Code Definition

P0518 — ISC Circuit Intermittent

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0518

P0518 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0518 is stored, the module has detected an electrical-circuit fault in the wiring, connector, or driver associated with the named component.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0518 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The P0518 fault code is set when the Engine Control Module (ECM) detects intermittent signals or disruptions in the Idle Speed Control (ISC) circuit. The ISC system, also known as the Idle Air Control (IAC) system in some vehicles, regulates the engine's idle speed by controlling the amount of air bypassing the throttle plate. An intermittent fault in the ISC circuit can result in erratic idle behaviour, which might manifest as fluctuating, too high, or too low idle speeds. Causes of intermittent signals in the ISC circuit can include loose or corroded connections, damaged wires, a faulty ISC ...

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