Anyone Familiar With A Breakout Box?

Discussion in 'Fox 5.0 Mustang Tech' started by scld1354, Jun 11, 2014.

  1. I'm troubleshooting some problems in an 88 gt. I bought a PCED for help. I knew ahead of time that the PCED references the breakout box and provides instructions on how to use the breakout box. I don't have a breakout box, and most of the results can be found by back-probing wire harness connectors.

    So here's my question. I'm at a spot now where the PCED instructs me to switch the PIP to OPEN and check voltage on a particular wire. What does switching the PIP to OPEN do? Is it something I can replicate without using a breakout box?

  2. The answer is no, not in any simple manner

    What was your original problem or post?
  3. You lost me at PCED
  4. PCED = powertrain control / emissions diagnostics. It's step-by-step instructions on exactly how to troubleshoot and diagnose things. Bad thing is you need a breakout box to follow the instructions.

    Jrichkler, you actually helped me out trying to diagnose the problem (

    It was originally a 91 code, but something happened and I am now trying to figure out why the car won't start under "normal" conditions. (I need 30* advance of base timing for the car to start and stay running.) The PCED has me testing the TFI module, and it looks like there may be a problem with the wire between pin #56 and TFI connector. (But I did check resistance between the EEC connector and the TFI connector, and there is literally NO resistance.) I am at a point where I need to "switch PIP to OPEN" and check voltage. Like I said, without a breakout box, I can't just switch the PIP to open. I was hoping someone would know what switching PIP to open does, so I can try and replicate it without using a breakout box.
  5. No resistance? Is that the description of an open circuit (meter leads not connected to anything) or a resistance less than your meter can display?

    If there is voltage present in a circuit under test, and you try to measure resistance, you will get weird results.

    Switching the PIP to open deprives the computer of timing information needed to calculate spark advance and injector timing.

    You might want to try disassembling the TFI wiring connector and temporarily remove the PIP wire from the connector shell

    Diagram courtesy of Tmoss & Stang&2birds

    Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs

    See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring Everyone should bookmark this site.

    Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs

    Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs

    Ignition switch wiring

    Fuel, alternator, A/C and ignition wiring

    Vacuum diagram 89-93 Mustangs

    HVAC vacuum diagram

    TFI module differences & pin out

    Fuse box layout

    87-92 power window wiring PowerWindowWiring.gif

    93 power window wiring
    #5 jrichker, Jun 13, 2014
    Last edited: Jun 13, 2014
    scld1354 likes this.
  6. Yah, I didn't mean zero resistance. Let me rephrase.... its the same amount of resistance I get when I touch the probes together, which on my meter is 0.03-0.06 ohms (when the meter is set to 20ohms resistance). I know the number displayed may not be entirely accurate, but like I said I get the same results when the probes are touching each other.

    That's what I'm talking about!!!! I'll try it out today and see what results I get.
  7. I think I see what the pced is trying to have you do. is it correct to say the no resistance measurement was between the ecu pin and the other test lead all the way out to the TFI? if so, almost no resistance means the wire is not cut, it is continuous from tfi to ecu. jrich has a good idea in taking the pin out of the TFI connector and letting the wire hang. The test will let you know if the whole TFI bundle got pinched and the PIP wire is now crushed into another wire or contacting another wire in the bundle. (called a metallic cross fault in the telephone industry)
  8. The breakout box was a rudimentary way to diagnose circuit problems before the days of live data streaming. It tee'd into the PCM connector and gave you an easy way to connect into any circuit you wanted. I worked for Ford back then and we almost never used it because it was time consuming and it was almost always quicker to just connect into the suspect circuit on the car. I'm not one to throw parts at a problem, but fwiw if you have a primary ignition fault it's most likely a failed TFI module. If that's what you find, get an O.E. replacement.
  9. Did the test today. I disconnected the PIP wire from the TFI connector, ran the test and had voltage within the acceptable range. I found out the PIP voltage originates at the TFI, not the EEC. Anyway, according to the PCED, there is a problem with the a PIP between the TFI connector and the EEC connector. I'll test with a new wire and see if that helps any.
  10. Here's an update..... It still doesn't work. I ran a wire directly from the TFI to the EEC, and it still won't start and run unless timing is advanced 30*. I'm out of ideas. Im thinking it has to be something electrical that just took a dump. There was no build up, no warnings, or anything like that. Mechanically, everything checked out. I don't just want to throw parts at it, expecially because everything is checking out OK.

    If it helps any, even though it will start and run at 30* btdc, it runs like crap.
    #10 scld1354, Jun 21, 2014
    Last edited: Jun 21, 2014
  11. Got access to a replacement computer?

    The stock speed density 88 uses one of these two computers:
    1988 MANUAL 8LD
    1988 AUTO 8LF

    88 Californa cars use MAF:
    A9S - 88 5.0L Mustang California Mass Air
    #11 jrichker, Jun 22, 2014
    Last edited: Jun 23, 2014
  12. I may be able to borrow one. It will be a few days, but I'll post results.
  13. Its a Mass Air car. I can't remember the computer code off the top of my head. If I understand your post correctly, the 8LD and 8LF EEC's can be used for both Mass Air and for Speed Density????
  14. That's a typo on my part, which I have corrected....
  15. In addition to performing the tests outlined in the PCED, I swapped in a known good distributor (known good TFI and PIP), and the car did the same thing. So, I am looking at getting a EEC I can swap out.

    I found an 8LG locally for a good price. According to a post found by Noobz347, the 8LG will work. Here's the list Noobz posted....

    8LD= 88 5.0 HO California Automatic
    8LG= 90 5.0 HO California Automatic
    A3M= 89 5.0 HO T5
    A3M1= 92/93 5.0 HO T5
    A9L= 89/92 5.0 HO T5
    A9M= 89/93 5.0 HO T5
    A9P= 89/92 5.0 HO Automatic
    A9S= 89/92 5.0 HO California T5
    C3W= 91 5.0 HO Automatic
    C3W1= 92/93 5.0 HO Automatic
    D3D1= 91/93 5.0 HO Automatic
    J4J1= 94/95 Cobra
    PC1= 85/86 SVO
    PE= 85/86 SVO
    PF2= 87/88 Turbo Coupe T5
    PF3= 87/88 Turbo Coupe T5
    PK= 87/88 Turbo Coupe Automatic
    PK1= 87/88 Turbo Coupe Automatic
    S0Z= 89 5.0 HO Automatic
    T4MO= 94 5.0 HO T5
    U4PO= 95 5.0 HO T5
    W4HO= 94/95 5.0 HO Automatic
    X3Z= 93 Cobra
    ZAO= 94/95 5.0 HO T5
  16. Please update if you got it fixed i'm currently having the same problem
  17. I highly suggest that you start your own thread and include all the details about your car: year, model, mods, current problem and anything else unique about your car that may be relevant to the problem you are having.
  18. I did and everyone keeps telling me to check the balancer though I've said its good (checked by a shop) and mentioned that my car stalled and that i had to advance it to 30* to run afterwards when it had run for months before hand.. Timing/drivability Issues | Mustang Forums at StangNet
  19. The 88 and 90 California cars are Mass Air. Their EECs are interchangeable with an A9L or A9S.

    The EECs that are NOT interchangeable are the Speed Density EEC with Mass Air EEC.

    The list that you posted shows what came in which years. If you have an auto, I would stick with an auto computer and vice versa when possible. If you have an auto, you should be able to use any 5.0 auto EEC.

    If you are going to chip tune the EEC then it's a moot point however... an 8LD or 8LG is not going to provide you with the same level of performance as an A9L, A9P, or A9S without being modified.