Before idle speed/IAC duty is checked or adjusted, ensure all wires and vacuum hoses are connected securely, accelerator cable has free play, valve clearance and timing are set to specification and all accessories are turned off. Ensure transmission is in Park (A/T) or Neutral (M/T), battery voltage is 11 volts or greater and throttle valve moves smoothly.
Allow engine to reach normal operating temperature. Connect tachometer. Using a jumper wire, connect monitor connector terminal "D" (ground) to terminal "B" (diagnostic switch). Connect duty meter between terminal "D" (ground) and terminal "F" (duty output). See Fig 1 .
Ensure ISC duty varies in accordance with engine load. See the ISC DUTY SPECIFICATION table. Turn ignition off and allow engine to cool. Ensure ISC actuator moves when ignition is turned on. If plunger does not move and ISC duty is not within specification, see DTC P0505 in TESTS W/CODES article.

Fig 1: Inspecting ISC Duty

Courtesy of SUZUKI OF AMERICA CORP.

ISC DUTY SPECIFICATION

Engine Load	ISC Duty Increase Percentage
Electrical Load	About 3.5
Radiator Fan	About 3.5
A/C	About 10

NOTE: DO NOT remove ISC actuator from throttle body; it is adjusted by manufacturer.

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.

Safety Warning

Idle Speed Control System: Notes