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.
Theory Of Operation
The purpose of the shut down timer diagnostic is to determine if the Powertrain Control Module (PCM) internal clock is running as expected. This engine off timer is used as an enable condition for various OBD monitors. The rationality test consists of two tests used to evaluate shut down time.
During an initial engine start, if it is determined that the engine start is a cold start (determined by comparing the engine coolant temperature versus ambient temperature), the
Slow Test
will be run and a long shut down time would be expected. If it is determined that the engine start is not a cold start, the
Fast Test
will be run and a short shut down time is expected because the engine has not been cooled down to cold start conditions.
- The P1607 DTC will set if the Slow Test diagnostic runs and fails.
- The P2610 DTC will set if the Fast Test diagnostic runs and fails.
NO RELATED
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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.