93 Silverado Trouble Codes 42 & 54 HELP

Discussion in 'General Chevy & GM Tech Questions' started by lancer, Nov 1, 2010.

  1. lancer

    lancer Epic Member 5+ Years 500 Posts ROTM Winner

    hey guys my new truck has had the service engine light come on and i did the jumper wire to get the codes and the code numbers i get are 42 and 54. i went by the local parts store to see if they could tell me what they were but they are not very bright (small town). i looked them up on google and got ELECTRONIC SPARK TIMING (EST) CIRCUIT for code 42 and FUEL PUMP CIRCUIT (LOW VOLTAGE) for code 54. can ANYONE help me with what these mean or what may have caused these codes to pop up or what i should be looking for. i've only had the truck a few weeks and i'm still trying to get all the bugs out of it. :grrrrrr: sorry guys i also forgot to mention that i can drive it for maybe 15-20 minutes before the light comes on.
    Last edited: Nov 1, 2010

    99'HEARTBEAT MODERATOR Staff Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    For a Code 42...Electronic Spark Timing Cricuit,
    Trouble Code 42 indicates that there may be a malfunction in the Electronic Spark Timing (EST) system.​
    During cranking, the timing is controlled by the ignition module while the ECM monitors the engine speed. When the engine speed exceeds 400 RPM, the ECM sends a BYPASS signal to the ignition module which switches the timing to ECM control. The ECM calculates what the timing should be then "tells" the ignition module via the EST circuit.​
    An open or ground in the EST circuit will stall the engine and set a Code 42. The engine can be re-started but it will run on ignition module timing.​
    The conditions for setting this code are:

    • System in BYPASS mode but the ignition module is still controlling timing
      - or -
    • Engine speed > 600 RPM with no EST pulses (ECM controlled timing) going to the ignition module for 200 msec.

    Typical causes for this code include:
    1) BYPASS line is open or grounded
    2) EST line is open or grounded
    3) PROM or CALPACK not seated properly in the ECM
    4) Poor connections between ignition module and ECM
    5) Poor routing of EST harness and/or poor quality ignition wires (EMI induced electrical noise)
    6) Faulty or incorrect ignition module
    7) Faulty ECM​

    For the Code 54
    ...Fuel pump Cricuit.
    CODE 54
    If this code appear, it is probably due to a loose connection or bad ground. If a computer is connected to the car's ALDL connector when the code appears, check the computer cable connections.​

  3. MightyMax

    MightyMax Rockstar 100 Posts

    For the 42 (EST) error, look for a single wire (brown I think), that might be disconnected or maybe the insulation has come off and is grounding to the frame.
    Not sure the location on a '93, but on the '91 models it was between the engine and firewall, running along the firewall.

    For the Fuel Pump, I would check the connector and grounding wire that is back by the tank, along the frame.
    73_Electraglide likes this.

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