Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Run/Crank Relay: Notes
The run/crank relay control circuit is connected to a constant ground and is switched by the ignition 1 circuit or the BCM. The BCM, will in lieu of the ignition switch position, activate the Run/Crank relay during a remote start event. The Run/Crank relay supplies a power signal to the following circuits, when the a Run or Crank power mode is selected:
- Automatic transmission shift indicator
- Automatic transmission (A/T)
- Switched power feeds to the BCM
- Electronic brake control module (EBCM)
- Electronic ignition module (spark control)
- Electronic power steering module (EPS)
- Fuel injectors
- Powertrain control module (PCM)
- Park neutral position (PNP) switch
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.