Throttle Position Sensor 2 Circuit Malfunction (GM)
What does P1220 mean?
The P1220 code means the vehicle's onboard diagnostic system has detected: Throttle Position Sensor 2 Circuit Malfunction (GM). This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Reduced Engine Power message
- Poor throttle response
- Engine may idle high or low
- Vehicle may enter limp mode
Probable Causes (Ranked by Likelihood)
- Faulty throttle body with integrated TPS 2 Very High
- Wiring fault in TPS 2 circuit High
- Corroded TPS connector Moderate
- 5V reference voltage issue affecting TPS 2 Moderate
- PCM input circuit failure Low
Step-by-Step Diagnostic Procedure
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Read TPS 1 and TPS 2 values on a scan tool -- they should track inversely
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Check TPS 2 voltage sweep from closed to wide open throttle for dead spots
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Verify 5V reference and ground at the throttle body connector
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Inspect the connector for corrosion or loose pins
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Replace the throttle body if TPS 2 shows erratic readings
Frequently Asked Questions
Why do GM vehicles have two throttle position sensors?
Electronic throttle control systems use two TPS sensors for redundancy and safety. TPS 1 and TPS 2 provide opposing signals that the PCM compares. If they disagree, the system detects a fault and reduces power.
Can I replace just TPS 2?
On most GM vehicles with electronic throttle control, both TPS sensors are built into the throttle body and cannot be replaced separately. The entire throttle body assembly must be replaced.
Do I need to relearn the throttle body after replacement?
Yes. Most GM vehicles require a throttle body relearn procedure after replacement. This can be done with a scan tool or by following a specific key-on/key-off sequence outlined in the service manual.