Fuel Delivery or PATTS?

Discussion in 'SN95 4.6L Mustang Tech' started by reddmann, Dec 1, 2012.


  1. reddmann

    reddmann New Member

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    I inspected around the PCM earlier, no signs of rodents, chewed wires, turds, hell there was hardly any dust. Everything is in real good shape with this car. When you say it could be the CJB itself, are meaning that the wires coming off of F2.2 and F2.8 could have came loose off the back? Im going to go ahead and buy a new ignition switch, hell there only 11$ and I gotta get this thing on the road. I went back over all the fuses testing EVERY ONE with a testlight and found nothing. I will replace the ignition switch, get a set of Wiring Diagrams, and test the wires on the back of those fuse blocks and post results. When i say this car is in good condition, it literally looks like its been wrapped in plastic since 99, thats why i dont see it being an electrical issue somewhere in the wires but i will check. Gotta get this thing going.
     
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  2. reddmann

    reddmann New Member

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    You know one thing i have failed to mention about all of this, the reason i replaced the fuel pump is because i had power going in and out of the IFS and power to the plug by the center of the tank. After replacing the fuel pump now i do not. lol There is just some things that doesnt make sense, like how do you have power to something, replace something downstream and put it back together and not have power the next. All i did was unhook the battery for crying outloud.
     
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  3. wmburns

    SN Certified Technician

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    I believe elsewhere in this thread I said to check the battery, battery terminals, and grounds. That includes the grounds around the radiator core support.

    There are also two large single wire connectors with a black wire with white stripe. These ground the PCM and CCRM. A weak connection here could cause all sorts of problems. They are located down low on each side of the radiator core support.

    If after replacing the fuel pump there isn't power into the IFS switch, then it seems likely to me that something happened during the repair. One possibility is a pinched wire at the fuel hat or on top of the gas tank. Also there are TONS of always on circuits on today's cars. Did you disconnect the battery negative while doing the work?

    Have you confirmed the fuel pump works by powering directly?

    Have you actually CONFIRMED all of the fuses in the BJB? Including confirming there is power on the INPUT side of the fuse?

    Honestly, there are some very strange and unusual symptoms here. If this were my car, I would take a step back and repeat some of the tests that are the bases of the trouble shooting decision tree. Why? Because a wrong test result can set up a wild goose chase!
     
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  4. reddmann

    reddmann New Member

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    So i took your advice, the very first thing i did was make sure the grounds were good. I took the ones from the radiator support off, scraped and cleaned, and put back on. Then i went back to the inertia switch to check for power again. I DO have power to both sides of the switch with key on. So then i went down to the plug by the tank. With key on i got a DIM light, and a BRIGHT light. That was the only two points that had power.. This was the reason i replaced the pump to begin with. I did disconnect the power before working on Everything. I have not tried to test the pump direct yet because i dont want to mess anything up, quite frankly i dont know how. In the BJB, with key on there should be power to every input correct? If there IS power at IFS, that shows a GOOD CCRM correct? Nothing changed with the New ignition switch. Same ------ on odometer, with the fan going.
     
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  5. wmburns

    SN Certified Technician

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    FWIIW, the 99-04 Model year uses the return fuel system. The PCM controls fuel pressure by varying the power out of the fuel pump driver module. So it would be NORMAL to see variable voltage from the FPDM to the fuel pump.

    Having power at the IFS switch does prove that the fuel pump part of the CCRM is good. It does NOT prove that the part of the CCRM responsible for the PCM is working. Remember there are separate relays in the CCRM for PCM, fuel pump, high and low speed fan, and AC clutch.

    BUT..... since you have confirmed power to the COP red wire, this confirms the PCM/ignition part of the CCRM.

    Given the strange state of circumstances, recommend inspecting the CCRM electrical connector for evidence of overheating or water damage.

    Look at the wiring diagram and test all outputs from the CCRM. If all CCRM tests are good, it's time to start considering the possibility of a bad PCM. Have you attempted to connect an ODB2 scan tool? Does it talk?
     
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  6. reddmann

    reddmann New Member

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    Well i hooked up a Scan tool and did not link up. It has power just not linking. oh well, another tool in the toolbox i guess.
     
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  7. wmburns

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    Based upon:
    • power at the IFS switch with key on (proves CCRM)
    • power at the COP red wire with the key on (proves CCRM)
    • All dashes in the cluster (indicates the cluster does not "see" the PCM).
    • Cooling fan running all the time. (indicates the CCRM does not "see" the PCM).
    • Battery cables clean and tight.
    • all fuses confirmed good.
    • all radiator core support grounds clean and tight.
    • No communication with ODB2 scan tool (indicates that the PCM is not functioning).
    • No evidence of water or rodent activity in the area around the PCM.
    IMO it's either a broken/bad PCM ground or a bad PCM.

    So unless you have disconnected either one of the two large black wires with white stripes, it's time to consider a bad PCM.

    However, it's not a bad idea to confirm there aren't any burned/bent/pushed pins at the CCRM just to be certain.
     
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  8. reddmann

    reddmann New Member

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    This is where i post pics of the car burning. lol jk. If i was to order a PCM from the parts store and put it on the car would it work? Or does a thing like this have to be programmed to the car itself. I know i hear about guys putting tuners on there rides which disables the PATS. If this is the case, do you have any suggestions of one? Sometimes in life you just have to spend money i suppose. Hey i do appreciate you taking your time helping me trouble shoot this. Im gonna go check those Black and white wires, and if thats not it then start looking at a PCM swap. ehhhh.
     
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  9. reddmann

    reddmann New Member

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    Well, FINALLY got the chance to go out, pull the PCM and inspect EVERYTHING again. No loose grounds, nothing. Took it to a shop nearby and the first thing he tells me is it seems to be the PATS. lol.. I think just from what ive learned on this forum alone i know more about troubleshooting this thing than he does.
    We will see and i will post whats up when i hear something for other readers.
     
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  10. reddmann

    reddmann New Member

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    Burns, took the car to a Mech. Indeed it was the PCM, 750$. He said what could could have caused it to just go bad was me having the car jump started a numerous amount of times in a role. Said not to do that because of power surge. But yeah its fixed, Speedometers off 10 now, but she runs like a charm.
     
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  11. SLIMS5.0

    SLIMS5.0 New Member

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    I now it's been a little while but I'm having same issue but my car still runs theft light is on all dashes no tach speedometer or temp gauge when there is all dashes sometimes flickers for a sec or two shows the milage then dashes I've tore this car apart I'm thinkin PCM but not sure cause it comes an goes but is gettin worse hand held wouldn't read codes but my buddy got in to the PCM finally with his fancy snapon scanner an cleared all an was fine for three days now back to dashes an gauges not workin when the engine light kicks on is when the problems happen as long as engine light is off everything is fine I was told to replace GEM box didn't help lol
     
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