P2135 critical

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.

My Garage →
Keep driving?
No -- stop driving
DIY difficulty
hard
Estimated cost
$0 for throttle body cleaning; $150-$400 for throttle body replacement
Recommended Tool
ANCEL AD310 OBD-II Scanner

Best-selling code reader on Amazon. Reads and clears check engine codes on any 1996+ vehicle. Under $30.

Check Price on Amazon

Affiliate link -- we earn a commission at no extra cost to you.

Every Tech Needs This
AstroAI Digital Multimeter

Essential for diagnosing sensor codes, checking voltage, and testing circuits. Under $15 and pays for itself on the first job.

Check Price on Amazon

Affiliate link -- we earn a commission at no extra cost to you.

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

Step-by-Step Diagnostic Procedure

  1. Monitor TPS 1 and TPS 2 simultaneously on a scan tool. They should move in opposite and proportional directions through the full throttle range.

  2. Clean the throttle body and test again. Carbon can cause inconsistent readings.

  3. If TPS 1 and TPS 2 diverge or one stays flat, the throttle body needs replacement.

  4. Also monitor accelerator pedal position sensor 1 and 2 for correlation issues.

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.

Sources

This page is built from documented references. Verify against your own service info before repair work.

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:

Duramax serious Throttle/Pedal Position Sensor 'A'/'B' Voltage Correlation

Explore More

Search codes Vehicle-specific fixes Guides By make

Was this helpful?

Share carcodefinder.com with a friend who needs to decode their check engine light.

Browse by symptom → Read repair guides → Fixes by vehicle →