Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Readiness Test Status
During different parameters of engine operation, the ECM/PCM monitors and runs tests on various inputs, outputs and system functions. There are 6 monitors. One monitor (Other Monitor) passively monitors for shorts, grounds and out of range parameters. It runs continuously. The other 5 monitors actively test different systems and will only run when very specific engine operating conditions have been met. Those monitors may or may not run during any given drive cycle. These 5 monitors have a system readiness test to show whether the particular monitor has been run or not. For additional information on drive cycles, see VERIFYING REPAIRS . A system related Diagnostic Trouble Code (DTC) cannot set until it's monitor has run successfully and readiness test status indicates COMPLETE.
When DTCs are cleared, each readiness test status is set to INCOMPLETE or NOT READY. To complete readiness test status, OBD-II drive cycles related to all on-board diagnostic items should be carried out. See OBD-II DRIVE CYCLES . If vehicle is normal, readiness test status will complete by carrying out OBD-II drive cycle once. MUT-II scan tool will then read COMPLETE. Generic scan tool will read READY. If ECM/PCM detects a malfunction, OBD-II drive cycle must be carried out again before readiness test status will complete. Once readiness test status is complete, ECM/PCM can be checked for DTCs.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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