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.
Scan Tool Data Definitions
- Battery Voltage Signal
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The scan tool displays 0-20 Volts. The scan tool displays the voltage as received by the Module or the 72-08 battery voltage message from the BCM over class 2 lines.
- Crank Request Signal
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The scan tool displays Yes/No. The scan tool displays No until the ignition is placed into the START position then Yes is displayed.
- GEN F-Terminal Signal
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The scan tool displays 0-100%. The scan tool displays 0-10% until the engine is started and the ECM receives a signal from the generator then OK is displayed.
- GEN L-Terminal Signal Command
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The scan tool displays On/Off. The scan tool displays Off until the engine is running, then the ECM supplies the percentage value varies depending on electrical loads
- Ignition 1 Signal
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The scan tool displays 0-20 Volts. The scan tool displays the voltage as received on the Ignition 1 circuit to the ECM.
- IMS
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The scan tool displays Park, Park/Reverse, Reverse, Reverse/Neutral, Neutral, Neutral/Drive 4, Drive 4, Drive 4/Drive 3, Drive 3, Drive 3/Drive 2, Drive 2, Drive 2/Drive 1, Drive 1, INVALID, and OPEN. The scan tool displays the physical position of the Internal Mode Switch (IMS) of the transmission.
- Starter Relay Command
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The scan tool displays ON/OFF. The scan tool displays Off until engine start has been requested, then it reads On.
- Starter Relay Control Circuit
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The scan tool displays Fault/OK/Invalid State. The scan tool displays Fault until the starter relay control circuit is grounded then OK is displayed.
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.