NSW
Posts: 1771

Australia 2007 Discovery 3 4.0 V6 Petrol SE Auto Java BlackDiscovery 3

If the fault appears only when driving - check the long lead from the alternator to the battery as it known to rub on the diff and occasionally shorting the power.
  
Post #209379120th Oct 2019 3:56 am
View user's profile Send private message View poster's gallery Reply with quote
wedgev8
 


Member Since: 17 May 2019
Location: Kerpen
Posts: 181

Germany 2008 Discovery 3 TDV6 HSE Auto Java BlackDiscovery 3

Thank you, I will investigate in the harness and let you know.
I have a LHD car. The wire from the alternator ist shorter and not near the diff. Wink
  
Post #209442522nd Oct 2019 7:56 pm
View user's profile Send private message View poster's gallery Reply with quote
wedgev8
 


Member Since: 17 May 2019
Location: Kerpen
Posts: 181

Germany 2008 Discovery 3 TDV6 HSE Auto Java BlackDiscovery 3

Till today I am not through with all sensor wirings which are connected to the 5V circuit.
But I have found out the following:
After starting from cold I can drive about 2 miles without the fault. Than I can feel a short judder from the engine and can see the short voltage dips. The warmer the engine, the more dips and judder from the engine till the BING comes up with the Xmas tree in dashboard and P0194.
Today I have checked the wiring to the fuel rail pressure sensor and it is in good condition. So I connected a 5V reference simulator to this circuit to have a good 5V feed for the sensor. Now I can drive more miles without the BING. The P0194 (intermittent fuel rail pressure sensor circuit) did not come up. Even though I can further See the dips on the diagnostic Screen. So I was able to found out the jerking engine came from the acceleration Pedal. When I accelerate with the cruise control without touching the pedal I have no jerking engine. But also with not touching the APP I can see the 5V dips more often and lower to 1v. And so I found out on my long test drive, when I drive smoothly with 40 to 50 Mph with no dips and give a little load on the engine (very light accelerating with the cruise control) than the dips came up. At exactlyt this point.
Hhhmm,..
  
Post #209559927th Oct 2019 9:24 pm
View user's profile Send private message View poster's gallery Reply with quote
PROFSR G
 


Member Since: 06 Mar 2017
Location: Lost
Posts: 4580

Ukraine 2009 Discovery 3 TDV6 Commercial XS Auto Stornoway GreyDiscovery 3

PROFSR G wrote:

Firstly the earth straps, these need to be thoroughly checked and you need to be absolutely satisfied the battery is in 100% good health. Secondly, the signals to both the PCV and VCV on the high pressure fuel pump, these need to be within their respective limits. If they are showing higher readings its a strong indicator the alternator is the culprit.


Did you check as described above?
If so what values were present at the PCV and VCV? From experience it seems to me like an alternator issue! As a "wild card" you could try changing the brake light switch as this is a well known devil for wacky erratic electronic behaviour. (cheap) The iCarsoft reader is generally a good scan tool and works well on LR, but I'm wondering if a more dedicated tool would reveal more!!
 yµ (idµ - eAµ) ψ=mψ

 
 
Post #209562828th Oct 2019 1:45 am
View user's profile Send private message View poster's gallery Reply with quote
wedgev8
 


Member Since: 17 May 2019
Location: Kerpen
Posts: 181

Germany 2008 Discovery 3 TDV6 HSE Auto Java BlackDiscovery 3

To my shame I had not checked the earth points yet. For this I have to put the car on jacks to remove the wheels and to get underneath. I am planning to do this next week when I am not at work.
The battery is checked by a friend last week. He has a battery health tester to test batteries voltage under load. For the PCV and the VCV I have no values to decide if these are good. But when these values are not in range, I think new DTCs should come up for this. Further I have the problem with my scope. I can not use it in my car while driving to read the values for PCV and VCV.
The brake light switch I have changed to a new one some days ago. Didnt´t help.
What do you think about driving with disconnected alternator? Only a few miles driving on battery should show if there are already the voltage dips. Or could it be possible to destroy the alternator with no connected battery? For this point I could connect a second battery wich only is connected to the alternator to give him a load. What I also can do is disconnecting the battery after starting the engine and drive only on alternator. So it should 100% sure the battery is not faulty.
By the way, I think buying a better diagnostic tool should help checking live values while driving.
Is the Gap IID tool a good idea to see some values shown as scope curves on the display?
  
Post #209578028th Oct 2019 6:29 pm
View user's profile Send private message View poster's gallery Reply with quote
PROFSR G
 


Member Since: 06 Mar 2017
Location: Lost
Posts: 4580

Ukraine 2009 Discovery 3 TDV6 Commercial XS Auto Stornoway GreyDiscovery 3

GAP IID is the tool of choice for most members on here as it is invaluable for D3/4 ownership. The iCarsoft you have is a good starter tool but it is very limited. The GAP tool can do much more as well as a thorough read of the modules. It will quickly pay for itself and has a very good re-sale value should you decide to move on. The reference value for the VCV and PCV is around 4.9V, make sure the earth straps under the bonnet as well as the NSF wheel arch and transfer case are checked too!
 yµ (idµ - eAµ) ψ=mψ

 
 
Post #209581528th Oct 2019 8:39 pm
View user's profile Send private message View poster's gallery Reply with quote
Display posts from the last:  
Post Reply Back to top
Page 1 of 2 12>
Jump to:  
Previous Topic | Next Topic >


Posting Rules
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum



DISCO3.CO.UK Copyright © 2004-2024 Futuranet Ltd & Martin Lewis
DISCO3.CO.UK RSS Feed - All Forums

DISCO3.CO.UK is independent and not affiliated to Land Rover.
Switch to Mobile Site