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.
Troubleshooting - B-CAN System Diagnosis Test Mode D
Do this diagnosis if a component that is controlled by the B-CAN system does not work or come on.
- If the component does not turn off or stop, go to B-CAN System Diagnosis Test Mode C (see TROUBLESHOOTING - B-CAN SYSTEM DIAGNOSIS TEST MODE C ).
- Seethe B-CAN system unit input/output index for a list of input and output devices and the control units that monitor the input and control the output devices (see HDS INPUTS AND COMMANDS ).
- Check the fuse of the malfunctioning output device.
Is the fuse OK?
YES -Go to step 2.
NO -Replace the fuse, and recheck.
- Check for DTCs by selecting the TEST MODE menu from the HDS.
Are any DTCs indicated?
YES -Go to B-CAN System Diagnosis Test Mode A (see TROUBLESHOOTING - B-CAN SYSTEM DIAGNOSIS TEST MODE A ).
NO -Go to step 3.
- Turn ON the switch that controls the malfunctioning component.
- Select DATA LIST from the TEST MODE menu, and check output signal for the malfunctioning component.
Is there an output signal?
YES -Go to step 5.
NO -Go to step 9.
- Test the relay and ground that controls the device that does not work, if applicable. If the relay and ground test OK, then check for an open or a short in the circuit for the malfunctioning component.
Is the relay and the circuit OK?
YES -Go to step 6.
NO -Replace the relay, or repair the circuit.
- Do the function test for the malfunctioning component.
Does the output device pass the function test?
YES -Go to step 7.
NO -Replace the component.
- With the malfunctioning output device connected, connect a voltmeter between the malfunctioning output device input and the ground wire that the control unit uses to control the output device circuit.
- Select MISC. TEST from the TEST MODE menu, and do the forced operation test of the malfunctioning component.
Is there a change in voltage (12 V to 0 V or 0 V to 12 V)?
YES -Inspect the ground for the component. If OK, replace the component.
NO -Replace the control unit that controls the malfunctioning components
- Select DATA LIST from the TEST MODE menu, and make sure the switch signal input for the malfunctioning system indicates a change when operated.
Does the switch input indicate ON when the switch Is ON?
YES -Replace the control unit that controls the malfunctioning component.
NO -Go to step 10.
- Test the switch and its ground (if applicable), then check for an open or a short in the wire between the switch and the control unit that monitors it.
Is the switch and the wire harness OK?
YES -Replace the control unit that monitors the switch.
NO -Replace the switch, or repair/replace the wire harness.
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.