Throttle Position Sensor Circuit Intermittent Low Voltage (GM)
What does P1122 mean?
The P1122 code means the vehicle's onboard diagnostic system has detected: Throttle Position Sensor Circuit Intermittent Low Voltage (GM). This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Reduced Engine Power warning
- Engine stalling at idle
- Jerky or hesitant acceleration
- Erratic idle speed
Probable Causes (Ranked by Likelihood)
- Worn or faulty throttle position sensor (TPS) Very High
- Intermittent open in TPS signal wire High
- Loose TPS electrical connector Moderate
- Carbon buildup on throttle body affecting TPS Moderate
- PCM connector corrosion Low
Step-by-Step Diagnostic Procedure
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Monitor TPS voltage on a scan tool while slowly opening the throttle
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Look for any sudden drops in voltage that indicate a dead spot
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Wiggle the TPS connector while monitoring voltage for signal dropout
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Clean the throttle body and check if symptoms improve
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Replace the TPS or throttle body assembly if dead spots are found
Frequently Asked Questions
What causes intermittent TPS voltage drops?
The most common cause is a worn carbon track inside the TPS. As the sensor ages, areas of the track wear thin, creating dead spots that cause momentary signal loss. A loose connector can also cause intermittent signal issues.
Can cleaning the throttle body fix P1122?
Sometimes. If carbon buildup is preventing the throttle blade from closing fully, cleaning can help. However, if the TPS itself has worn internal components, cleaning will not fix the issue and the sensor or throttle body needs replacement.
Is the TPS replaceable separately on GM vehicles?
On older GM vehicles, the TPS is a separate bolt-on sensor. On newer models with electronic throttle control, the TPS is integrated into the throttle body and requires replacing the entire assembly.