Diagnostic Aids

Most solenoids leak a small amount of vacuum when closed; however, they should not leak enough to allow servo to reach WOT in 15 seconds with vent closed. When vacuum solenoid is forced on, vacuum will vent to atmosphere unless vent valve is stuck closed. A cruise control throttle cable which binds or intermittently sticks may cause vehicle to operate in power management and Code P1599 to set. Code P1599 can also be set by manually compressing cruise servo to raise engine speed.

Outside interference such as a CB antenna lead near PCM wiring harness may induce a false SPS signal and set Code P1599.