1997 cranks no start. ecm no read unless cranking

Lincoln Mark VIII

  1. hhiibel

    hhiibel New LVC Member

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    my ecm will not connect to reader unless i'm cranking. no codes. it won't start. i have fuel pressure. switched starter and ecm relay. same thing. got reman ecm. same thing. traction control off light is on. to recap, plug in reader, put key to on and reader will not connect. start cranking and it connects. does this ring a bell? is there some 'sensor' i should disconnect? or whatever...? i've been a few years with no air ride. springs now. prior to this, i was solving no start by putting in new ecm relay. Now i've gone back thru some i replaced and they are good. I've powered duel elect. fan with them. one is in starter relay even now. but had to add this as it is what was going on leading up to this. no start. no read. so if you got something to try let me know... thanks. i can't even remember how reader used to connect, but doesn't it only need key in? or key in first position? or does it even need the key in?
     
  2. germansheperd

    germansheperd Active LVC Member

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    Crankshaft position sensor is generally a replacement part from what you are describing. I can not tell you if it will not let your ECM connect to a reader?
     
  3. joegr

    joegr Dedicated LVC Member

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    It sounds like the ECM is not being powered when the key is in the run position, and instead is only powered in the start position. This should be very easy to test and verify with a multi-meter. From there, you can verify if it is the ignition switch itself (not uncommon), or somewhere else.
     
  4. hhiibel

    hhiibel New LVC Member

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    joegr, yes that's what drifted into my head while trying to sleep last night. i guess i came to having an extra ecm because i didn't want to dive into wiring.... oh well. i will first see if i have signal to relay. thanks.
     
  5. hhiibel

    hhiibel New LVC Member

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    ecu relay is being activated. still no datalink connect unless cranking the engine. i have all the grounds and powers at ecu connector marked. was wondering if its valid to measure the pins with ecu disconnected. i don't want to probe the wires unless its the only way. i poured over schems long time ago and marked things. I did check pin continuity. now i guess its time to see live readings. 71 and 97 are fed from relay. 55 is 12v constant from fuse 1 under hood. 13 is eprom power to datalink pin 13, 16 is datalink power/data link pin 2 from fuse 38 inside, 15 is datalink ground datalink pin 10. all fuses are good. c'mon rack your brains, this must be caused by something. some sensor or switch. anywho...i'll measure live probe i guess. anyone want a car?
     
  6. joegr

    joegr Dedicated LVC Member

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    You need a load (like the ECM) to verify that the circuit is really supplying enough current. Short of that, you could measure voltage while using a test light at the same time.
     
  7. hhiibel

    hhiibel New LVC Member

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    readings from ecu pins. key in run.
    55 - 12V
    16 - 0.51V
    3 - 0
    15 - 4.6
    13 - 0.5
    24 - 0
    25 - 0
    51 - 0
    77 - 0
    97 - 11.5
    71 - 11.5

    97 & 71 are pwr to injectors
    55 is under hood fuse 1. const power
    15 is pin 10 on datalink
    16 is pin 2 on ecu
    13 is pin 13 on datalink, is eeprom
    all ecu zero reads are grounds.

    datalink
    pin 10 - 4.6 run, 4.6 cranking
    pin 2 - 0.5 run, 0.5 cranking
    pin 13 - 0.5 run, 0.5 cranking
    pin 16 - 12v const
    pin 7 - 10.6 in run, 8.5 cranking.

    'check traction control' on dash
    'trac control off' at info center.
    check eng. at info and dash.

    reading senses SAE J1850 PWM in run. just never links till crank.
    note, key in run no connect, but turning key to off, it gets a connect. of course it won't stay reading.

    so in the market for a very low mile town car at a private seller price.
     
    Last edited: Aug 27, 2019
  8. joegr

    joegr Dedicated LVC Member

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    Really weird...
     

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