Delay System (Heavy Duty All, and Light Duty California)

1. Check vacuum hoses for correct routing and valve installation, and that they are all in good physical condition.
2. Start engine and allow it to reach normal operating temperature, and set the parking brake.
3. Turn engine off.
4. Disconnect the EGR delay valve from the vacuum hose leading to the EGR control valve, and connect a vacuum gauge.
5. Start engine and increase engine speed to 2000 rpm. While watching the vacuum gauge, verify that there is no vacuum until 60 seconds have elapsed.
a. If there is no vacuum to this hose, then either the vacuum hoses or connections, or the EGR delay valve are defective.
b. If there is vacuum to this hose, but it takes less than a minute, then the EGR delay valve is defective and needs to be replaced.
c. If there is vacuum to this hose after 60 seconds, then the EGR delay system is completely functional.