Learn about monitor readiness at Joe's Drive Thru Smog Check Star Station.
Discover why your vehicle might fail a smog check at Joe's Drive Thru Smog Check Star Station.
Background on OBDII Monitors and Smog Checks
The On-Board Diagnostic II (OBDII) system, mandated for most vehicles from 1996 onwards, includes a series of monitors that continuously or periodically test emission-related components and systems. These monitors are crucial for Smog checks, particularly in states like California, where emissions testing is stringent. For 2000 and newer gasoline vehicles, all monitors must be in a "ready" state to pass, with exceptions for the EVAP monitor under certain conditions, as per EPA and California standards
Readiness monitors are categorized into continuous and non-continuous types. Continuous monitors, such as misfire monitoring, fuel system monitoring, and comprehensive component monitoring, run constantly while the engine is operating. Non-continuous monitors, including the catalytic converter, oxygen sensor (HEGO), and EVAP system, require specific driving conditions to complete their tests, often involving predefined drive cycles
Detailed Causes of Not Ready Monitors
The failure of a Smog check due to not ready monitors stems from several underlying causes, each affecting the ability of the OBDII system to complete its diagnostic routines. Below is a detailed breakdown:
1. Battery Disconnection or Replacement
- Description: Disconnecting the battery, such as during a jump start or replacement, erases the Powertrain Control Module (PCM) memory, resetting all monitors to a "not ready" state. This is a common occurrence, especially after maintenance or battery failure.
- Impact: All monitors, both continuous and non-continuous, must be rerun, which can take days or weeks depending on driving patterns.
- Example: A vehicle owner who replaced their battery might find all monitors reset, requiring a drive cycle to restore readiness (https://www.joessmogcheck.com/post/not-ready-smog-check-failures).
2. Clearing OBDII Monitors with a Scan Tool
- Description: Using a scan tool to clear DTCs resets the monitors, similar to a battery disconnect. This is often done to address check engine light issues but inadvertently affects monitor readiness.
- Impact: Monitors must be driven through specific conditions to complete, and this process can be delayed if the car isn't driven appropriately post-clearing.
- Technical Note: On most vehicles, clearing DTCs does not automatically reset readiness monitors, but it can trigger a need for re-evaluation, especially for non-continuous monitors.
3. Insufficient or Improper Driving
- Description: Non-continuous monitors require specific driving conditions to run, such as reaching certain speeds (e.g., 45-65 mph for EVAP), maintaining temperatures, and completing multiple drive cycles. If the car is driven short distances or in a monotonous pattern, these conditions may not be met.
- Impact: Monitors like the catalyst efficiency monitor may need highway speeds for 10-15 minutes, and the EVAP monitor might require the car to sit for 8+ hours before a test drive , [Ask the Ref](https://asktheref.org/information/monitor-readiness-concerns/).
- Example: A vehicle driven only for short commutes might fail because the catalyst monitor never completed, despite no faults.
4. Vehicle Modifications or Faults
- Description: Modifications such as removing the catalytic converter, disconnecting sensors, or installing performance tunes can prevent monitors from running. Additionally, under-performing components, like an oxygen sensor with a minor leak, might prevent monitor completion without setting a DTC.
- Impact: Specific monitors, such as the catalyst efficiency monitor, cannot run if the converter is removed, leading to a not ready state. Faults like exhaust leaks can affect oxygen sensor performance, hindering Catalyst monitor completion.
- Legal Note: Removing emission components is illegal for street-driven vehicles and will result in Smog check failure.
5. Recent Computer Updates or Issues
- Description: Updates to the vehicle's computer system or issues like pending check engine light conditions can reset or affect monitor readiness. This is less common but can occur during software updates or if the PCM has unresolved issues.
- Impact: Monitors may not run to completion if the computer is in a state of update or error, requiring diagnostic intervention.
- Example: A vehicle with a recent ECM update might show not ready monitors, necessitating a drive cycle post-update.
Specific Monitor Requirements and Conditions
To provide clarity, below is a table detailing specific monitors and their readiness requirements:
Monitor | What It Checks | Conditions to Set |
Catalyst | Efficiency of the catalytic converter | Drive at 50-60 mph on the highway for 10-15 minutes after the engine is warm. |
Evaporative System (EVAP) | Fuel vapor leaks | Cold start, then idle for 2-3 minutes; drive at 40-60 mph for 5-10 minutes. |
O2 Sensor | Oxygen sensor performance | Steady driving at 50-60 mph for 5-10 minutes; avoid sudden stops or acceleration. |
EGR System | Exhaust gas recirculation | Mix of city driving (25-35 mph) and idling; may take multiple short trips. |
Misfire | Engine misfires | Normal driving (city and highway) for 10-20 minutes; keep engine running smoothly. |
Fuel System | Air-fuel mixture | Steady driving at moderate speeds (40-60 mph) for 5-15 minutes. |
Note: Not all vehicles have every monitor, and some (like EVAP) can take longer to set. Check your manual or call us for specifics!
Regional Variations and Standards
The number of monitors allowed to be not ready varies by region and vehicle age. For instance:
- EPA Standards: 1996-1999 vehicles can have up to 2 monitors not ready; 2000+ vehicles can have 1 monitor not ready.
- California Standards: 2000+ gasoline vehicles require all monitors ready, except EVAP can be not ready, while diesel vehicles have different rules.
Practical Solutions and Recommendations
To address not ready monitors, vehicle owners should:
- Follow manufacturer-specific drive cycles, which can be found in the service manual or online resources.
- Follow Joe's Drive Thru Smog Check Star Station generic drive cycle procedures, which can be found at (https://www.joessmogcheck.com/post/not-ready-smog-check-failures).
- Ensure regular driving, including highway speeds and varied conditions, to meet monitor requirements.
- Avoid unnecessary battery disconnections or code clearings close to Smog check dates.
- Consult a mechanic if monitors remain not ready after extensive driving, as there may be underlying faults preventing completion.
Smog check failures due to not ready monitors are preventable with proper vehicle maintenance and driving practices. By addressing battery issues, ensuring adequate driving conditions, and avoiding modifications that affect monitors, owners can improve their chances of passing. For persistent issues, professional diagnosis is recommended, leveraging tools and expertise to identify and resolve underlying causes.
Joe’s Drive Thru Smog Check Star Station
10909 Burbank Blvd
North Hollywood, Ca 91601