Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation
The P2135 code means the vehicle's onboard diagnostic system has detected: Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation. This is a critical severity code.
- Keep driving?
- No — stop driving
- DIY difficulty
- hard
- Estimated cost
- $0 for throttle body cleaning; $150-$400 for throttle body replacement
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Common Symptoms
- Reduced Engine Power light on
- Limp mode
- Unresponsive throttle
- Possible stalling
Probable Causes (Ranked by Likelihood)
- Failed throttle body with mismatched TPS signals High
- Carbon buildup causing TPS 1 and TPS 2 signals to diverge High
- Wiring fault causing signal corruption on one TPS circuit Moderate
- Failed accelerator pedal position sensor Moderate
Frequently Asked Questions
Why does P2135 put my car in limp mode?
Modern drive-by-wire systems use two independent throttle position sensors for redundancy and safety. If their signals do not correlate (agree), the ECU cannot trust either reading and enters reduced power mode as a safety precaution.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Monitor TPS 1 and TPS 2 simultaneously on a scan tool. They should move in opposite and proportional directions through the full throttle range.
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Clean the throttle body and test again. Carbon can cause inconsistent readings.
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If TPS 1 and TPS 2 diverge or one stays flat, the throttle body needs replacement.
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Also monitor accelerator pedal position sensor 1 and 2 for correlation issues.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
P2135 on Diesel, EV & Equipment
The same code ID appears across other engines and platforms. The diagnostic flow varies by manufacturer — these are the platform-specific breakdowns:
Commonly Affected Vehicles
- Chevrolet Cobalt, Malibu, HHR (2.2L, 2.4L Ecotec)
- Pontiac G6 and Solstice
- Saturn Ion
- Chevrolet Silverado and Tahoe (V8)
Related Codes
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