The OBDII (On-Board Diagnostics II) system in your 2012 GMC Acadia monitors various vehicle components for malfunctions. When a problem is detected, a diagnostic trouble code (DTC) is stored in the system’s memory. To accurately diagnose issues and ensure proper repairs, sometimes a specific drive cycle must be performed to allow the system to complete its self-tests. This article outlines the proper GM OBDII drive cycle for a 2012 GMC Acadia.
Understanding the GM OBDII Drive Cycle
A specific driving sequence, known as a drive cycle, enables your Acadia’s OBDII system to run checks on components like the catalytic converter, oxygen sensors, evaporative emissions system, and EGR system. Completing this cycle helps ensure accurate diagnostic results.
Cold Start: The First Step
Begin with a cold start. This requires the engine coolant temperature to be below 122°F (50°C) and within 11°F (6°C) of the outside air temperature. Avoid leaving the key in the ignition prior to starting to allow the heated oxygen sensor diagnostic to run correctly. Start the engine.
Idle Phase with Loads
Let the engine idle for two and a half minutes with the air conditioner and rear defroster turned on. Applying additional electrical loads can aid in a more thorough test. This phase tests components like the oxygen sensor heater, passive air intake, purge system, and fuel trim.
Acceleration and Steady Speed
Turn off the AC and other loads. Accelerate at half throttle until reaching 55 mph (88 km/h). Maintain this speed for 3 minutes. This tests the misfire, fuel trim, purge flow, oxygen sensor response, EGR system, and air intrusion systems.
Deceleration Phase
Decelerate to 20 mph (32 km/h) without braking, shifting, or using the clutch. Allow the vehicle to coast. This tests the EGR, purge, and fuel trim systems.
Second Acceleration and Extended Steady Speed
Accelerate again to 55-60 mph (88-96 km/h) using 3/4 throttle and maintain this speed for 5 minutes. This extended period enables the catalytic converter monitor diagnostics to run completely.
Final Deceleration
Finally, decelerate to 20 mph (32 km/h) without braking or shifting, allowing the car to coast. This final step completes the GM OBDII drive cycle for your 2012 GMC Acadia. Remember that a complete drive cycle might need to be repeated several times, especially if the catalytic converter is marginal or the battery has been disconnected recently.
