Another electrical issue please help

Discussion in '2005+ Mustang GT 4.6L Tech' started by swflastang05, Feb 4, 2017.

  1. swflastang05

    swflastang05 Back for More

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    I started my car this morning and left to go for a drive, like I always do on the weekend, I got a few blocks away and it smelled like something was burning, so I turned around and went home and found a fuse holder melting down and the wire burning in the trunk next to my battery. The fuse holder and wire connects to the alternator. I didn't find any issues with the wire, etc. so I replaced the fuse holder and tested it, all seemed to be okay. I think maybe the screw that held the fuse holder to the wall rubbed through the insulation and grounded out the wire. Afterward I left again to go on that ride I started earlier, all seemed fine. Then on my way back home I did a real short 3rd gear pull, maybe for 2 seconds max, and again all seemed fine but a few seconds later when I went to give it more throttle it was acting like a plug was fuel soaked. I continued to drive it easy, I've had this happen before and it normally cleans out and is normal again after a minute or so of driving, but not today. Got home and pulled the DTC's (no CEL though) found P0689 - Electronic Control Module Power Relay Sense Circuit Low, P0830 - Clutch Pedal Switch A and P0833 - Clutch Pedal Switch B. Well my car was originally an automatic, and still is, although the ECU thinks it's a stick since I have a 4r70w with MVB. So the motor runs okay but when you get into the throttle it starts breaking up, once I tried to stay in it to see if it would clear up and it leaned out and my LPM cut it off, that procduced another code P0171 bank 1 lean. I checked all the grounds, swapped PCM relays with no luck, any suggestions? I also checked all the plugs and they all look fine. I'm stumped with this at the moment, I don't know if that wire melting issue from earlier is related or not.
     
  2. BruceH

    BruceH BBB Big Bore Boss 322 Staff Member

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    I would guess that something is completing a path to ground intermittently. I know, quite obvious but the big question is what? Is there any chance that something (maybe the motor or headers) can move enough under load to cause a temporary short?

    You have a big power setup that transmits the power to the ground well. Anything that's not hard mounted to the chassis is going to move and possibly create a path to ground if it has unprotected electrical power.

    I'd start with the obvious, looking for anything that can move or flex under power and insuring there isn't a chance it could make contact with power or ground. I'd bet that you already have done that though.
     
  3. redfirepearlgt

    redfirepearlgt forum member

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    I would begin by inspecting all wiring between the battery positive terminal and the main 12vdc feed to the BEC under the hood. This wire unmodified is a red wire labeled as 2037 and goes form the positive post of the battery to Connection C1035-A1 on the BEC. Inspect the associated wiring with regard to factory and your battery relocation modification for burns, or chaffing elsewhere in the run that could create low resistance to ground (not a complete short to ground). Then check the actual voltage at C1035-A1 on the BEC. Next inspect the BEC itself for burns or damage related to the initial issue you found. Also check F40, F42 in the BEC to see if they are blown. Hopefully this is an issue related to teh battery relocation and will be fixed by repairing the associated wiring. Worst case it could be a BEC and/or PCM IMHO.
     
  4. swflastang05

    swflastang05 Back for More

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    Yes I've spent a few hours looking for this type of stuff and came up with nothing. There really isn't anything that can move much in my car, wiring wise.

    I traced both battery connections, from chassis ground and all the way to the bec and there are no signs of any issues anywhere. All fuses are good, I took apart the bec and all the harnesses, everything looks the same as it did previously. I found a few semi-loose connections at various locations but tightened them down and test drove with no change in the condition. It almost acts like there's an issue with the MAF sensor. I actually was expecting to find a SC tube blown loose or something when I got home, but those all look good. That's what it's running like though, as if there's a discharge tube loose or an issue with the MAF. I wonder if a bad MAF can cause those DTC's? I'll go for another drive tomorrow morning and data log this time to see what's going on, I'll send the log to Manuel maybe he'll see something that can point me in the right direction.
     
