The EVAP (Evaporative Emission Control System) monitor in GM vehicles, including the Buick Lacrosse, is notoriously complex. Getting it to complete its cycle and switch from “NOT READY” to “READY” for emission testing can be a challenge. This process often requires multiple cold start drive cycles and sometimes even a full tank of gas due to the stringent parameters it needs to meet. Understanding the correct procedure is crucial, especially if you’ve been dealing with a check engine light or trouble codes related to your Buick Lacrosse’s emissions system. After performing the necessary steps, a DTC scan tool becomes an indispensable tool to verify the system’s status and clear any lingering diagnostic trouble codes (DTCs).
Understanding the GM EVAP Monitor Procedure for Your Buick Lacrosse
The Inspection/Maintenance (I/M) complete system set procedure is designed to fulfill all the necessary criteria for running I/M readiness diagnostics. When all monitored diagnostic tests are successfully completed, the I/M System Status indicators will display “YES”. This procedure is essential if any of these indicators are showing “NO”, often after repairs or battery disconnection. For Buick Lacrosse owners, following this procedure diligently can save time and ensure your vehicle passes emission tests.
To check if your Buick Lacrosse is ready for the procedure, use a scan tool to look at the I/M monitor-enabled parameters in the I/M Data List. Before you begin, ensure your vehicle meets the following “cold start” conditions:
- Voltage: Battery voltage between 11-18 volts.
- Barometric Pressure (BARO): Above 75 kPa.
- Engine Coolant Temperature (ECT): Startup ECT between 4-30°C (39-86°F).
- Intake Air Temperature (IAT): Startup IAT between 4-30°C (39-86°F).
- IAT and ECT Difference: Less than or equal to 6°C (10.8°F).
- Ambient Air Temperature: Between 4-30°C (39-86°F).
- Fuel Level: Between 15-85 percent.
- Fuel Alcohol Content: Specific limits apply based on engine type (check your vehicle’s specifications).
Important Pre-Procedure Steps: Before starting the procedure, turn OFF the ignition for about 5 minutes to allow sensors to cool down. Once the engine is started for the procedure, do NOT turn it off until completion.
Step-by-Step I/M System Set Procedure for Buick Lacrosse
Follow these steps precisely to complete the I/M system set procedure on your Buick Lacrosse.
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Cold Start Conditions: Ensure all the cold start conditions mentioned above are met. If the EVAP I/M System Status indicator shows “NO”, and an EVAP service bay test isn’t available, understand that it might take up to 6 drive cycles (and up to 17 hours between each) for the EVAP monitor to reset. If the O2S Heater System Status indicator is “NO”, ensure the ignition has been off for at least 10 hours.
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Parking Brake and Gear: Engage the parking brake and ensure the vehicle is in Park (automatic) or Neutral (manual).
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Turn Off Accessories: Switch off all accessories, including HVAC, lights, and any aftermarket electrical equipment.
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Initial Idle: Start the engine and let it idle for at least 2 minutes until the engine temperature reaches 65°C (149°F).
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Elevated Idle: Run the engine for 6.5 minutes under these conditions:
- MAF parameter between 4-30 g/s
- Engine speed steady between 1000-3000 RPM
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Return to Idle: Let the engine idle for 1 minute.
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Drive Load: Apply the brake pedal, shift to Drive (automatic) or engage the clutch (manual), and operate for 2 minutes under these conditions:
- Accelerator pedal angle more than 2 percent.
- MAF signal between 15-30 g/s
- RPM steady between 1200-2000 RPM
Important: Do NOT touch the accelerator during idle periods. Any change in throttle position or engine speed can invalidate the test.
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Idle Again: Release the accelerator, shift to Park (automatic) or Neutral (manual), and idle for 2 minutes.
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Throttle Bursts: Quickly depress the accelerator until the TP Sensor Angle is more than 8 percent, then return to idle. Repeat this 3 times.
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Extended Idle: Allow the engine to idle for at least 2 minutes.
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Low Speed Drive: Release the parking brake and drive at 24 km/h (15 mph) or slower for 2 minutes.
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Highway Speed Drive: Continue driving for at least 5.5 miles between 45-112 km/h (28-70 mph), reaching at least 80 km/h (50 mph).
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Deceleration: Release the accelerator for at least 2 seconds to allow for deceleration fuel cut-off.
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Moderate Acceleration: Depress the accelerator pedal to increase TP Sensor angle by 3-20 percent and maintain a safe speed for 1 minute.
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Stop and Idle in Drive: Safely stop the vehicle, keeping it in Drive (automatic) or Neutral with clutch engaged (manual) and parking brake applied, and idle for 2 minutes.
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Final Idle in Park/Neutral: Shift to Park (automatic) and apply parking brake, or Neutral (manual).
Important: Do NOT disturb the vehicle or turn ON the ignition until instructed. Any disturbance can invalidate the test.
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Cool Down Period: Turn OFF the ignition and exit the vehicle. Do not disturb it for 45 minutes.
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Scan Tool Verification: After 45 minutes, use your DTC scan tool to observe the I/M System Status. All indicators should now display “YES”.
- If the EVAP I/M System Status is still “NO”, turn OFF the ignition for 17 hours, ensure cold start conditions are met, and repeat steps 12-18 up to six more times. If it remains “NO”, consult the I/M System DTC Table to identify any DTCs and follow the specific conditions for running those DTCs.
- If any other I/M System Status indicators are “NO”, refer to the I/M System DTC Table to find associated DTCs and address them accordingly.
Using a DTC Scan Tool to Clear Codes on Your Buick Lacrosse
After successfully completing the EVAP monitor procedure, you might still have stored DTCs related to the EVAP system or other emissions components. This is where a DTC scan tool becomes essential. A scan tool allows you to:
- Verify Monitor Status: Confirm if the EVAP monitor and other I/M monitors are indeed set to “READY”.
- Read Diagnostic Trouble Codes (DTCs): Identify any current or pending DTCs in the vehicle’s computer system.
- Clear DTCs: Once you’ve addressed the underlying issues and the monitors are ready, you can use the scan tool to clear the DTCs, turning off the check engine light.
For a Buick Lacrosse, a standard OBD2 scan tool will be compatible. Connect the scan tool to your vehicle’s OBD2 port (usually located under the dashboard on the driver’s side). Follow the scan tool’s instructions to read and clear codes.
Choosing the Right DTC Scan Tool: While basic scan tools can read and clear codes, more advanced scan tools offer features like live data streaming, graphing, and enhanced diagnostics, which can be beneficial for in-depth troubleshooting. For simply clearing codes after the EVAP monitor procedure on your Buick Lacrosse, a basic, reliable DTC scan tool will suffice.
Conclusion
Successfully completing the GM EVAP monitor procedure for your Buick Lacrosse is a detailed process. By following these steps carefully and utilizing a DTC scan tool, you can ensure your vehicle’s emission system is properly monitored, and clear any related trouble codes. This not only helps in passing emission tests but also contributes to the overall health and performance of your Buick Lacrosse. Remember to always consult your vehicle’s service manual for specific details and recommendations related to your model year.
