Navigating the complexities of vehicle emissions systems can be frustrating, especially when it comes to OBDII readiness monitors. For BMW owners, a common concern arises when these monitors, specifically related to the EVAP system or others, fail to show as “ready” for smog checks or diagnostic purposes. This article delves into the issue of BMW OBDII readiness monitors not showing up, drawing from real-world experiences and providing insights into potential causes and solutions.
Understanding OBDII Readiness Monitors
OBDII (On-Board Diagnostics II) systems are integral to modern vehicles, continuously monitoring various engine and emission control systems. Readiness monitors are a crucial component of this system, designed to run self-tests and confirm that these systems are functioning correctly. These monitors must be in a “ready” or “complete” state for a vehicle to pass a smog check in many regions, including California.
Common readiness monitors include:
- Misfire Monitor
- Fuel System Monitor
- Comprehensive Components Monitor
- Catalyst Monitor
- Heated Catalyst Monitor
- Evaporative System (EVAP) Monitor
- Secondary Air Injection System Monitor
- Oxygen Sensor Monitor
- Heated Oxygen Sensor Monitor
- A/C System Refrigerant Monitor
When a monitor is “not ready,” it indicates that the system has not yet completed its self-test cycle. This can be due to various factors, ranging from recent battery disconnection to underlying mechanical or sensor issues.
The Frustration of the Missing EVAP Monitor: A Case Study
One BMW owner, driving a 1998 E36 M3, encountered the common problem of the EVAP system readiness monitor not setting, despite the absence of a check engine light and most other monitors being ready. This situation highlights a typical scenario where a driver might be perplexed – the car seems to run fine, yet a crucial monitor remains incomplete, potentially jeopardizing a smog check.
Initially, the driver’s experience involved extensive driving, including highway speeds and varying conditions, in an attempt to trigger the EVAP monitor to set. This involved:
- Cold Start: Allowing the car to sit overnight and starting it from a cold ambient temperature (around 60°F).
- Initial Idle: Extended idling for about 5 minutes after startup.
- Highway Driving: Maintaining a steady speed of 60 MPH for an hour.
- Stop and Start Cycles: Experiencing stop-and-go traffic and surface street driving at lower speeds (30 MPH).
- Cool Down Period: Letting the car sit for about 45 minutes after highway driving.
Despite these varied driving conditions, the EVAP monitor initially remained stubbornly “not ready.” It was only after a combination of highway and surface street driving, including stop-and-go traffic, that the monitor finally switched to “ready.”
Potential Reasons for BMW OBDII Monitors Not Ready
Several factors can contribute to OBDII readiness monitors, particularly the EVAP monitor, not showing up as ready on a BMW:
-
Driving Cycle Incompletion: Each readiness monitor has a specific “driving cycle” – a set of driving conditions that must be met for the self-test to run and complete. If these conditions are not precisely met, the monitor may not set. BMW driving cycles can be complex and sometimes require very specific combinations of speeds, durations, and temperature ranges.
-
Temperature Sensor Issues: The EVAP system monitor, and potentially others, can be temperature-sensitive. Faulty ambient air temperature sensors or engine coolant temperature sensors can prevent the monitor from running if the system doesn’t detect the correct temperature parameters. In the case study, a potentially inaccurate OBC (On-Board Computer) ambient temperature reading might have initially hindered the EVAP monitor from setting.
-
Underlying System Faults (Even Without a Check Engine Light): While a check engine light (CEL) usually indicates a problem, some minor faults or conditions might prevent readiness monitors from setting without triggering a CEL. These could be subtle leaks in the EVAP system, minor sensor discrepancies, or issues that are borderline enough not to trigger a fault code but still disrupt the readiness test.
-
Recent Battery Disconnection or Code Clearing: If the car battery has been recently disconnected or diagnostic trouble codes (DTCs) have been cleared with a scan tool, all readiness monitors will reset to “not ready.” It then requires completing the necessary driving cycles for each monitor to reset.
-
Aftermarket Modifications: In some cases, modifications like fan delete kits or aftermarket thermostats, as mentioned in the original experience, could potentially affect engine operating temperatures and influence the conditions required for readiness monitors to run. While not always the cause, they are worth considering, especially if temperature-related monitors are persistently not ready.
Troubleshooting Steps for BMW OBDII Monitors Not Showing Up
If you are facing the issue of BMW OBDII readiness monitors not showing up, here are some troubleshooting steps you can take:
-
Perform a Proper Driving Cycle: Consult your BMW owner’s manual or reliable online resources for the specific driving cycle recommended for your model and the monitor in question. Follow these instructions precisely. Generic driving cycles are available, but BMW-specific cycles are often more effective.
-
Check for Diagnostic Trouble Codes (DTCs): Use an OBDII scanner to check for any pending or stored DTCs, even if the check engine light is off. Address any codes found, as they can directly prevent readiness monitors from setting.
-
Inspect Temperature Sensors: If you suspect temperature sensor issues, use a diagnostic scanner to check the readings of the ambient air temperature sensor and engine coolant temperature sensor. Compare these readings to expected values. Faulty sensors may need replacement.
-
EVAP System Leak Test: Consider having a professional perform an EVAP system leak test, especially if the EVAP monitor is the one not setting. Even small leaks can prevent the monitor from completing.
-
Allow Sufficient Time: Readiness monitors, especially EVAP, can take time and multiple driving cycles to set. Be patient and allow for several drive cycles before concluding there is a more serious issue.
-
Consider California’s “One Monitor Not Ready” Rule: If you are in California or a similar region with lenient smog check rules, be aware that in many cases, you are allowed to have one readiness monitor “not ready” and still pass a smog check. The original poster in the case study was able to pass despite the Secondary Air Injection System monitor remaining incomplete. Check your local regulations.
Conclusion
Dealing with BMW OBDII readiness monitors that are not showing up can be perplexing. By understanding the function of these monitors, recognizing potential causes, and following systematic troubleshooting steps, BMW owners can effectively address this issue. In many cases, a proper driving cycle or addressing minor sensor issues can resolve the problem. Remember to consult reliable repair information specific to your BMW model and, when necessary, seek professional diagnostic assistance to ensure your vehicle is ready for emissions testing and optimal performance.
