The Idle Speed Control Motor (ISC) is a precision DC motor managed by the vehicle’s engine control unit (ECU). It adjusts the throttle position during idle by moving a pintle (a small actuator) in and out to regulate airflow to the engine.
This process allows the ECU to maintain a steady idle speed under various engine loads — such as when the air conditioning, power steering, or electrical accessories are engaged — ensuring smooth and efficient operation.
How It Works:
- The ISC motor is electronically controlled by the ECU.
- It moves a pintle or valve that adjusts airflow past the throttle plate when the accelerator pedal is not pressed.
- The ECU monitors idle speed, engine load, and air intake, then commands the ISC to increase or decrease airflow as needed.
- Proper ISC function ensures consistent idle speed and smooth engine operation under all conditions.
Product Features & Benefits from Walker Products:
- Exact OE Fit: Direct replacement ensures accurate idle control and easy installation.
- OE Replacement Quality: Meets or exceeds original equipment performance standards.
- Durable Construction: Designed to withstand carbon buildup, vibration, and heat exposure.
- Restores Smooth Idle: Regains stable idle speed and consistent engine performance.
- Aftermarket Expertise: Backed by over 75 years of proven experience in precision engine management components.
Symptoms of a Failing Idle Speed Control Motor:
- Engine stalling or surging at idle.
- Irregular or rough idle speed.
- Engine may idle too high or too low.
- Check Engine Light (CEL) illuminated.
Common Check Engine Light (CEL) / OBD-II Codes
Since 1996, all vehicles have been equipped with OBD-II diagnostic systems to monitor emissions and performance. The codes below are commonly associated with Idle Speed Control Motors and should be used as a general guide only.
Walker Products will not be responsible for any use of this information. Always consult a qualified mechanic and follow manufacturer and EPA guidelines for diagnosis, replacement, and ECU/PCM relearn procedures.
- P0505 – Idle Air Control System
- P0506 – Idle Air Control System RPM Lower Than Expected
- P0507 – Idle Air Control System RPM Higher Than Expected
- P0508 – Idle Air Control System Circuit Low
- P0509 – Idle Air Control System Circuit High
- P050A – Cold Start Idle Air Control System Performance
- P050D – Cold Start Rough Idle
- P0511 – Idle Air Control Circuit
- P0518 – Idle Air Control Circuit Intermittent
- P0519 – Idle Air Control System Performance
- P2104 – Throttle Actuator Control System – Forced Idle
- P2176 – Throttle Actuator Control System – Idle Position Not Learned
- P2177 – System Too Lean Off Idle
- P2178 – System Too Rich Off Idle
- P2179 – System Too Lean Off Idle
- P2180 – System Too Rich Off Idle
- P2187 – System Too Lean at Idle
- P2188 – System Too Rich at Idle
- P2189 – System Too Lean at Idle
- P2190 – System Too Rich at Idle
- P256A – Engine Idle Speed Selector Sensor/Switch Circuit/Open
- P256B – Engine Idle Speed Selector Sensor/Switch Range/Performance
- P256C – Engine Idle Speed Selector Sensor/Switch Circuit Low
- P256D – Engine Idle Speed Selector Sensor/Switch Circuit High
- P256E – Engine Idle Speed Selector Sensor/Switch Circui