If scan tester displays UNABLE TO CONNECT TO VEHICLE when scan tester is connected, try scan tester on another vehicle. If scan tester operates on another vehicle, go to next step. If scan tester does not operate on another vehicle, problem is probably with scan tester.
Check DLC3 for loose or damaged terminals. Ensure DLC3 terminals are in correct position in connector. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If connector and terminals are okay, go to next step.
Check voltage and resistance between ground and specified terminal on DLC3. See DLC3 VOLTAGE & RESISTANCE SPECIFICATIONS table. See Fig 1. If voltage and resistance readings are not as specified, check wiring circuit. See appropriate wiring diagram in WIRING DIAGRAMS article.

NOTE: Terminal No. 2 on DLC3 provides the pulse generation during the information transmission from the Engine Control Module (ECM).

DLC3 VOLTAGE & RESISTANCE SPECIFICATIONS

Fig 1: Identifying DLC3 Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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.

Safety Warning

DLC3 Inspection