Hello!

Jaguar S-type, 2004 YOM. 4.2L
I have troubles speeding up, engine chokes. Trouble code p1235 showing up on diagnostics (Fuel Pump Control out Of Range (Fuel Pump Driver Module/VLCM)).

I have checked the following things:
-fuel pressure at rail is 30psi, no fuel leak anywhere.
-control signal coming to fuel pump is about 6-7V (Simple Voltmeter in DC mode, will take a look at oscillosope tomorrow), so yet Duty cycle of PWM seems to be about 50%
-pump can give up to 87psi pressure on the testbench. Pump is fine.
-filter is not clogged. fuel is good.

Looking for some advise, what to check else.
Tomorow I will continue diagnostics.

Best regards,
Alexander

 

Hi Alex,

Fuel pressure is low. Signal to the fuel pump should be at least 10.5V or higher (I believe)

Had the fuel filter been changed? You say it's good but when was it changed last and if recently, was it installed in the right direction?

That's my $0.02 for now.

 

Hello,

Thank you for response! I have checked filter earlier and it seemed to be clean, but now I have changed it and the problem is solved!

Thank you very much!

 

How exactly does one go about checking a fuel filter that is encased entirely by steel?

 

Unless it's cut open I think it's an inexact process!

 

Yes, I see. Even once I took it out, I cut it and it seemed to be cool. It was just unexpected for me that it was real reason.

 

wrong thread