P1220: APP Sensor Circuit C Low Input
The P1220 code indicates that the powertrain control module (PCM) has detected an abnormally low voltage on the 'C' circuit of the accelerator pedal position (APP) sensor. The APP system uses multiple potentiometers to monitor pedal position and ensure safety redundancy in electronic throttle control. A voltage below the expected operating range on circuit C suggests a signal interruption or a short to ground. This condition prevents the PCM from accurately calculating driver intent, typically resulting in restricted throttle response or activation of limp mode to protect the drivetrain.
01. Most Common Causes
- Faulty or internally damaged accelerator pedal position sensor
- Short to ground in the APP sensor circuit C wiring
- Open circuit or high resistance in the APP sensor connector
- Corroded, bent, or poorly connected terminals in the pedal harness
- Internal failure in the powertrain control module (PCM)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine power or limp mode activated
03. Step-by-Step Diagnosis
Scan for codes and verify P1220 is present
Inspect APP sensor connector and wiring for damage, corrosion, or loose pins
Test APP sensor circuit C voltage at the PCM connector with a multimeter
Compare APP sensor signals across all circuits for consistency
If wiring and sensor check out, test PCM for internal fault
1. Frequently Asked Questions
Is it safe to drive?▼
No, it is not safe to drive. The vehicle may enter limp mode with reduced power, increasing the risk of accidents or further damage.
How much does it cost to fix?▼
Repair costs typically range from $150 to $600, depending on whether the sensor, wiring, or PCM needs replacement.