Dealer Quote Too High for P2101/P2135? Let’s Talk Real Fixes.
Quick Answer
Problem: Codes P2101 (Throttle Actuator Control Motor Performance) and P2135 (Throttle/Pedal Position Sensor/Switch “A”/”B” Voltage Correlation) indicate a failure in the electronic throttle body assembly. This is a common failure point causing limp mode, stalling, or no acceleration.
Cost to Fix: $550 – $850. The GM throttle body assembly (Part # 12677809) costs $400-$500. Labor is 0.8-1.0 hours ($150-$350).
Time: Approximately 1 hour for diagnosis and replacement.
Actionable Advice: Do not attempt to clean the throttle body; replace the complete, non-serviceable assembly and perform the required throttle relearn procedure with a professional scan tool.
For specific year variations and engine codes, see the detailed sections below.
Symptoms
As a master technician, when a Silverado presents with both P2101 (Throttle Actuator Position Performance) and P2135 (Throttle/Pedal Position Sensor/Switch “A”/”B” Voltage Correlation), the root cause is typically a fault within the electronic throttle body assembly. Here are the specific symptoms you will likely experience:
- Reduced Power Mode / Limp Home Mode: The most immediate symptom. The engine power will be severely limited, often with RPMs capped at 1500-2000, and you will be unable to accelerate normally.
- Illuminated Check Engine Light with Service Traction Control/Stabilitrak Messages: The PCM will illuminate the CEL and often trigger secondary warnings for the stability systems due to the unreliable throttle signal.
- Erratic or Surging Idle: The engine may hunt for a stable idle speed, fluctuating between 500 and 1500 RPM, or may idle unusually high.
- Dead or Unresponsive Throttle Pedal: Pressing the accelerator pedal may produce no change in engine speed, or the response may be delayed and then suddenly engage.
- Vehicle Stalling at Stop or Upon Startup: The engine may stall when coming to a stop or immediately after starting, as the throttle body fails to maintain the correct idle air position.
- Harsh or Delayed Transmission Shifts: The TCM uses throttle position data for shift scheduling. Faulty signals can cause harsh, soft, or mistimed shifts.
The definitive repair is almost always replacement of the entire throttle body assembly (GM Part # 12681421 is common for many 5.3L/6.2L applications). Diagnosis and replacement typically takes 1.0 to 1.5 hours of labor, with the part costing between $280 and $450.
Diagnosis
Silverado P2101 & P2135 Diagnostic Guide
These codes indicate a Throttle Actuator Control (TAC) system throttle position (TP) sensor correlation fault. They almost always appear together and point to an issue with the electronic throttle body. Here is a systematic diagnostic approach:
- Initial Safety & Verification
Disconnect the battery for 5 minutes. Reconnect and clear codes. Start the engine and see if the codes return immediately or after a short drive. If they do, proceed with diagnosis. A common symptom is reduced engine power or a no-throttle response.
- Visual Inspection
Remove the engine air intake tube to access the throttle body (GM Part # often 12670290 or similar). Inspect the throttle plate for carbon buildup and check the wiring harness and connector (especially pins 1, 2, 5, & 6) for damage, corrosion, or pushed-out pins.
- Throttle Body Testing
With the connector unplugged and ignition ON, check for reference voltage (should be 5V) between pins 5 (Sensor 1) and 6 (Sensor 2) and their respective grounds (pins 1 & 2). If voltage is missing, a wiring or PCM issue is likely. If voltage is present, the internal sensors in the throttle body have likely failed.
- Common Fix
For 2007-2013 Silverados with the 4.8L, 5.3L, or 6.0L (LY5, LC9, L96, etc.), the throttle body is the most frequent culprit. A new GM throttle body assembly typically costs $280-$400 (e.g., GM Part # 12670290). Aftermarket units are available but can cause further issues. Labor is about 0.5 hours for replacement and a required relearn procedure.
- Relearn Procedure
After installation, you must perform a throttle body relearn. With a professional scan tool, this is under “TAC Module Reset” or “Throttle Learn.” Some models may allow a manual relearn: turn ignition ON (engine off) for 60 seconds, then turn OFF for 60 seconds. Start the engine and let it idle for 5 minutes.
- If Problem Persists
If codes return after a new throttle body, inspect the throttle body wiring harness all the way back to the PCM for chafing or damage. In rare cases, a faulty PCM (GM Part # varies by year) could be the cause, but rule out all wiring first.
Note: Do not attempt to clean the throttle body on a model with electronic throttle control (ETC) if these codes are set. Internal sensor failure is not repairable, and cleaning often makes the correlation fault worse.
