P1235 Jaguar Fuel Pump Control Out Of Range

Engine light came on with no other discernable symptoms. From the list below, how do I diagnose & fix?

Possible causes
– Faulty Fuel Pump Drive Module (FPDM)
– FPDM harness is open or shorted
– FPDM circuit poor electrical connection
– Faulty Powertrain Control Module (PCM)
Symptoms
– Engine Light ON (or Service Engine Soon Warning Light)
P1235 Jaguar DescriptionThe P1235 Jaguar code indicates the Fuel Pump Drive Module (FPDM) detected an invalid or missing Fuel Pump (FP) circuit signal from the Powertrain Control Module (PCM). The FPDM sends a message to the PCM through the FPM circuit, indicating this failure was detected. The PCM sets the DTC when the message is received.

Thanks & Best,

Steve

 

I have an intermittent P1235 - did not set engine light. Symptoms... excessive cranking when ambient temp.is cold, although it's been happening more often.

I changed out the fuel pump driver behind the REM with a known good one, no change.

The REM controls the main fuel pump and the fuel pump driver controls the secondary fuel pump (passenger side)

Now, I watched fuel pressure while driving and floored it to kick on the secondary pump and my fuel pressure rose to 65 - 70 psi.

My thinking... the secondary fuel pump is on the way out. Also I believe the 2 way check valve has failed by not maintaining fuel pressure at the rail. There are 2 of these 2 way valves. Both are on the main line that feeds the fuel rail.

I'm swapping out the secondary fuel pump assembly when it arrives. Hopefully this will resolve my issues. I also have a primary fuel pump assembly on the way as well.

I have 2 good Pierburg fuel pumps removed from good assemblies as back ups..

Again, my P1235 is intermittent and only caught it with a full scan via IDS.

 

Sounds like you have quite a lot going on. Good luck. Is there no one with an answer to my query? Where are all of the guys I used to know on this forum? Seems like a different place!

 

Apologies my response was not good enough for your query. Your right... the forum is NOT the same place anymore....

 

Ababono, no need to apologize. I hope you get your issue solved: wish I knew enough to help.

If the code fault I'm getting is accurate, I would think that I would have noticeable symptoms in addition to the check engine light.

 

Sorry but your query is not leading to the solution, it looks like the information comes from a non-genuine diagnostic system.

On an 04 XJR, DTC P1235 means that the pulsewidth modulated input signal given from the ECM to the REM is lower than than expected. Specifically, this affects the cable connection PI1-27 (output ECM) to CR11-19 (input REM) with a total of 4 connectors beetween.
To solve the problem, the cable connections have to be checked, i.e. the resistances and ground connections must be measured. The pinpoint tests for this can be found in the SDD diagnose system.

Good luck.

 

Thanks, Flatsix, for the substantive response. I copied & pasted from the Worksop Manual. Will study what you have said & double check the info I sent. It just dawned on me that I may have cut & pasted from another site. Will try to figure it out. Thanks again. Steve

 

Found the reference to "Carryout any pinpoint tests associated with this DTC... Refer to electric circuit diagrams, ... & check engine control module to..."

Where do you find all of this? What am I looking to do? Find? Thanks. SS

 

This is what the WSM says:

P1235 Fuel Pump Control Out Of Range

Rear electronic module, fuel input (modulated pulsewidth) - out of range (low)

​​​​​​Carry out any pinpoint tests associated with this DTC using the manufacturer approved diagnostic system. Refer to electrical circuit diagrams, notes and check engine control module to rear electronic module fuel input (modulated pulsewidth) is out of range (low)

The Pin information comes from the wiring diagram 2005 Jaguar XJ, Engine Management V8 SC.

Accordingly, the 150 Hz signal from the ECM is outside the expected range (4% - 51%). It may be that the signal given out from the ECM is already too weak, but more likely there are voltage losses or ground faults on the way from the ECM to the REM.

This can be measured with a multimeter, or even better with an ( handheld) oscilloscope. However, I recommend diagnosis and measurement with the original IDS/SDD, because all information about the target values and the affected pins are available there.

If you are lucky, it will solve the problem if you pull the affected connectors several times apart and push it together again.

Fritz

​​​​​​

 

Thanks so much, Fritz!

"If you are lucky, it will solve the problem if you pull the connectors several times apart and push it together again."

If I can find the ECM & REM (I assume they are next to each other?) I will play with unplugging & plugging in the connectors.

If I am lucky & this does the trick, will the engine light go out by itself or do I need to reset?

I use the iCarsoft LR V.3.0. It is what gave my only P Code: P1235. Can you recommend a multimeter? I don't think I've used one before.

If this doesn't work I will look up the items you mentioned & run further tests. What are the likely fixes if the plugging & unplugging doesn't work?

 

i have the same code and I'm thinking the ecm connector might be corroded. haven't had a chance to check it yet but i did have clogged drains causing water on pass side front floor as far as i have researched this cod it has nothing to do with fuel pump itself and more to do with the signal from the ecm to the rem. my code is stored in the rem not in the ecm

 

I suspect the drains as well. There is much written about how to clear them and the numerous problems they can lead to on this forum.
-j

 

Hi Steve,
download the wiring diagram for your car from Jagrepair.com and take it to someone who is able tor read them and who is familiar with automotive electronics . The wiring diagram contains all the information needed, including the location of the control units in the vehicle.

​​​​​​​Good luck Fritz

 

The engine light came on while we were on 100 mile drive last week & the car is usually used as a town car with trips seldom as much as 10 miles a couple of times per week.

She hadn't been started for 6 days when I attached the diagnostic tool to her & read the battery voltage. After doing that, I started her &VOILA ! NO ENGINE LIGHT.

Since she runs like-new, I'm inclined to let her be for now & pick it up again if she lights up. Thanks for your help.