DTC 4431

^ Idle stabilizer valve. Idle stabilization control limits exceeded. This means that the idle stabilizer valve is receiving the maximum duty cycle and idle speed is still too low, or valve is receiving the minimum duty cycle and idle speed is still too fast.

This code may be caused by:

a. No battery power to terminal #2 of idle stabilizer valve, or open or grounded circuit between idle stabilizer valve terminal #1 and terminal #17 of ECU.
b. Idle stabilizer valve armature windings open or shorted (faulty valve).
c. Idle stabilizer valve stuck in one position, or binding limiting its range of motion (faulty valve).
d. "False air" (unmeasured air entering the intake manifold - vacuum leak).
e. Throttle not closing completely, sticking or binding.
f. Ignition timing (distributor position basic adjustment) retarded.
g. Restricted or plugged passage to (and/or from) idle stabilizer valve
h. Faulty differential pressure regulator, open or grounded circuit between differential pressure regulator terminals #1 and #2, and fuel control unit terminals #4 and #5 respectively.