Cost
| Component/Service | GM Part Number (Example) | Estimated Part Cost | Estimated Labor Hours | Total Estimate (Parts & Labor) | Notes |
|---|---|---|---|---|---|
| Throttle Body Assembly | 12677809 | $320 – $400 | 0.5 – 1.0 | $420 – $550 | Most common fix. Includes new TPS and throttle actuator. |
| Accelerator Pedal Position Sensor | 20986453 | $85 – $120 | 0.3 | $130 – $180 | Less common, but must be ruled out. Easy DIY. |
| Wiring Harness Repair | N/A (Service) | $50 – $150 (materials) | 1.0 – 2.5 | $200 – $450 | Required if chafing is found at the engine harness, often near the throttle body or ECM. |
| Diagnostic Fee | N/A | N/A | 1.0 | $120 – $180 | Typically applies if you don’t proceed with the repair at the same shop. |
| Typical Total Repair | 12677809 | $320 – $400 | 1.0 | $440 – $580 | This is the most likely scenario: replacing the throttle body. |
Critical Advice: Codes P2101 (Throttle Actuator Control Motor Performance) and P2135 (Throttle/Pedal Position Sensor/Switch “A”/”B” Voltage Correlation) almost always point to a failed throttle body on the Silverado. Do not just clear the codes. The truck will be in a reduced-power “limp” mode. After replacement, a throttle learn procedure (performed with a scan tool) is mandatory for correct operation.
*Note: These costs are 2026 estimates based on market research. Final repair costs will vary by location, shop rates, and vehicle condition. Always contact your local certified mechanic or dealer for an exact quote.
Fix
As a master technician, I can tell you that codes P2101 (Throttle Actuator Position Performance) and P2135 (Throttle/Pedal Position Sensor/Switch “A”/”B” Voltage Correlation) appearing together on your Silverado/Sierra almost always point to one culprit: a failing throttle body assembly. This is a very common failure on the 4.3L, 5.3L, and 6.2L GM V8 engines. Do not drive the truck; it will be in a reduced-power “limp” mode.
Here is the definitive step-by-step fix:
- Safety & Preparation
Disconnect the negative battery cable. This is critical as you will be removing the throttle body. Have a throttle body gasket (GM Part # 12677844) and throttle body cleaner (if attempting cleaning first) ready. - Remove the Air Intake Duct
Loosen the hose clamp at the throttle body and the airbox, then remove the entire plastic intake tube. This gives you clear access to the throttle body. - Inspect & Disconnect
Visually inspect the throttle body for excessive carbon buildup. Then, disconnect the electrical connector (press the tab and pull). - Remove the Throttle Body
Remove the four 10mm bolts securing the throttle body to the intake manifold. Carefully lift the throttle body straight off. Discard the old gasket. - Diagnostic Check (Critical Step)
With the throttle body removed, manually move the throttle plate by its gear. It should move smoothly with slight spring pressure. If it feels gritty, sticks, or is very loose, it has failed internally. This confirms the diagnosis. - Repair Decision
DO NOT ATTEMPT TO CLEAN AS A FIX. While you can clean the bore with throttle body cleaner and a soft cloth, the internal potentiometers (TPS sensors) that caused your codes are not serviceable. Replacement is the only reliable repair. - Install New Throttle Body
Install the new throttle body gasket. Install a new or GM-remanufactured throttle body assembly (Common GM Part # 12669790 for many 5.3L models, but ALWAYS verify with your VIN). Torque the four bolts to 89 in-lbs (about 7.5 ft-lbs) in a crisscross pattern. - Reconnect & Reassemble
Reconnect the electrical connector firmly. Reinstall the air intake duct and tighten all clamps. Reconnect the negative battery cable. - Relearn Procedure
Turn the ignition to ON (engine off) for 60 seconds. Then turn the key OFF for 60 seconds. This allows the ECM to relearn the new throttle body’s parameters. Start the engine—it may idle high for a few minutes, which is normal. - Clear Codes & Verify
Use your scan tool to clear the diagnostic trouble codes. Drive the truck normally for at least one drive cycle to verify the codes do not return.
Cost Estimate: A GM-remanufactured throttle body runs $220-$280. Labor is approximately 1.0 hour ($120-$150 at a shop). Total repair cost at an independent shop is typically $350-$450. A dealership will be higher. This fix resolves both codes in over 95% of cases on these trucks.
Prevention
The P2101 (Throttle Actuator Position Performance) and P2135 (Throttle/Pedal Position Sensor/Switch “A”/”B” Voltage Correlation) codes are classic symptoms of a failing throttle body assembly in Silverado trucks. The core strategy is preventative maintenance focused on the throttle body and its circuits.
