Have you recently replaced your Ford’s Powertrain Control Module (PCM) or even just disconnected/replaced the battery, only to find your vehicle failing its emissions test due to an “emission control system not ready” OBDII status? This is a common frustration for car owners and technicians alike. Understanding why this happens and how to resolve it is crucial to get your vehicle back in optimal running condition and pass those essential emissions checks. This guide will walk you through the reasons behind this “not ready” status and provide a step-by-step approach to reset your emission monitors and ensure your OBDII system is ready for inspection.
Understanding OBDII Readiness Monitors
Modern vehicles, including your Ford, utilize an On-Board Diagnostic system (OBDII) to monitor the performance of various emission control components. These systems include monitors that continuously check components like the catalytic converter, oxygen sensors, evaporative system, and more. For your vehicle to pass an emissions test, these monitors need to complete their self-tests and report a “ready” status. When these monitors are “not ready,” it signifies that the system hasn’t yet confirmed the proper functioning of these crucial emission components.
Why “Not Ready” After PCM or Battery Change?
The PCM is the brain of your vehicle’s engine management system. When you replace the PCM or disconnect the battery, you are essentially resetting this brain. This reset clears the learned adaptations and also resets the OBDII readiness monitors to a “not ready” state. This is because the PCM needs to re-run its diagnostic routines to confirm all emission systems are operating correctly after the change. Think of it as the car needing to re-learn and re-verify everything is in order after a significant system change or power interruption.
Specifically, disconnecting the battery or replacing the PCM erases the “readiness flags” stored in the PCM’s memory. These flags indicate whether each emission monitor has completed its diagnostic cycle. Until the vehicle completes a specific set of driving conditions, known as a “drive cycle,” these monitors will remain in the “not ready” state.
The Emission System Relearn Process: The Drive Cycle
To reset these monitors to “ready,” you need to perform a drive cycle. A drive cycle is a pre-defined sequence of driving conditions that allows the PCM to run all the necessary self-tests for the emission monitors. The exact drive cycle can vary slightly depending on the vehicle make, model, and year. However, the general principles remain consistent.
For many Ford vehicles, including models similar to the 2013 Edge SEL referenced in the original document, a general drive cycle procedure involves a combination of idling, steady speed driving, and acceleration/deceleration. This allows the PCM to assess various operating conditions and complete its diagnostic checks.
Here’s a generalized drive cycle procedure, incorporating elements from the original Ford document, to help reset your emission monitors:
-
Initial Conditions: Ensure your vehicle is at a complete stop and the parking brake is engaged. Shift the gear selector to “P” (Park). Turn off all unnecessary accessories like headlights, radio, and climate control to minimize electrical load.
-
Engine Start and Warm-up: Start the engine and allow it to run until it reaches its normal operating temperature. This ensures the engine and catalytic converter are warm enough for proper emission system testing.
-
Idle Phase: Let the engine idle for at least one minute after it has reached normal operating temperature. This allows the PCM to test idle-related emission components.
-
Idle with A/C On: Turn the air conditioning (A/C) system on and let the engine idle for another minute. This tests the emission system under a slightly different engine load condition.
-
Driving Phase: This is the most crucial part. Drive the vehicle under various conditions to allow all monitors to run:
- Moderate Acceleration and Deceleration: Perform several gentle accelerations and decelerations. Avoid hard braking or sudden acceleration.
- Maintain Steady Speed: Drive at a steady speed, such as 45-55 mph (70-90 km/h), for several minutes on a relatively flat and straight road if possible.
- Varying Speeds (if safe and applicable): If safe and conditions permit, you can also incorporate some driving at slightly higher and lower speeds within legal limits.
Important Considerations for Drive Cycles:
- Safety First: Always perform drive cycles in a safe location where you can legally and safely perform the required maneuvers. Avoid heavy traffic areas.
- Patience is Key: The drive cycle may need to be repeated and can sometimes require driving for 10 miles (16 km) or more, as mentioned in the original document, to complete the relearning process and set all monitors to “ready.”
- No Diagnostic Trouble Codes (DTCs): Ensure there are no active diagnostic trouble codes (check engine light is off) before starting the drive cycle. Existing DTCs can prevent monitors from setting to “ready.” Address any DTCs first.
Ford Specific Relearn (Based on Original Procedure for 2013 Edge SEL):
The original text, while focused on battery disconnection, provides a good starting point for a Ford relearn procedure applicable to emission monitors as well:
- With the vehicle at a complete stop, set the parking brake.
- Put the gearshift in P (Park), turn off all accessories and start the engine.
- Run the engine until it reaches normal operating temperature.
- Allow the engine to idle for at least one minute.
- Turn the A/C on and allow the engine to idle for at least one minute.
- Drive the vehicle to complete the relearning process. The vehicle may need to be driven 10 miles (16 km) or more to relearn the idle and fuel trim strategy.
While this procedure is presented in the context of idle and fuel trim relearn after battery disconnection, the principles of warm-up, idling, and driving are directly relevant to completing a drive cycle for emission monitor readiness.
Troubleshooting Persistent “Not Ready” Issues
If you have performed a drive cycle and your OBDII emission control system result is still “not ready,” consider these troubleshooting steps:
- Repeat the Drive Cycle: Sometimes, a single drive cycle is not sufficient. Repeat the drive cycle procedure a few more times, ensuring you are following the steps accurately.
- Check for Pending Codes: Use an OBDII scanner to check for any pending diagnostic trouble codes. Even if the check engine light is not illuminated, pending codes can prevent monitors from setting to “ready.”
- Component Issues: In rare cases, a persistent “not ready” status, even after multiple drive cycles, could indicate an underlying issue with an emission control component itself. A faulty oxygen sensor, catalytic converter, or evaporative system component might prevent the corresponding monitor from completing its test. In such cases, professional diagnosis is recommended.
- PCM Programming: If you have replaced the PCM, ensure it was correctly programmed and configured for your specific vehicle. Incorrect PCM programming can lead to various issues, including emission monitor problems.
Conclusion
Seeing an “emission control system result not ready” message after a PCM or battery change can be concerning, but it’s often a normal part of the vehicle’s relearning process. By understanding the role of OBDII readiness monitors and performing a proper drive cycle, you can typically reset these monitors to “ready” and ensure your vehicle is prepared for emissions testing. Remember to be patient, drive safely, and if issues persist, don’t hesitate to consult a qualified automotive technician for further diagnosis and repair.
