Automotive Service Excellence (ASE) A8 Engine PerformanceComputerized Engine Controls Diagnosis and RepairEasy
A technician is performing a pre-purchase inspection on a vehicle. The Check Engine Light (CEL) is off, but the monitor status on the scan tool shows that the Evaporative Emission Control (EVAP) System monitor is 'Not Ready'. All other monitors are 'Ready'. What does this 'Not Ready' status indicate?
- AThe EVAP system has been intentionally disabled by a previous repair.
- BThe vehicle's PCM has not yet completed the self-test for the EVAP system.
- CThe vehicle is not equipped with an EVAP system.
- DThe EVAP system has a pending fault that has not yet illuminated the CEL.
Show answer & explanationAnswer & explanation
Correct answer: B. The vehicle's PCM has not yet completed the self-test for the EVAP system.
A 'Not Ready' status for an OBD-II monitor indicates that the Powertrain Control Module (PCM) has not yet completed the self-test procedures for that specific system. This is common after a battery disconnect or DTC clearing.
Why the other options are wrong
- A. It is illegal to intentionally disable an EVAP system, and the 'Not Ready' status does not imply intentional disabling.
- C. Most modern vehicles are equipped with an EVAP system; if it weren't equipped, the monitor might show 'N/A' or not be listed, not 'Not Ready'.
- D. A pending fault would typically show up in pending DTCs, not just as a 'Not Ready' monitor status.
OBD-II Monitor Readiness
OBD-II monitor readiness status indicates whether the Powertrain Control Module (PCM) has completed the self-diagnostic test for a specific emissions-related system since the last reset or battery disconnect.
- 'Ready' means the test is complete and passed.
- 'Not Ready' means the test has not yet run or completed.
- Required for emission inspections in many areas.
Memory trick: Monitors are like students: Ready, Not Ready, or Absent.