Cutting off at 4500 rpm code p1234
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tmcphail
GT Owner/Vendor
P1234 FUEL PUMP DRIVER MODULE DISABLED OR OFF LINE (Fuel Pump Driver Module) G G G
Check FPDM fuses to start.
Check FPDM fuses to start.
STORMCAT
GT
http://www.fordgtforum.com/forums/showthread.php?19332-Trouble-Code-P1235&highlight=CODE
Manny,
I bet I can correct your problem in 5 minutes. I had a similar problem. After a lengthy drive with a Ford GT tech in the car with his PC hooked up they could not find the exact problem. After some home work and some self diagnosis and parts swapping it was just the secondary fuel pump relay that went. They cost $12. and it's about a 5 minute install.. don't waste your time with the FP drivers. Go right to the relays. They are more prone to fail. The contacts are very small and will pit easy
I installed two new relays and my car ran stronger than it has for a long time. I concluded that if you run your car hard the secondary fuel pump relay pulls in and out a lot more then the primary relay so it is going to pit and fail way before the primary relay.
Me being the curious cat I am. I ripped it apart and was shocked to see how small the contact points of the relay. This is the relay that was causing my problem. The pump would run and cut out causing fuel pressure and flow issues. You can see the dark pitted contacts. You can also see this batch was made in China. The new replacements were made in the USA . I think it would be wise to replace the relays at 5000 to 7000 miles to keep them fresh. Call me tonight if you want some more info. I am leaving town tomorrow..
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FordGTGuy
Well-known member
Its quite funny to see a supercar with a 5 minute $12 repair, just goes to show how overpriced European counter parts can be.
BlackICE
GT Owner
If a dealer did the repair it would be much more than $12 and 5 minutes, but much less than a Fcar.
STORMCAT
GT
Kendal is exactly right. My problem took some time to resolve. There is a funny story evolved. Those of you who know me know I am not a professional mechanic but I am a hands on kinda guy like most of you and I'm pretty good with the wrenches. I avoid going to the dealer for any type of work. I really enjoy taking care of my own girls. When I started to experience the problem it was never at a consistent RPM some times at 4500 RPM, sometimes at 5000 RPM, sometimes at 5500 RPM etc.. a real head scratcher.
I made an appointment to go to see GT tech Mike at Saw Grass Ford. I know Mike personally and know he has worked on many a GT's. I thought he may have seen this trouble code or be familiar with the problem. I wanted him to put their diagnostic PC on my car to see what's going on. The only way to experience the problem is to go out and run the car. The problem is at over 4500 RPM in 1st or 2nd gear the car is going pretty fast so you need to be on a highway type of road.
We jumped on a highway close to the dealership to take some reading as I do some hard pulls thru the gears. It's mid day and you know what kind of attention the GT draws on the road. Cars would speed up to get next to me to catch a glimpse of the GT about that time I go roaring off high in the power band so we could take some readings. I would rapidly speed away from the onlookers.. Than I would slow down so we could look at the data. The cars would speed up to catch me and I would take off again.. after about the third time some of the same cars would pull up next to me with some strange looks on their faces. I am sure some of these people were thinking I was a real jerk wad speeding up and slowing down like I was showing off or something .. If only they knew it was All in the name of science : )
We went back to the dealership to decipher what the GT tech saw. He could read fuel pump pressure and % of duty cycle etc.. . Both were dropping off erratically and sporadically. There was no consistency only that it would happen above 4000 RPM. I didn't know much about the fuel system so the tech gave me a quick education so we could brainstorm on what might be going on. There are two fuel pumps. A primary pump and a secondary pump. The primary FP. handles the load up to 4000 RPM when the pressure drops off the second pump will kick in. Based on the fact that the car would run fine up to 4000 RPM it was obvious something was going on with the secondary pump.
The computer trouble shooting guide said to check the following items in no specific order. Fuel pump drive modules, Fuel pump leads, Fuel pump grounds, ECU grounds and leads and if need be check and or replace the fuel pumps. Mike also mention it could be anything that had to do with signaling the fuel pumps. Even possibly the Throttle position sensor. ( at this point there was no mention of the fuel pump relays by the PC trouble shooting guide or the GT tech) Mike is a straight shooting kind of guy and not really knowing where to start it sounded like a time consuming trial and error project.
