P2135 on 2013 GMC Savana: Throttle Position Sensor Causes and Fixes

What's Unique About the 2013-2013 Gmc SAVANA

For this generation of GMC vans and trucks (GMT900 platform), the P2135 code is an extremely common and well-documented issue. GM issued a specific Technical Service Bulletin (TSB #11-06-04-007C) that advises replacing just the throttle position sensor cover and sensor assembly, rather than the entire throttle body. This makes the repair significantly cheaper than on other vehicles where the entire throttle body must be replaced. GM also acknowledged the high failure rate with a Special Coverage Adjustment (#11273A) that extended the warranty for the TPS to 10 years or 120,000 miles, though this has likely expired for most 2013 vehicles.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Reduced Engine Power message on the dashboard
🎬 Watch: How to diagnose the P2135 code and reduced power message.
• Vehicle enters 'Limp Mode' with severely limited acceleration
• Check Engine Light is on
• Unstable or rough idle
• Hesitation or surging during acceleration
• Engine may stall when coming to a stop
• Traction control or StabiliTrak warning light may also illuminate

Most Likely Causes

1. Failed Throttle Position Sensor (TPS) 🔴 High Probability → Shop Fuel Injection Throttle Body This is a widely recognized failure point on this GM platform, as documented in TSB #11-06-04-007C and Special Coverage #11273A. The internal circuits of the sensor degrade over time, causing the voltage signals to conflict.
   How to confirm: A professional scan tool can graph the voltage from TP Sensor 1 and TP Sensor 2. If one signal drops out or becomes erratic while the other is smooth, the sensor is faulty. However, the failure is so common that many technicians replace it based on the code alone.
   Typical fix: Replace the throttle position sensor kit (cover, sensor, clips) on the side of the throttle body. While doing so, it is best practice to clean the throttle body bore and plate. The TSB also recommends an ECM reprogram with the latest calibration, though many DIYers report success without this step.
   Est. part cost: $40-$115
2. Wiring Harness or Connector Issue 🟡 Medium Probability Engine vibration and heat can cause wires to fray or pins in the throttle body connector to develop 'fretting corrosion'. This is a type of wear from micro-vibration that degrades the electrical connection, causing intermittent signal loss. TSB PI P3089B specifically addresses this issue.
   How to confirm: Visually inspect the wiring harness leading to the throttle body for any signs of damage, chafing, or melting. Unplug the connector and check for corroded, loose, or backed-out pins. A 'wiggle test' on the harness while monitoring live sensor data can often duplicate the fault if a wire is broken internally.
   Typical fix: Repair the damaged section of wiring or clean the connector pins. If pins are heavily corroded or damaged, replace the connector pigtail. Applying dielectric grease during reassembly can help prevent future corrosion.
   Est. part cost: $15-$50

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM): → Shop Engine Control Module (ECM) This is very rare and should only be considered after the throttle position sensor and all related wiring have been definitively ruled out.
• Dirty or Binding Throttle Body: → Shop Fuel Injection Throttle Body While heavy carbon buildup can cause the throttle plate to stick, this typically won't cause a persistent electronic P2135 code. Cleaning is good maintenance but is unlikely to fix the code on its own if the sensor has failed.

Diagnosis Steps

1. Scan the vehicle for diagnostic trouble codes to confirm P2135 is the primary code.
2. Inspect the wiring harness and connector at the throttle body for any visible damage, chafing, corrosion, or loose pins. Pay close attention to where the harness may rub against engine components.
3. If possible, use a scan tool with live data capabilities to monitor the voltage readings of Throttle Position Sensor 1 (TP1) and Throttle Position Sensor 2 (TP2). As the throttle is slowly opened, both voltages should change smoothly and mirror each other. A drop-out, erratic reading, or divergence greater than 0.2V between the sensors indicates a fault.
4. Perform a 'wiggle test' on the throttle body harness for 1-4 inches from the connector while watching the live data to check for intermittent breaks inside the wire insulation, as suggested by TSB PI P3089B.
5. Given the high failure rate, if the wiring appears intact and the wiggle test shows no faults, the most likely cause is the TPS sensor itself.
6. Remove the throttle body from the intake manifold. On a Savana, this may require moving the alternator to gain access.
🎬 Watch: Accessing the throttle body on a Chevy Express or GMC Savana.
7. Replace the throttle position sensor cover/kit on the side of the throttle body assembly per TSB #11-06-04-007C. 🎬 See this walkthrough for replacing the throttle position sensor. Be careful not to damage the intermediate gear when the cover is off.
8. Thoroughly clean the throttle plate and bore with throttle body cleaner and a soft brush before reinstalling.
9. Reinstall the throttle body with a new gasket to prevent vacuum leaks.
10. Perform a throttle relearn procedure. A common method is to start the engine and let it idle for 3 minutes, turn it off for 60 seconds, then start it and let it idle for another 3 minutes.
11. Clear the trouble codes and test drive the vehicle to ensure the repair was successful. The TSB officially recommends a dealer reflash of the ECM, but this is often not required for a successful DIY repair.

