If you own a 2003 Honda Accord EX and need to pass an emissions test, understanding the OBD2 drive cycle is crucial. Your vehicle’s On-Board Diagnostic system (OBD2) includes “readiness monitors” that assess the performance of your car’s emission control systems. These monitors need to be in a “ready” state to confirm that these systems are functioning correctly. If they aren’t, your Accord might fail the emissions test, even if there are no obvious problems.
This guide will explain what OBD2 readiness monitors are, why they matter for your 2003 Honda Accord EX, and how to perform a drive cycle to set these monitors to a “complete” or “ready” status.
Understanding OBD2 Readiness Monitors
Readiness monitors are self-tests performed by your Honda Accord’s engine computer (PCM or ECM) to check various emission control systems. These systems include:
- Catalytic Converter: Reduces harmful pollutants in exhaust gases.
- Evaporative Emission (EVAP) System: Prevents fuel vapors from escaping into the atmosphere.
- Oxygen (O2) Sensors & Heater: Monitors and adjusts the air-fuel mixture for optimal combustion and catalytic converter efficiency.
- Exhaust Gas Recirculation (EGR) System: Reduces NOx emissions by recirculating a portion of exhaust gas back into the engine intake.
- Misfire Monitor: Detects engine misfires, which can increase emissions and damage the catalytic converter.
- Fuel System Monitor: Checks for fuel leaks and proper fuel delivery.
- Comprehensive Components Monitor: A general check of various engine management components.
When your car’s battery is disconnected, Diagnostic Trouble Codes (DTCs) are cleared, or the PCM/ECM is reset, these readiness monitors are reset to an “not ready” or “incomplete” state. They need to run and complete their self-tests before they show as “ready.”
Checking Readiness Monitor Status on Your 2003 Honda Accord EX
You can check the status of your readiness monitors without specialized tools, although a scan tool provides more detailed information.
Using the Malfunction Indicator Lamp (MIL) / Check Engine Light:
- Turn the ignition switch to the ON (II) position, but do not start the engine.
- Observe the Malfunction Indicator Lamp (MIL), also known as the Check Engine Light. It will illuminate for approximately 15-20 seconds.
- Readiness Codes Complete: If the MIL turns off after 15-20 seconds and stays off, all readiness codes are likely set to “complete.”
- Readiness Codes Incomplete: If the MIL flashes five times after 15-20 seconds, it indicates that one or more readiness codes are “not set to complete.”
Using a Scan Tool (Recommended for Detailed Information):
For a more precise check, especially to identify which monitors are incomplete, use an OBD2 scan tool. A scan tool allows you to:
- View the status of each individual readiness monitor.
- Check for pending or stored Diagnostic Trouble Codes (DTCs) that might be preventing readiness monitors from setting.
Performing an OBD2 Drive Cycle for a 2003 Honda Accord EX
A drive cycle is a specific sequence of driving conditions designed to allow the OBD2 system to run all the necessary self-tests and set the readiness monitors to “complete.” The following are drive cycle procedures for specific monitors on your 2003 Honda Accord EX. Always follow local traffic laws and safety precautions when performing a drive cycle.
General Notes for All Drive Cycles:
- Honda Diagnostic System (HDS) is mentioned in the original text, but for most DIYers and general purposes, an OBD2 scan tool for monitoring readiness status is sufficient.
- Do not turn off the ignition during any procedure unless specifically instructed.
- Ensure your 2003 Honda Accord EX is in good working order with no major engine or emission system faults.
- Low ambient temperatures or heavy stop-and-go traffic may extend the time needed to complete a drive cycle.
- Readiness codes will not set to complete if there are underlying issues or fault codes present in the related system.
1. Catalytic Converter Monitor Drive Cycle
The catalytic converter monitor checks the efficiency of your Accord’s catalytic converter.
Enable Criteria:
- Engine Coolant Temperature (ECT) at or above 158°F (70°C).
- Intake Air Temperature (IAT) at or above -13°F (-25°C).
- Vehicle Speed Sensor (VSS) reading above 3 mph (5 km/h).
Procedure:
- Connect a scan tool to your vehicle’s Data Link Connector (DLC) and access the “READINESS CODEs” screen for the Catalyst monitor.
- Start the engine.
- Drive Cycle: Drive your 2003 Honda Accord EX under stop-and-go conditions with short periods of steady cruising for approximately 5 miles (8 km).
- Check Readiness: After driving, check the readiness code status for the Catalytic Converter monitor using your scan tool. It should indicate “complete.”