I asked him about some of the specific items. He told me the Fuel pump driver modules are behind the splash shields on the passenger side fire wall and there was a dedicated fuel pump ground up near the head lights. He said it was on the passenger side but he doesn't ever recall seeing it. At this point me or any other owner would have to decide wether to leave the car in their hands to try to pin point the problem or try to do some trouble shooting on their own. I was not that keen on someone else ripping into my car so back to my shop I went.
I am lucky to have a back up GT that I could steal parts off and try them to see if something was bad.. During the course of working on and off for about a week I swapped out the Throttle position sensor, the secondary fuel pump module, and checked some of the grounds. Nothing cured the problem.. At this point I still did not know there were fuel pump relays. The way the GT tech talked I was under the impression that the Fuel pump drivers handled all of the fuel pump cycling operations.
I was a little frustrated at this point. I started to look for this dedicated fuel pump ground that the GT tech told me is up near the headlights. For the life of me I could not find it. I went to the GT wiring diagrams.. I as am looking at diagrams I see the Auxiliary relay box with ( 2 ) fuel pump relays listed. This was the point that I learned they existed. I knew from past experience that relays can be a real weak link and I was more than confident this was the problem.. I pulled the relays from the back up car.. popped them in an went for a drive. The car ran perfect.. problem solved !!!
I informed the GT tech and he was happy to be informed of this potential problem. If you have any roughness or drop off in power over 4000 RPM I would go straight for the relays. Even a slightly pitted relay can cause week voltage and erratic fuel pump operation.
So that's my long story.. I am happy to hear it was a quick fix for someone else..
BlackICE
GT Owner
Briain, a great story and detective work. Thanks for sharing.
This supports my theory that it is hard to work on modern cars without a wiring diagram. Sam will love this. I cannot find one for my 7 series BMW without buying a 30K tool! No wonder they depreciate so fast!
This supports my theory that it is hard to work on modern cars without a wiring diagram. Sam will love this. I cannot find one for my 7 series BMW without buying a 30K tool! No wonder they depreciate so fast!
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2112
Blue/white 06'
Is there a better relay than the stock relay?
I bought some expensive Hella relays for my boat........Chinese junk, at least these particular units. :bored
I bought some expensive Hella relays for my boat........Chinese junk, at least these particular units. :bored
Empty Pockets
ex-GT Owner
'Just curious, Brian: do you think taking an eraser to the contacts would have solved the problem w/o replacing the relays (at least for a while), or were the units themselves just SHOT?
(Yes, I know, guys - why bother. When you already have a $12 part removed - replace it. But, what I'm thinking is one MIGHT be able to just clean the contacts if this pblm shows up when one's 300 miles from nowhere during a 4 day holiday weekend.)
(Yes, I know, guys - why bother. When you already have a $12 part removed - replace it. But, what I'm thinking is one MIGHT be able to just clean the contacts if this pblm shows up when one's 300 miles from nowhere during a 4 day holiday weekend.)
Empty Pockets
ex-GT Owner
I have no idea. 'Hard to tell from the photo. That's why I was wondering about cleaning 'em.
STORMCAT
GT
Thanks buddy. Sharing is what makes this place so great. I'm happy to hear we resolved the issue for another GT owner
I thought about trying to find some new heavy duty relays but if they don't fit in the slots you've created some other issues to deal with. I've concluded it's probably just easier to replace them every 5000 to 7000 miles. They are a standard ford part so they should not get stupid expensive. As noted in my 1st post the new relays are stamped made in the USA : )
EP. The contacts were physically pitted. A points file would work but I had to destroy the relay to get at the contact points.. so that's a moot point. Being the curious cat I am I just had to get a look at the culprit that caused me so much grief !! : )
You can pop off the covers but the realys are really not serviceable..
BlackICE
GT Owner
If the wiring access is not too difficult and you are willing to modify your wiring harness, a Relay Snubber Circuit around the contacts can extend their life. I don't know if such a circuit is in the FPDM, but it should be.
http://www.electronics-tutorials.ws/io/io_5.html
http://www.electronics-tutorials.ws/io/io_5.html
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Empty Pockets
ex-GT Owner
vincenteveraert
New member
- Oct 12, 2010
- 1