Parts You'll Likely Need

• Throttle Position Sensor Kit (OEM #19259452) — This is the most common failure part for code P2135 on this vehicle, as identified by GM's own service bulletin.
  Trusted brands: ACDelco (OEM), Dorman (e.g., 977-000), Carquest Premium (e.g., ECC1009)
  OEM price range: $80-$120
  Aftermarket price range: $40-$95
• Throttle Body Gasket (OEM #12589235) — A new gasket should always be used when the throttle body is removed and reinstalled to prevent vacuum leaks. Some mechanics note the original gasket is often reusable if not damaged, but replacement is best practice.
  Trusted brands: ACDelco, Fel-Pro
  OEM price range: $10-$20
  Aftermarket price range: $5-$15

Related Codes That Often Appear With This One

• P1516 - Throttle Actuator Control (TAC) Module Throttle Actuator Position Performance
• P2101 - Throttle Actuator Control Motor Circuit Range/Performance
• P0120 - Throttle/Pedal Position Sensor/Switch 'A' Circuit
• P0220 - Throttle/Pedal Position Sensor/Switch 'B' Circuit

Technical Service Bulletins (TSBs) & Recalls

• 11-06-04-007C: Details the procedure for replacing the throttle position sensor cover, terminals, and gasket to resolve DTC P2135 and a 'reduced power' message. It explicitly warns not to replace the entire throttle body for this issue and recommends an ECM reprogram.
• PI P3089B: Addresses SES Light and Reduced Engine Power with DTC P2135, pointing to bad terminal crimps or broken wires near the throttle body connector.

Platform-Specific Known Issues

• GM issued Technical Service Bulletin #11-06-04-007C specifically for DTC P2135, which involves replacing the throttle position sensor cover.
• GM also issued Special Coverage Adjustment #11273A, extending the warranty on the TPS to 10 years/120,000 miles due to the high failure rate.
• Fretting corrosion on the throttle body connector pins is a known secondary cause that can mimic sensor failure.
• TSB PI P3089B points to poor terminal crimps or wires breaking inside the insulation within 1-4 inches of the throttle body connector as a key issue to investigate if a new sensor doesn't fix the problem.

Mechanic-Grade Diagnostic Values

• Throttle Position Sensor 1 (TP1) and Sensor 2 (TP2) Voltage Correlation — expected: Both sensor voltages should mirror each other and stay within 0.2V of each other throughout the throttle range.. Failure: A voltage difference greater than 0.2V between the two sensors for more than a few seconds will set the code.
• Throttle Position Sensor Voltage Range (Key On, Engine Off) — expected: Approximately 0.5V at closed throttle, sweeping smoothly up to approximately 4.5V at wide-open throttle.. Failure: Voltage that is erratic, jumps, or has dead spots as the throttle is slowly opened and closed.
• TP Sensor 1 Signal Circuit Voltage to Ground — expected: Less than 1.0V.. Failure: Voltage reading higher than 1.0V on the signal circuit (typically a Dark Green wire) can indicate a circuit fault.

Scan Tool Commands That Help

• Tech2 / GDS2 or equivalent professional scan tool: Idle Learn Reset — After replacing the throttle position sensor or throttle body, the PCM's learned values for the old part can cause a high or unstable idle. This function, found under 'Module Setup', forces the PCM to erase the old values and relearn the new sensor's baseline idle position, which can correct idle issues faster than a manual relearn procedure.

Wiring & Ground Locations

• Throttle Body Connector (X101) — Plugged directly into the throttle body assembly at the front of the intake manifold.. This is the single connection point for both TP sensors and the throttle motor. Corrosion, loose pins, or broken wires right at this connector are a primary cause of P2135, as detailed in TSB PI P3089B.
• Throttle Body Connector Pinout — On the main engine harness connector that plugs into the throttle body.. Knowing the pin functions allows for direct testing of each circuit. Typical pinout: Pin G: TP Sensor 1 Signal (Dark Green wire), Pin F: TP Sensor 2 Signal (Purple wire), Pin E: 5 Volt Reference (Light Blue/Black wire), Pin B: Low Reference/Ground (Black/White wire).
• Ground G103 — Typically located on the left (driver's side) rear of the engine compartment, on the cowl above the brake booster.. TSB PI P3089B suggests inspecting engine grounds as a possible cause for intermittent throttle-related codes. A poor ground can introduce electrical noise that affects sensor readings.
• Ground G102 — On the left rear of the engine block.. This is a primary ground for the ignition coils. While not directly for the TPS, a poor engine ground connection can cause a variety of difficult-to-diagnose electrical issues, including sensor correlation faults.

Real Owner Repair Stories

• CorvetteForum user (Corvette (similar GM electronic throttle system)) — Randomly entering 'Reduced Engine Power' mode with code P2135. The code would appear after starting the car and driving a short distance.
  ❌ Tried (didn't work) Replacing the accelerator pedal assembly, Replacing the throttle body assembly
  ✅ What actually fixed it The suggested fix, based on TSB PIP3089B, was to inspect the wiring harness for a bad terminal crimp or a wire broken inside the insulation, typically within 1-4 inches of the throttle body connector. Performing a 'wiggle test' on the harness while the engine is running is the key to finding this hidden fault.
• Chevy HHR Network user (2008 Chevrolet HHR 2.2L (similar GM electronic throttle system)) — Intermittent 'Engine Power Reduced' message, code P2135, usually occurring during a 1-2 upshift or when decelerating.
  ❌ Tried (didn't work) Cleaning the throttle body, Inspecting and cleaning PCM harness plugs
  ✅ What actually fixed it The problem was confirmed to be in the electrical harness. A dealer service technician replaced a bent or broken pin within one of the electrical plugs, which permanently resolved the intermittent connection issue.