The OBD2 port on your 2004 GMC Envoy isn’t working? A common culprit is a faulty fuse. This guide will walk you through diagnosing and fixing the issue, focusing specifically on Fuse 13, which powers the OBD2 port and cigarette lighter.
A malfunctioning OBD2 port can prevent you from reading diagnostic trouble codes, hindering your ability to troubleshoot vehicle problems. If your cigarette lighter also isn’t working, it further points towards a potential fuse issue. Often, a visual inspection isn’t enough to confirm a blown fuse, as they can fail internally.
The first step is to replace Fuse 13, located in the underhood fuse box. This is a 20-amp fuse, so ensure you use the correct replacement. Even if the old fuse looks intact, internal damage or oxidized terminals can disrupt the electrical connection.
After replacing Fuse 13, check both the OBD2 port and the cigarette lighter. The OBD2 port should now be active, and the cigarette lighter should register 12 volts DC.
If the problem persists, use a multimeter to verify power at Fuse 13. With the multimeter set to DC volts, ground the black lead and touch the red lead to each exposed terminal of the fuse. You should read 12 volts on both sides. This confirms power is reaching the fuse.
If you don’t have 12 volts on both sides of the fuse, there might be an issue in the wiring leading up to the fuse box. If you have 12 volts at the fuse but not at the OBD2 port, the problem lies between the fuse and the port.
To test the circuit continuity, switch your multimeter to ohms. Connect one lead to the load side (0 voltage side) of Fuse 13 and the other lead to pin 16 of the OBD2 port. A reading of zero ohms indicates a good connection. A higher reading suggests a break in the wiring.
If the continuity test reveals a problem, you’ll need to trace the wire from Fuse 13 to the OBD2 port, looking for damage or disconnections. Refer to a wiring diagram for your 2004 GMC Envoy to identify the correct wire path. The wiring for the OBD2 port and cigarette lighter is relatively simple, often running directly from the fuse box.
By systematically checking the fuse, power supply, and wiring continuity, you can pinpoint the cause of the malfunctioning OBD2 port. Once the electrical issue is resolved, you can use your code reader to diagnose any underlying vehicle problems. Replacing Fuse 13 is often the solution, but these further steps will help you troubleshoot more complex electrical issues affecting your OBD2 port.