- Regular Throttle Body Cleaning: Every 50,000 miles, clean the throttle bore and plate with a GM-approved cleaner (P/N 88861806). Avoid harsh scraping. This prevents carbon buildup that can cause the plate to stick and trigger correlation faults. Cost: ~$15 for cleaner + 0.5hr labor (~$50-$75).
- Inspect and Protect Electrical Connectors: Annually, check the throttle body connector and the accelerator pedal position (APP) sensor connector (under the dash) for corrosion, spread terminals, or loose fits. Apply dielectric grease to the seals to prevent moisture intrusion.
- Battery and Voltage Integrity: A weak battery or failing alternator can cause low-voltage conditions that the throttle body’s sensitive electronics interpret as a fault. Test battery health bi-annually and ensure charging voltage is stable at 13.5-14.5 volts.
- OEM Part Replacement: If failure occurs, use only a GM Genuine throttle body assembly. Aftermarket units have a high incompatibility rate. For a common 5.3L V8 (L83, L8B), expect part P/N 12681421 or equivalent. Part Cost: ~$350-$450. Labor: ~0.8hr (~$120-$160). Always perform a throttle relearn with a scan tool after replacement.
- Avoid “Quick Fix” Sensor Replacement: The P2135 code points to the internal Throttle Position Sensor (TPS), which is non-serviceable separately from the throttle body motor. Do not waste time/money trying to replace just a sensor.
- Check for Technical Service Bulletins (TSBs): Some model years had updated throttle body calibrations or harness routing fixes. A dealer can check your VIN against relevant bulletins, which may involve a reflash at minimal cost.
The ultimate strategy is proactive cleaning and electrical care. When replacement is necessary, using the correct GM part and performing the required relearn procedure is critical to a lasting repair.
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Real Owner Discussions
“Dealer just quoted me $2,800 to replace the throttle body and pedal assembly on my 129k-mile truck for these codes, claiming both are shot, but I’m convinced they’re just replacing parts until the problem goes away.”
“Just rolled 85,000 miles on my ’19 and the dealer wants $2,800 to replace the entire throttle body and pedal assembly for these codes, claiming they can’t fix the wiring—absolute highway robbery for a sensor harness issue.”
*Real discussions sourced from Silverado owners online.
❓ Frequently Asked Questions
5 Common Silverado Questions on P2101 & P2135 Throttle Codes
Q1: I got a P2101 and P2135 together on my 2018 Silverado. The truck goes into “Reduced Engine Power” mode. What does this actually mean?
A1: These codes are a direct conversation from your truck’s computer. P2135 means there’s a disagreement (implausible signal) between the two throttle position sensor circuits. P2101 is the result—the Engine Control Module (ECM) has commanded “Reduced Engine Power” as a safety fail-safe. The throttle body is likely faulty. You’ll experience very limited throttle response and top speed until it’s repaired.
Q2: What’s the most common fix, and what’s the cost?
A2: The most common and correct fix is replacing the entire electronic throttle body assembly. A new GM OEM throttle body (Part # 12681421) typically costs between $280 and $350. Labor is about 0.5 to 1.0 hour. Total repair at a shop usually lands between $450 and $600 with parts, labor, and programming.
Q3: Can I just clean the throttle body instead of replacing it?
A3: No. These codes are for electronic sensor agreement failures, not carbon buildup on the throttle plate. Cleaning the bore will not resolve the internal sensor fault. Installing a new unit is the required repair. Attempting to clean it is a waste of time for these specific codes.
Q4: Do I need a professional scan tool to finish the repair?
A4: Yes. After installing the new throttle body, a throttle relearn procedure must be performed with a capable scan tool (like a GM MDI or a high-end aftermarket scanner). This calibrates the ECM to the new unit’s sensors. Simply swapping the part without the relearn will often result in the codes returning or poor idle quality.
Q5: Could it be just a wiring problem or a bad pedal sensor?
A5: It’s possible but less common. The P2135 specifically points to a fault within the throttle body itself. However, a technician should always inspect the wiring harness and connector at the throttle body for damage, corrosion, or chafing. A problem with the accelerator pedal position sensor would typically set different codes (like P2122 or P2127), not P2135.
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Not Professional Advice: SilveradoFix.com content is for informational and educational purposes only. We are not providing professional mechanical, legal, or financial advice. Always consult a certified mechanic before attempting any repairs.
Cost Estimates: All prices, part costs, and labor times are 2026 estimates based on market research and owner reports. Actual costs vary significantly by location, shop rates, and vehicle condition.
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