Exhaust Aftertreatment System Monitoring Incomplete (Generic)
The P4087 code means the vehicle's onboard diagnostic system has detected: Exhaust Aftertreatment System Monitoring Incomplete (Generic). This is a low severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- $0 - $150 (diagnosis only)
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Common Symptoms
- Check Engine Light on
- Aftertreatment readiness monitors not complete
- May fail emissions inspection
- No drivability issues
- Drive cycle not met
Probable Causes (Ranked by Likelihood)
- Insufficient driving to complete monitors Very High
- Intermittent sensor fault preventing completion High
- Software calibration needing update Moderate
- Battery disconnect resetting monitors Low
Step-by-Step Diagnostic Procedure
-
Drive vehicle through manufacturer-specified drive cycle
-
Check for other stored or pending codes
-
Verify all sensors are operating correctly
-
Check for TSBs related to monitor completion
Frequently Asked Questions
What does monitoring incomplete mean?
The PCM has not completed all the required tests on the aftertreatment system. This usually just requires driving the vehicle normally for a period.
Will P4087 fail emissions?
Yes, if readiness monitors are not complete, most states will fail the emissions inspection.
How do I complete the drive cycle?
Follow the manufacturer-specific drive cycle, which typically involves a mix of highway and city driving after a cold start.
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