Idle Speed Control (ISC) Valve Test

After stopping engine, clicking sound should be heard from ISC valve. If not, remove ISC valve and perform operation check.
Drain engine coolant. Disconnect 2 electrical connectors, 2 coolant by-pass hoses and air hoses. Remove 2 bolts and ISC valve body.
Apply battery voltage to dual-terminal connector. Grounding terminals S1, S2, S and S4 in sequence should cause valve to open. See Fig 1 battery voltage still connected, grounding terminals in reverse sequence (S4, S, S2 and S1) should cause valve to close. If not, perform resistance check.

Fig 1: Checking ISC Valve Operation Valve should open when voltage is applied in one direction & close when voltage is applied in reverse direction.
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Check resistance values of ISC valve. Check resistance with ignition off and ISC electrical connector disconnected. If resistance is not as specified in chart, replace ISC valve.

ISC VALVE RESISTANCE SPECIFICATIONS

Terminals	Ohms
B1 - S1 or S	10-30
B2 - S2 or S4	10-30