- If Incomplete: If the readiness code is still not set, check for Temporary DTCs with your scan tool. If no DTCs are present, repeat the procedure, ensuring all enable criteria are met.
2. Evaporative Emission (EVAP) Control System Monitor Drive Cycle
The EVAP system monitor checks for leaks and proper functioning of the evaporative emissions control system.
Enable Criteria:
- Battery voltage above 10.5 V.
- Engine at idle.
- Engine Coolant Temperature (ECT) between 176°F (80°C) and 212°F (100°C).
- Manifold Absolute Pressure (MAP) sensor reading below 46.6 kPa (14 in.Hg, 350 mmHg).
- Vehicle speed 0 mph (0 km/h).
- Intake Air Temperature (IAT) sensor between 32°F (0°C) and 212°F (100°C).
Procedure:
- Connect a scan tool to your vehicle’s DLC.
- Start the engine.
- Using your scan tool, navigate to the “INSPECTION MENU” and select “EVAP TEST.” Then, select “FUNCTION TEST” within the EVAP TEST menu.
- EVAP System Test: Follow the scan tool’s prompts to perform the EVAP system function test.
- Check Readiness: If the function tests are normal, the EVAP readiness monitor should be complete. Check the readiness status using your scan tool.
- If Incomplete: If the readiness code is still incomplete, check for temporary DTCs. If no DTCs are present, repeat the procedure, ensuring all enable criteria are met.
3. Air Fuel Ratio (A/F) Sensor Monitor Drive Cycle
The Air Fuel Ratio (A/F) sensor monitor checks the performance of the primary oxygen sensor, which is crucial for fuel efficiency and emissions control.
Enable Criteria:
- Engine Coolant Temperature (ECT) at or above 158°F (70°C).
Procedure:
- Start the engine.
- Drive Cycle: Drive your 2003 Honda Accord EX under stop-and-go conditions with short periods of steady cruise for approximately 3.5 miles (5.6 km).
- Deceleration Phase: During the drive, perform deceleration (coast down) with the throttle fully closed for at least 5 seconds.
- Check Readiness: After driving, check the readiness code status for the Air Fuel Ratio (A/F) Sensor monitor using your scan tool. It should indicate “complete.”
- If Incomplete: If the readiness code is still not set, check for Temporary DTCs. If no DTCs are present, verify that the Engine Coolant Temperature (ECT) is above 158°F (70°C) using the scan tool’s data list. If ECT is too low, allow the engine to warm up further and repeat the procedure.
4. Air Fuel Ratio (A/F) Sensor Heater Monitor Readiness Code
This monitor specifically checks the heater element within the primary oxygen sensor, which ensures the sensor reaches operating temperature quickly.
Procedure:
- Start the engine.
- Idle: Let the engine idle for 1 minute.
- Check Readiness: After idling, check the readiness code status for the Air Fuel Ratio (A/F) Sensor Heater monitor using your scan tool. It should indicate “complete.”
- If Incomplete: If the readiness code is still not set, check for temporary DTCs. If no DTCs are present, repeat the procedure.
5. EGR Monitor Drive Cycle
The EGR monitor verifies the proper function of the Exhaust Gas Recirculation system.
Enable Criteria:
- Engine Coolant Temperature (ECT) at or above 176°F (80°C).
Procedure:
- Connect a scan tool to your vehicle’s DLC.
- Start the engine.
- Cruise Phase: Drive at a steady speed between 50-62 mph (80-100 km/h) or above for more than 10 seconds with the automatic transmission in “D” or manual transmission in 4th gear.
- Deceleration Phase: With the transmission still in “D” or 4th gear, decelerate from 62 mph (100 km/h) or above by completely releasing the throttle for at least 5 seconds. Do not stop the engine during deceleration.
- Check Readiness: Check the OBD status screen for DTC P0401 (EGR insufficient flow) using your scan tool. If the test “passed,” the EGR readiness monitor is complete.
- If Not Passed: If the test did not pass, repeat steps 3 and 4.
Monitors Always Ready
The following monitors are continuously monitored and should always be in a “ready” state when the engine is running and conditions are met:
- Misfire Monitor
- Fuel System Monitor
- Comprehensive Component Monitor
Conclusion
Successfully completing the OBD2 drive cycle for your 2003 Honda Accord EX is essential for passing emissions tests and ensuring your vehicle is running efficiently and cleanly. By following these procedures and using a scan tool to monitor readiness status, you can confidently prepare your Honda Accord for its next emissions inspection. Remember to address any underlying mechanical issues if readiness monitors are consistently failing to set, as they often indicate a problem that needs attention.
