97 gmc 4.3 electical problems

Discussion in 'GM Electrical Tech' started by buddy95, Jan 5, 2013.

  1. buddy95

    buddy95 New Member

    i have a 97 gmc 4x4.have replace motor and bout all the sensors.now having an electrical problem.some sensors test good with test light and some dont....really need some help please
  2. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    I think that we may need some more information! What sensors are testing bad? How are you testing them with a light? Not all sensors will test "ok" with a test light. What codes are you getting? The codes could help track down the issue.
  3. a.graham52

    a.graham52 Rockstar 100 Posts

    x2. we need to know what your issue is
  4. donyms

    donyms Epic Member 5+ Years ROTM Winner 1000 Posts

    Welcome to the club, it's good to have you here. :glasses:
  5. mfleetwood

    mfleetwood Epic Member 5+ Years ROTM Winner 5000 Posts

    I moved your thread to the correct forum section and enhanced your thread title so that it more describes the category of problem you are having.

    Welcome to the Club and good luck in getting your issues solved.
  6. buddy95

    buddy95 New Member

    getting codes for oxygen sensor and catalyst not ready,truck runs great untill its warmed up.cruising around 60 mph then it jerks
  7. rileyjr16

    rileyjr16 Epic Member 5+ Years 1000 Posts

    You replaced the o2 sensors?
  8. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    When cold, the PCM uses a programmed set of fuel/air mix instruction tables (open loop). When the engine gets warm, the PCM switches to the O2 sensors to tell the PCM the ratio that is needed (closed loop).

    If it runs "bad" when warm, you probably need new O2 sensors (just the front ones, the rears are to test the cat).
  9. shibby2oo8

    shibby2oo8 Member 2 Years 100 Posts

    The heater circuit may be bad or crossed signal wires, scan it when running bad and go to data and tell us the voltage of the upstream (1/1,1/2) sensors. They should bounce up and down consistantly. You can use a light to test the heater circuit but DO NOT , repeat DO NOT SHORT THE HEATING AND SENSOR CIRCUITS, WILL FRY THE COMPUTER! What i use is a low beam headlight with socket to test both power and load test the wires, if it starts bright then dims there is a bad connection somewhere, no light no power.

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