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P codepowertrainMedium severity

P0617Starter Relay Circuit High

The starter relay control circuit is stuck at a higher voltage than the engine computer expects.

Definition

The PCM watches the starter relay control circuit for plausible voltage levels, and P0617 sets when the circuit reads high when it should be low — commonly from a short to battery voltage, an open circuit that floats high, or a crank request input that stays active. On GM trucks this code is well known for setting when a worn ignition switch or ignition lock cylinder holds the START signal on after the engine is running. Symptoms range from none to a no-crank, slow disengagement of the starter, or in severe cases a starter that stays engaged and is destroyed.

Common causes

  • Worn ignition switch or sticking lock cylinder holding the crank/START signal high (common on GM trucks)
  • Starter relay control wire shorted to battery or ignition voltage
  • Open circuit in the control wire allowing it to float high
  • Corroded relay socket or spread terminals creating high resistance
  • Faulty starter relay
  • Faulty PCM driver circuit (least common)

Common misdiagnoses

  • Replacing the starter motor when the ignition switch is holding the crank signal
  • Replacing the starter relay repeatedly without finding the short to power
  • Replacing the PCM before testing the ignition switch START circuit
  • Replacing the battery or cables for a control-circuit voltage fault

Troubleshooting steps

  1. 1.Check the crank request signal after start-up

    Watch the ignition START/crank request PID on the scan tool with the engine running; if it stays active after the key returns to RUN, suspect the ignition switch or lock cylinder.

  2. 2.Measure the relay control circuit voltage

    Backprobe the control terminal key-on: voltage above the specified rest level (often full battery voltage when it should be near 0 V) confirms the high condition.

  3. 3.Test for a short to power

    With the relay and PCM disconnected, check the control wire for voltage from other circuits, inspecting harness sections that run with ignition-fed wires.

  4. 4.Inspect the relay and socket

    Look for burned or spread terminals in the relay socket and bench-test the relay's coil and contacts.

  5. 5.Repair and confirm over multiple key cycles

    After repairing the switch or wiring, clear the code and verify the crank signal drops out immediately after each start, since a lingering signal will keep re-setting P0617.

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