When it comes to Chevrolet vehicles, it is important to be aware of all the codes that could appear when something is wrong with the engine. The P1509 code is one such code, specifically indicating an issue with an idle speed that is running too high. Whenever the engine is started and the engine runtime is over two minutes and the engine coolant temperature (ECT) sensor is more than 132°F, the intake air temperature (IAT) sensor is more than 68°F, the vehicle speed is less than 3 mph with the throttle closed, and the powertrain control module (PCM) detects that the actual idle speed is more than 175 rpm than the desired idle speed, then the P1509 code will likely appear. If a vehicle is displaying this code, it is important to understand the potential causes and solutions so that the issue can be diagnosed and fixed quickly.
Causes and Solutions for P1509 Code
| Cause | Solution |
|---|---|
| Base engine problem (engine vacuum leak or PCV valve leak) | Check for vacuum leaks and replace PCV valve if necessary. |
| IAC motor is damaged or has failed (it may be sticking) | Replace the IAC motor. |
| IAC motor circuit open, shorted to ground or shorted to power | Check the IAC circuit for any issues and repair as necessary. |
| Throttle body adjustment screw tampered with or damaged | Check the throttle body adjustment screw, and replace if necessary. |
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