The OBDII (On-Board Diagnostics) port is crucial for diagnosing car problems. If your GMC Envoy’s OBDII port isn’t working, this guide will help you troubleshoot the issue, specifically focusing on a potential problem with Fuse 13. A common symptom is also a malfunctioning cigarette lighter port, often registering only 6 VDC instead of the expected 12 VDC.
Checking Fuse 13 in the Underhood Fuse Box
The first step in troubleshooting a powerless OBDII port on a GMC Envoy is to check Fuse 13 located in the underhood fuse box. Even if the fuse appears visually intact, it could be faulty. Replace Fuse 13 with a known good 20 Amp fuse. Sometimes, fuses can be defective due to internal damage or oxidized terminals.
Verifying Power After Fuse Replacement
After replacing Fuse 13, check both the OBDII port and the cigarette lighter port. The OBDII port should now be active, and the cigarette lighter port should register 12 VDC. Both are directly connected to the load side of Fuse 13. Refer to the wiring diagram for the OBDII and cigarette lighter circuit if needed. This diagram usually highlights a simple circuit path from the fuse box to both components.
Testing for Voltage at Fuse 13
If the problem persists, use a multimeter (digital multimeter preferred) to check for voltage at Fuse 13. With the multimeter set to DC volts, ground the black lead. With Fuse 13 in place, touch the red probe to each exposed terminal of the fuse. You should read 12 VDC on both sides. This confirms power is reaching the fuse.
Checking for Continuity Between Fuse 13 and OBDII Port
If you don’t detect 12 VDC on both sides of Fuse 13, switch your multimeter to ohms. Connect one lead to the load side (0 voltage side) of Fuse 13’s contacts in the fuse box and the other lead to pin 16 of the OBDII port. A reading of zero ohms indicates a good connection. A higher reading suggests a break in the wiring between the fuse box and the OBDII port, requiring further inspection and repair of the wiring. This often involves tracing the wire from the OBDII port back to the fuse block.
Conclusion
A powerless OBDII port on a GMC Envoy is often caused by a faulty Fuse 13. This guide provides a step-by-step approach to diagnose and potentially fix the issue. By checking the fuse, verifying power, and testing for continuity, you can pinpoint the problem and get your OBDII port working again, allowing you to diagnose any underlying vehicle issues using a code reader or scanner. Remember to consult your vehicle’s repair manual for specific instructions and safety precautions.
