If your Mazda 3’s OBDII system displays an “INC” (Incomplete) status for the catalyst monitor, it means the vehicle’s onboard diagnostic system hasn’t completed its self-test for the catalytic converter. This article outlines the specific drive cycle procedure to help complete this test and potentially clear the “INC” status. An incomplete test can prevent you from passing emissions testing.
Catalyst Monitor Drive Cycle: Step-by-Step Guide
Before starting, ensure your Mazda 3 meets these pre-conditions:
- MIL (Malfunction Indicator Lamp) is off.
- No emission-related Diagnostic Trouble Codes (DTCs) are present.
- Engine Coolant Temperature (ECT) sensor signal is above 167°F.
- Intake Air Temperature (IAT) sensor signal is above 14°F.
- Idle speed and ignition timing are set to manufacturer specifications.
Procedure:
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Connect an OBDII scan tool: Plug the scan tool into the Data Link Connector (DLC) under the dashboard. Clear any stored DTCs and reset the Onboard Diagnostic Monitors. Access the Readiness Code for the Catalyst Monitor.
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Warm up the engine: Start the engine and let it idle until the ECT reading on the scan tool reaches at least 167°F.
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No-load acceleration: Shift to Park (P) or Neutral (N) for automatic transmissions. Accelerate the engine to 2,500-3,500 RPM and hold for 15 seconds. Let the engine return to idle and wait for 60 seconds after the cooling fan stops running. Monitor the RPM on the scan tool to ensure accuracy during this step.
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Steady and varying speed driving: For automatic transmissions, shift to Drive (D). For manual transmissions, use 5th gear. Accelerate to above 40 mph and maintain this speed for 1 minute. Then, decelerate to between 45-55 mph and hold for 3 minutes. Return to idle. Finally, accelerate to 55 mph and alternate between 50-55 mph for 10 seconds at each speed (10 seconds at 55mph, 5 seconds coasting down to 50 mph, repeat). Bring the vehicle to a complete stop without turning off the ignition.
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Check the readiness code: Using the scan tool, check the Catalyst Monitor’s readiness code. It should now show “YES” or “Complete.” If it does, you may need to perform additional driving cycles for other monitors. If the status remains “INC” or “Not Complete,” check for pending codes in the generic OBDII section of the scan tool. If no pending codes exist, repeat the drive cycle from Step 3.
Important Considerations
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Accuracy is key: Adhere to the specified RPM and speed ranges as closely as possible. Using an assistant to monitor the scan tool can be helpful.
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Don’t interrupt the process: Avoid turning off the ignition during the drive cycle. Interruptions will require restarting the entire procedure.
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Persistent “INC” status: If the catalyst monitor remains incomplete after multiple attempts, there may be an underlying issue with the catalytic converter or other emission-related components. Consult a qualified mechanic for further diagnosis and repair.
This drive cycle is specifically designed to enable the catalyst monitor self-test. Following these steps accurately will provide the best chance of clearing the “INC” status on your Mazda 3’s OBDII system.
