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.
System Outline
During idle stop or when all cylinders are deactivated, vacuum inside the intake manifold lowers.
Vacuum for the brake booster is monitored by PCM. Idle stop and cylinder deactivation takes place as long as there is sufficient vacuum.
- When the brake booster vacuum is less than the reference value, cylinder deactivation and idle stop will not occur.
- Cylinder deactivation and idle stop are monitored constantly and stopped by the PCM if it detects a failure. (Two sensors monitor mutually characteristic abnormalities.)
- The IMA indicator comes on when brake booster pressure sensor(s) fail.
The brake booster vacuum must reach the established point to ensure enough braking force to allow for auto idle stop activation. If the established value is decreased to the extent that braking force cannot be ensured, the engine will transition from auto idle stop to the engine idling.
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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.