A non-functional OBD-II port can be frustrating. This guide focuses on troubleshooting the common issue of a missing 12V power supply at the OBD-II port, often related to the fuse block and specifically fuse 13. We’ll walk through a diagnostic process to identify the problem and get your port working again.
Identifying the Problem: No Power at the OBD2 Port
If your OBD-II port isn’t working and your cigarette lighter only shows 6V, the first step is to check fuse 13 in the underhood fuse box. Even if the fuse looks intact, it could be blown or defective. A faulty fuse can interrupt the 12V power supply to both the OBD-II port and the cigarette lighter. Replacing fuse 13 with a known good 20 Amp fuse is the easiest initial step.
The wiring diagram for the OBD-II and cigarette lighter illustrates a simple circuit. Power flows from the load side of fuse 13 directly to pin 16 of the OBD-II port and the center terminal (Pin A) of the cigarette lighter.
Testing for Voltage and Continuity
After replacing fuse 13, check the OBD-II port and cigarette lighter for 12V. If the issue persists, use a multimeter to test for voltage and continuity.
Voltage Test:
- Set your multimeter to DC volts.
- Ground the negative (black) lead.
- With fuse 13 installed, touch each exposed terminal of the fuse with the positive (red) probe. You should read 12V on both sides.
Continuity Test:
- If you don’t find 12V on both sides of fuse 13, switch your multimeter to ohms.
- Connect one lead to the 0 voltage side (load side) of fuse 13’s contacts.
- Connect the other lead to pin 16 of the OBD-II port. A reading near zero ohms indicates a good connection.
Tracing the Wiring
If the continuity test reveals a problem, you’ll need to trace the wiring between the fuse block and the OBD-II port to pinpoint the fault. This might involve inspecting the wiring harness for damage, breaks, or loose connections.
Conclusion
By systematically checking the fuse, voltage, and continuity, you can diagnose and fix the problem of a missing 12V power supply to your OBD-II port. In many cases, a simple fuse replacement will solve the issue. However, if the problem persists, further investigation of the wiring between the fuse block and the OBD-II port is necessary. Once the 12V connection is restored, you can use your code reader or scanner to diagnose any underlying vehicle issues.
