The OBDII port on your 2004 Chevy Trailblazer is crucial for diagnosing engine problems. If it’s not working, and your cigarette lighter only outputs 6 volts, a faulty fuse is often the culprit. This guide pinpoints the likely cause and provides troubleshooting steps.
Fuse 13: The Prime Suspect
The primary suspect in this scenario is Fuse 13, located in the underhood fuse box. Even if it looks intact, it might be defective. Replace it with a known good 20-amp fuse. This fuse powers both the OBDII port and the cigarette lighter.
Verification After Fuse Replacement
After replacing Fuse 13, check if the OBDII port is now active. You can test this by plugging in a code reader or checking for 12 volts at the cigarette lighter.
Understanding the Circuitry
The wiring diagram reveals a simple circuit. Power flows from the load side of Fuse 13 directly to pin 16 of the OBDII port and the center terminal (Pin A) of the cigarette lighter.
Further Diagnostics with a Multimeter
If the problem persists, use a multimeter for further diagnostics:
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Voltage Test: With the fuse in place and the multimeter set to DC volts, ground the black lead. Touch the red probe to each exposed terminal of Fuse 13. You should measure 12 volts on both sides.
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Resistance Test: If you don’t get 12 volts, switch the multimeter to ohms. Connect one lead to the load side of Fuse 13 and the other to pin 16 of the OBDII port. A reading of zero ohms indicates a good connection. A higher reading suggests a wiring issue between the fuse box and the OBDII port. You may need to trace the wire for breaks or damage.
Next Steps After Troubleshooting
Once you’ve restored power to the OBDII port, connect a code reader to retrieve any stored diagnostic trouble codes (DTCs). These codes provide valuable insights into the underlying issues affecting your vehicle.
By following these steps, you can effectively troubleshoot and resolve power issues related to the OBDII port and cigarette lighter on your 2004 Chevy Trailblazer. Remember to always consult your vehicle’s owner’s manual for specific fuse box diagrams and further information.
