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 Does Not Communicate With Class 2 Device: Description
Modules connected to class 2 serial data circuit are monitored for communication during normal vehicle operation. Operating information and commands are exchanged between modules. Connecting scan tool to DLC allows communication with control modules for data messages, diagnostics and other information communications. DTCs may set due to symptom and during diagnostic procedures. Complete diagnostic procedure to ensure all DTCs are diagnosed and cleared from memory.
BCM detects that ignition is ON and sends appropriate power mode message to other modules. BCM must be connected to DLC for any other modules to communicate with scan tool. When class 2 serial data circuit is shorted to ground, DTC U1300 or U1305 will be set. When class 2 serial data circuit is shorted to power, DTC U1301 or U1305 will be set.
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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.
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