  5. redfirepearlgt

    redfirepearlgt forum member

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    The P0689 is the one I was focusing on. That is my main concern. If the PCM relay is energizing and the PCM and SJB are getting good power routed to them via C0135B-D5 and C1035A-B6, and all wiring you had problems with. The code 689 code has been used fora variety of different failures on Fords over the years in different models if you google it for more information. It's likely a limp mode code as well. Try resetting the PCM and reflashing it if you haven't done so again. Verify the voltage is actually good coming off of fthe alternator when the car is running. Also make sure that the alternator is putting out an abundance of AC ripple which would indicate the AC/DC rectification circuit in the alternator is bad. As a last measure and I hate to say this it may be a bad PCM if all voltages are good and the PCM relay is functioning properly. I look to the PCM as a possibility because of the erroneous clutch pedal codes which are not directly in circuit with the PCM relay. Often times when random diagnostics failures on CPU controlled equipment of any kind occurs its a power or CPU failure based issue. Would love to hear other opinions on the issue and/or your results when you find the culprit. Good luck.
     
    Last edited: Feb 5, 2017
  6. swflastang05

    swflastang05 Back for More

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    First, thank you very much for all the valuable information! I agree the PO689 is concerning. Please clarify for me the location of the C0135B-D5 and C1035A-B6 pins, are those on the PCM (engine computer)? Are they labeled? Or is there a diagram somewhere I can reference? I have verified there is 12 volts at both the battery and the main power wire connection at the bec (large fuse box originally under the hood), and close to 14 volts with the car running. I put my meter on a/c and connected to the battery and it was about .07 volts. I would assume the PCM relay is switching since the car does run and drive, it just breaks up as rpms increase.
     
  7. swflastang05

    swflastang05 Back for More

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    I just tried a different battery, and re-flashed the ECU, neither made a difference. The only DTC code I have now is the P0689 though.
     
  8. redfirepearlgt

    redfirepearlgt forum member

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    They are connectors on the BEC block under the hood. Pin D5 on Connector C1035B will be two red wires. Pin B6 found on Connector C1035A will have two wires colored Gray w Orange stripe.b The red wires also labeled wires 1118 received fused power from Fuse F40 feed the SJB. The Gray w Orange Striped wires labeled 1856 on the prints receive fused power from F42 and feed the PCM.

    Here is a link to the wiring diagram I am referring to. I just checked teh link and it works. When it opens grab the scroll bar on the drawing itself and scroll down to page 5 of 18. You will see teh PCM relay on teh BEC and the associated wiring. Don;t forget to make sure that when the key is on the PCM relay is being energized by the PCM as well. The PCM will sink the coil to ground with key on via pin E4 of Connector C1035A. Hope this helps man. I would hate to see this cost you that TS run at NMRA Bradenton.

    Both connectors C1035A and C1035B should be on the RH side under the hood on the BEC module.

    http://iihs.net/fsm/?dir=40&viewfile=Power%20Distribution-SJB.pdf
     
    Last edited: Feb 5, 2017
  9. swflastang05

    swflastang05 Back for More

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    Thanks, I ran into another road block though, my car doesn't match these schematics. For example D5 on 1035B is empty, but C5 seems to be the wires in the diagram. F5 matches the wires in the schematic, however there is no gray / orange wires anywhere in any harness at my bec. The relays are definately clicking though when I turn the key on, there's no question about that and since there is full voltage going to the bec most likely it's another issue, possibly the ECU / PCM. I hate to drop that kind of money on a part though and just hope that it fixes the problem. This is how my luck goes..

    And yes, my thoughts exactly, just when I'm getting ready to compete in an event I run into this BS! And it's a stupid problem, one that's not easily fixed since it's so difficult to troubleshoot.
     
    Last edited: Feb 5, 2017
  10. BruceH

    BruceH BBB Big Bore Boss 322 Staff Member

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    This is a general idea. Grounds. Is there any chance that a major ground has become corroded or loose over time? It wouldn't hurt to take the major grounds apart and clean them.

    Off the top of my head there is one on the back of the drivers side head, the main battery, one on the passenger side motor mount, and another near the cowl on the drivers side.

    Something to think about and it wouldn't take more than an hour or so to disassemble, clean, and reinstall these grounding points/cables.
     
  11. swflastang05

    swflastang05 Back for More

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    A recorded a data log today, looking at the voltage on that it reads 13.5 - 14.0 the entire time, would that be a reading from the PCM / ECU? Maybe a way to confirm it's not a voltage issue, since the wires in my car don't match the diagrams?
     
  12. swflastang05

    swflastang05 Back for More

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    I already checked the main battery cable ground, I'll redo the others too thanks Bruce.
     
