Accelerator Pedal Position Sensor 2 Circuit High (GM)
What does P1223 mean?
The P1223 code means the vehicle's onboard diagnostic system has detected: Accelerator Pedal Position Sensor 2 Circuit High (GM). This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Reduced Engine Power warning
- Vehicle may not accelerate properly
- Limp mode activation
- Erratic throttle response
Probable Causes (Ranked by Likelihood)
- Faulty accelerator pedal position (APP) sensor Very High
- Short to power in APP sensor 2 wiring High
- Corroded APP sensor connector Moderate
- 5V reference voltage issue Moderate
- PCM input circuit failure Low
Step-by-Step Diagnostic Procedure
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Read APP sensor 1 and APP sensor 2 values on a scan tool
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Check that both APP sensor readings change smoothly with pedal movement
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Measure the 5V reference and ground at the APP sensor connector
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Inspect the connector for corrosion, especially at the foot well area
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Replace the accelerator pedal assembly if the sensor is faulty
Frequently Asked Questions
What is the accelerator pedal position sensor?
Modern vehicles with electronic throttle control use sensors on the gas pedal to measure how far you press it. The PCM uses this signal to control the electronic throttle body. Most systems have two sensors for redundancy.
Can I replace just the sensor?
On most GM vehicles, the APP sensors are built into the accelerator pedal assembly and cannot be replaced separately. The entire pedal assembly must be replaced, which includes both sensors.
Is the reduced engine power dangerous?
Reduced Engine Power mode is a safety feature, not a hazard. It limits vehicle speed to prevent unintended acceleration if the throttle system is not working correctly. Drive slowly to a safe location or repair shop.