P1198 Limp Nightmare solved?

[noobz]

I'm gonna write a long post because my car is posesed by a limp mode demon. p1198(fuel pressure regulator) rarely acompanied by P1165(fuel rail pressure sensor)

I have a C4 coupe 2.0 HDI with Siemens pump.EGR and FAP OFF and remaped too 160HP+. For 6 months i have been strugling with limp mode when hard accelerating especialy in the higher gears. Went to a diesel specialist checked the injectors corection was almost perfect, checked the return of the injectors all were fine. I did 2 logs on heavy acceleration with the diesel specialist in the car and he confirmed the HP pump delivered enough pressure. They checked all plugs and wires all fine. The guy sugested i should change the Fuel Pressure Regulator. I changed it with and original VDO and no diference.

I have been too 3 more mechanics.. they sugested changing the HP pump. I told them... if u put a new HP pump and it's gonna go intoo limp mode again u will put my old HP pump back. None of them accepted and i'm not a gambler.

I tried my luck with a Liqui Moly diesel purge, bypased the fuel tank and the fuel filter and i Burned! my hand on that can it got so hot! Reconected the fuel lines.. same P1198 Limp-mode on hard acceleration !

After a week i started to think.. obout that extremly hot diesel from the liqui moly diesel purge cann... and i disconected the Fuel Pre-heater under the Intake " Y " and gues what... Never saw a P1198 error again.Hard acceleration Upphill.. done more than 500km reached 170Km/h on highway.. no limp...
I searched the internet for something similar to what i have experienced and nothing, How does this fuel pre-heater work? Is it ON all the time or is it controled by the ECU ? Do i have a Fuel Temperature sensor? In Romania the temperature is 30 Celsius so its not like im runing cold diesel witch would help my old HP pump get higher pressure.

[Bick]

Wow thats a really weird one - thank you so much for sharing this, top man.

I presume the fuel heater is controlled by the ecu just like everything else on these modern diesels

[Joelious219]

I have this exact issue where is the fuel heater located?

[Joelious219]

I have 407 SW

[robertel99]

I'm gonna write a long post because my car is posesed by a limp mode demon. p1198(fuel pressure regulator) rarely acompanied by P1165(fuel rail pressure sensor)

I have a C4 coupe 2.0 HDI with Siemens pump.EGR and FAP OFF and remaped too 160HP+. For 6 months i have been strugling with limp mode when hard accelerating especialy in the higher gears. Went to a diesel specialist checked the injectors corection was almost perfect, checked the return of the injectors all were fine. I did 2 logs on heavy acceleration with the diesel specialist in the car and he confirmed the HP pump delivered enough pressure. They checked all plugs and wires all fine. The guy sugested i should change the Fuel Pressure Regulator. I changed it with and original VDO and no diference.

I have been too 3 more mechanics.. they sugested changing the HP pump. I told them... if u put a new HP pump and it's gonna go intoo limp mode again u will put my old HP pump back. None of them accepted and i'm not a gambler.

I tried my luck with a Liqui Moly diesel purge, bypased the fuel tank and the fuel filter and i Burned! my hand on that can it got so hot! Reconected the fuel lines.. same P1198 Limp-mode on hard acceleration !

After a week i started to think.. obout that extremly hot diesel from the liqui moly diesel purge cann... and i disconected the Fuel Pre-heater under the Intake " Y " and gues what... Never saw a P1198 error again.Hard acceleration Upphill.. done more than 500km reached 170Km/h on highway.. no limp...
I searched the internet for something similar to what i have experienced and nothing, How does this fuel pre-heater work? Is it ON all the time or is it controled by the ECU ? Do i have a Fuel Temperature sensor? In Romania the temperature is 30 Celsius so its not like im runing cold diesel witch would help my old HP pump get higher pressure.

hey, I'm from Romania as well, and I am fighting the same demon but on a 407. Where exactly is this fuel pre-heater? Do you have a photo by any chance?

[Tsvet Todorov]

Hello, I have the same error p1198 and the car goes into limp mode. I saw you fixed the issue with: and i disconected the Fuel Pre-heater under the Intake " Y " and gues what...

can you please give me some more info on that part and what actions did you do. Did you got the error again after this?
thanks in advance.

[robertel99]

Hello, I have the same error p1198 and the car goes into limp mode. I saw you fixed the issue with: and i disconected the Fuel Pre-heater under the Intake " Y " and gues what...

can you please give me some more info on that part and what actions did you do. Did you got the error again after this?
thanks in advance.

hey, I commented on this earlier than you. I have the same issue, I heard the fuel preheater is on the cover of the fuel filter, so the plug on the cap of the cover is from the fuel heater. the plug that he refers to, and that I was looking for, is under the air doser, in the circled area. it is the plug for the diesel temperature sensor, and I can confirm that after unplugging that, there will be no more p1198, however there will be a tiny reduction in performance, nothing crazy though.

[boko88]

Does anyone found what is real issue for p1198 ?

[robertel99]

Does anyone found what is real issue for p1198 ?

I'm not sure. But with that sensor unplugged its working great. Had it unplugged for a few months now and no more errors.