The GMC Envoy, manufactured from 1998 until 2009, has an on-board diagnostics feature (called OBD II) that allows a car owner or mechanic to diagnose engine problems by reading diagnostic trouble codes (DTCs) that are generated by sensors in the powertrain. If a sensor detects a problem, it will illuminate the Envoy's check-engine light on the instrument panel. Then a car owner or mechanic can read the trouble codes are using a handheld scan tool to diagnose and fix the engine problem. When the problem is fixed, you'll want to know how to turn off the check-engine light.
Read the instruction manual for the OBD II DTC reader and eraser. There are many varieties that feature different options and have different methods for reading and erasing codes. While very easy to operate, the instruction manual will direct you how to properly use the reader.
Open the GMC Envoy's driver-side door and look under the dashboard to locate the OBD II connector.
Place the plug of the reader into the connector. Because of its shape, you can only plug it in one way.
Place the key in the ignition and turn the key two clicks forward to the accessory power position. This will illuminate the lights on the instrument panel without starting the engine of the Envoy.
Turn the power button on the reader (if equipped; most will turn on when the ignition key is turned to the "on" position).
Follow the steps from the instruction manual to read and erase the DTC(s). It is advisable to write the codes on a piece of paper.
Wait for the reader to tell you from the onscreen menu that the diagnostic trouble code has been erased, then unplug it from the connector.
Start the engine of the Envoy and look at the instrument panel to ensure the check-engine light is out.
