2004 no fuel pressure
Thread Starter
Burning Brakes
Joined: Oct 2004
Posts: 801
Likes: 17
From: Middletown Delaware
2004 no fuel pressure
04 will not start no fuel pressure. I jumpered pin 30 to 87 at relay and pump runs 58 psi. I cleaned ground at left rear wheel and left side of block. cannot find sp122 grounds under battery. Pin 86 shows 12v pin 85 shows good ground. What is my next step? Appears pump is not being told to turn on. Ignition switch?
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,621
Likes: 4,066
From: Cape Coral, Florida
Here is a YouTube video I did a few weeks back (subscribe and ring the bell)...hope it helps !!....you should check pin 86 with 12 volt test light...you'll see why...with relay removed you were reading a bias voltage on pin 86 as I explained in the video !!...the test light should light for 2 seconds and go out with key ON !!...if test light doesn't come on you may have an open in the wiring between the relay control at the PCM and pin 86 or a bad connection at the fuse box itself...you should then check if you have 12 volts at the PCM end...now in your case you read 12 volts at pin 86 so we know there is no open or short in the wire but instead you are not getting that fuel enable signal.from the PCM !!...on your '04 it's pin 9 (dark green/white) at the C2...the green harness connector...SP122 might be taped to the harness...you have to remove the 4 bolts at the battery tray !!...I always use a "load light" instead of a 12 volt test light to check grounds....didn't use it in the video because more people have 12 volt test lights !!...also I didn't show it in the video but I used a "non resistor" key in the ignition and the fuel pump still primed !
Last edited by C5 Diag; Apr 11, 2019 at 03:53 PM.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,621
Likes: 4,066
From: Cape Coral, Florida
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,621
Likes: 4,066
From: Cape Coral, Florida
Yep !!...you were reading that bias voltage with the multi meter...it can really mess you up on a fuel pump relay diagnosis...let us know what you see with the test light...did the car run with 87 and 30 jumpered ??
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,621
Likes: 4,066
From: Cape Coral, Florida
Hi Dave !!
I'm assuming you swapped relays...say the horn for the fuel pump...if you did look see if you have any DTC's stored...specifically a P1626 and or any "U" codes...if any U codes there may be some comm issues between the BCM and PCM...do you have a scan tool ??...will help in case it is not anything except for the VTD system....did you try another key ??...does the security light goes out ??...with a scan tool it will help if you can try to communicate with the BCM and PCM....also check BCM fuse fuse 13 and PCM fuse 16....ignition switch ??...maybe ??...if you have a multimeter hook positive lead to battery positive and the negative lead to one of the test points on top of fuse 13 and then check fuse 16....voltage drop across the ignition switch should be less than .1 volt while the engine is CRANKING !!...also exactly HOW did you confirm that Pin 85 (ground) was "good ground" as you say ??...visual inspection, multmeter, or a 12 volt or a load light with an old headlight bulb as pictured !!
EDIT: see if you have 5 volts at the MAF sensor signal wire...yellow wire !!
Last edited by C5 Diag; Apr 11, 2019 at 04:16 PM.
Thread Starter
Burning Brakes
Joined: Oct 2004
Posts: 801
Likes: 17
From: Middletown Delaware
test light lit for 2 seconds. All circiuts ckecked out problem was pin retention in fuse box for relay. For info I don't think 2004 has the sp122 block it does not show up in the wiring diagram I have . Thanks for all your help.
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