What Does P1559 Mean?
The throttle position sensor is not adapting correctly during idle speed control learning procedures. The PCM cannot properly calibrate the throttle body's idle position, affecting idle quality and response.
Common Causes
35%
Carbon buildup on throttle plate preventing proper closure
30%
Faulty throttle position sensor providing incorrect feedback
20%
Throttle actuator motor malfunction in electronic throttle systems
10%
Vacuum leaks affecting idle adaptation process
5%
PCM software requiring update or recalibration
Diagnostic Steps
1
Step 1: Inspect throttle body for carbon buildup and physically check throttle plate movement
2
Step 2: Perform throttle body cleaning and adaptation/relearn procedure per manufacturer specifications
3
Step 3: Monitor live data for throttle position sensor voltage through full range (should be 0.5-4.5V smooth sweep)
4
Step 4: Check for vacuum leaks using smoke machine or propane enrichment method
5
Step 5: If all mechanical checks pass, attempt PCM adaptation reset or verify software version
Estimated Repair Cost
$150 - $600
Parts + labor, varies by vehicle and location
The throttle position sensor is not adapting correctly during idle speed control learning procedures. The PCM cannot properly calibrate the throttle body's idle position, affecting idle quality and response.
The most common cause of P1559 (Idle Speed Control Throttle Position Adaption Malfunction) is: Carbon buildup on throttle plate preventing proper closure
Typical repair costs for P1559 range from $150 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
May cause unstable idle, stalling at stops, or poor throttle response. Vehicle is generally safe to drive but may stall unexpectedly.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1559 to identify the root cause.
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Quick Info
Category
Powertrain
System
Idle Speed Control / Electronic Throttle Control
Difficulty
Type
Manufacturer
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