  13. redfirepearlgt

    redfirepearlgt forum member

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    Sorry those schems don't appear to match your car. They are supposed to be Ford Tech manual wiring diagrams. A member has a link on line here that I was given for Ford service shop tech manuals for 2005 and 2011. In fact I think it was Bruce that provided me that link and it has been pretty useful with no wire code conflicts until now. IN fact i had a paper set of these manuals when I had my 2005, and they were awesome to have around for doing upgrades and so forth.

    If the car starts and runs, and the DTC's reset after clearing and did not return, they may have been created by the low resistance to ground you experienced originally if all wiring and voltages you are checking are good. So if those codes have not returned when you do a DTC scan again, I would call this good and chalk it up as part one resolved of a two part problem.

    Now its merely chasing down the load up problem you are having. Datalogging this issue that leaned out may be the answer to getting you closer to this issue with the help of your tuner. I'd also explore what Bruce is eluding to with regard to your throttle up issue. If I can help you find anything else feel free to PM or post back up. Either way would love to hear the outcome.
     
  14. swflastang05

    swflastang05 Back for More

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    Thanks for all the help again, I checked all the grounds, didn't find any obvious issues, I haven't test drove it yet but I'm not very confident that it's fixed. It's just my luck that those schematics are different than my car.

    Both clutch pedal codes are back now also, I'm leaning toward PCM / ECU. Hopefully I'll hear back from Manuel tomorrow and see what he thinks after reviewing the data log. I'll post up the results and outcome, whatever it turns out to be.
     
  15. redfirepearlgt

    redfirepearlgt forum member

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    why that it I have no idea. I sure wish I still had the paper version of my 2005 tech manuals to compare with. I gave them away when I bought my 2013 to a guy at work who still has his 2006. I've since changed shifts so I never see him much these days.
     
  16. 05stroker

    05stroker Never enough power guy!

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    I have a Ford wiring diagram manual at home. What pages eould yoy like? PM me your cell and I can text the page photos to you tonight.
     
  17. swflastang05

    swflastang05 Back for More

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    Does the case of the ECU need to be grounded? I saw in one of the schematics it references a case ground but my case is not grounded. I did try grounding it temporarily but it made no difference. Just wondering if I should make a permanent ground for it?
     
  18. BruceH

    BruceH BBB Big Bore Boss 322 Staff Member

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    http://iihs.net/fsm/ is the link.

    Louie in Dubai (G.T. on this forum) hosts the site. For those who don't know about Louie he runs a speed shop in Dubai. His shop mostly mods the rare European cars we drool over.
     
  19. swflastang05

    swflastang05 Back for More

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    Thanks Billy! I'll PM you if I need that.

    Thanks Bruce, I think that's the same link from above, that doesn't match my cars wiring.

    Update: I did some more testing and this is what I've learned so far. I went right to the power and ground wires on the ECU which are pins #35, #36 and the bottom 4 pins are ground. All 4 grounds tested good as well as both power wires. They have about 14 - 14.2 volts DC when driving. I did however check for AC voltage and found both of those wires have .424 volts AC at the time my motor breaks up. I don't know what's considered an acceptable level of AC voltage but I know it's not much, does anyone here know? Also that number spikes when starting the car to .8+ volts AC and almost 4 volts AC when shutting it off. I'm wondering if the alternator was damaged when that wire grounded out resulting in too much AC voltage and messing up the ECU, since that is the exact wire I had the issue with. I've researched others that have had that issue with the same DTC I have. Manuel said he didnt see anything weird in my datalog so no luck there. Just for shits I'm going to install a new set of spark plugs tonight too and see if that makes any difference.
     
  20. swflastang05

    swflastang05 Back for More

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    I got it! I installed a new set of spark plugs and went for a drive and sure as shit that fixed it! WTF! How the heck did one or more bad spark plugs cause all those DTC's? IDK but it's fixed now! I do still have those DTC's though for some reason, even after clearing them. I know some codes won't go away entirely with just a clear command, maybe I'll try to reflash it again and see if that takes care of it. Either way, the car is running great again! Thanks for all the help with this! Who would of thunk freakin' spark plugs.. Or actually that was one of the first things that came to mind, but I didn't think spark plugs would cause those DTC's. In any case thanks again all!
     

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