P2125 on 2007-2011 Chevrolet Silverado: Reduced Power, Causes, and Fixes

What's Unique About the 2007-2011 Chevrolet SILVERADO

For this generation of GM trucks (GMT900 platform), a primary cause for P2125 is poor electrical contact in the accelerator pedal's connector. GM issued a specific Technical Service Bulletin (TSB #PIP3783D) advising technicians to inspect for poor terminal tension in the APP sensor circuits before replacing any parts. This means a simple connector 'wiggle test' could save you from buying a new pedal assembly 🎬 Watch this first to understand why the connector is often the culprit. you don't need. Forum users frequently report that unplugging, cleaning with contact cleaner, adding dielectric grease, and securely re-plugging the connector can sometimes resolve the issue permanently.

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 driver information center
• Check Engine Light or Service Engine Soon light is on
• Severely limited acceleration and sluggish throttle response
• Vehicle may not accelerate from a stop or may stall
• Vehicle speed may be limited to a very low value, sometimes as low as 5 mph
• Traction control or StabiliTrak warning lights may also illuminate

Most Likely Causes

1. Faulty Accelerator Pedal Position (APP) Sensor 🔴 High Probability → Shop Accelerator Pedal Assembly The internal electronics of the sensor, which is integrated into the pedal assembly, can fail over time, causing erratic or no signal. This is a widely reported failure item on GMT900 trucks.
   How to confirm: Using a scan tool, monitor the live data for APP Sensor 2 voltage while pressing the pedal. If the voltage jumps, drops out, or doesn't change smoothly, the sensor has failed. A good sensor's voltage should sweep smoothly with pedal movement.
   Typical fix: Replace the entire accelerator pedal assembly. The sensor is not sold separately. This is a simple DIY job requiring only a T30 socket and about 15 minutes. 🎬 See this walkthrough on how to replace the pedal assembly.
   Est. part cost: $60-$150
2. Poor Terminal Tension at the APP Sensor Connector 🟡 Medium Probability GM issued TSB #PIP3783D specifically for this issue, indicating it's a known problem where the female terminals in the connector become loose and don't make solid contact with the pins on the pedal sensor. The connector's location in the footwell makes it susceptible to being kicked or exposed to moisture from wet shoes.
   How to confirm: Visually inspect the connector for corrosion or damage. Perform a 'wiggle test' on the connector and harness while monitoring live sensor data; if the voltage reading changes or the code sets, you've found the problem. Gently tug on each wire at the back of the connector to check for an internal break.
   Typical fix: Repairing or replacing the connector pigtail. In some cases, simply ensuring the connector is fully seated and adding dielectric grease can resolve the issue. Some owners use a zip tie to keep the connector firmly seated.
   Est. part cost: $5-$30
3. Wiring Harness Damage ⚪ Low Probability The wiring harness in the driver's footwell can be damaged by moisture, abrasion from floor mats, or being kicked. In some GM vehicles with similar systems, wires have been found broken inside the loom where they rub against a valve cover or other engine components, which is difficult to see visually.
   How to confirm: Perform a continuity test on the signal, reference, and ground wires for the APP sensor between the pedal connector and the PCM. Check for chafing or rubbing points along the harness route.
   Typical fix: Repair the broken or shorted section of the wire harness. Protect the harness from future rubbing with loom or tape.
   Est. part cost: $1-$10

Rare But Worth Checking

• Poor Ground Connection: A loose or corroded ground wire, particularly the main engine-to-body or body-to-frame grounds (like G103 or G104 on the cylinder heads), can cause fluctuating reference voltages for multiple sensors, including the APP. One owner on a forum and a popular YouTube video traced a persistent 'Reduced Engine Power' issue to a single bad ground wire near the passenger side of the intake. Before replacing expensive modules, checking and cleaning all major ground connections 🎬 Watch this video to find the exact ground locations on your truck. is a worthwhile step.
• Water Intrusion in IP-to-Body Connector: A separate TSB for the related code P2138 (07-06-04-019F) notes that water can leak into the large IP-to-Body harness connector, often located in the driver's kick panel area. This can cause corrosion and short circuits for the APP sensor signals that pass through it. This is a known issue if you have signs of a water leak from the A-pillar or windshield.
• Powertrain Control Module (PCM) Failure: → Shop Engine Control Module (ECM) This is extremely rare. The PCM should only be considered after all other possibilities, including the sensor, all related wiring, and grounds have been definitively ruled out.

Diagnosis Steps

1. Read all diagnostic trouble codes with an OBD-II scanner. Note all codes present, especially P2138 or other APP-related codes.
2. As per TSB #PIP3783D, the first step is to inspect the accelerator pedal connector. Disconnect it, check for corrosion, moisture, or backed-out pins. Reconnect it firmly and clear codes to see if the problem returns.
3. Using a scan tool, view the live data for 'APP Sensor 1' and 'APP Sensor 2' voltage.
4. With the key on, engine off, slowly press the accelerator pedal to the floor and release it. Both sensor voltage readings should change smoothly and in correlation with each other. One should sweep up while the other sweeps down.
5. If the APP Sensor 2 ('E' circuit) voltage is stuck (often at 0V or 5V), erratic, or absent, perform a 'wiggle test' on the harness near the pedal while watching the live data. If the reading flickers, the wiring or connector is the fault.
6. If the wiring and connector are confirmed to be good, the APP sensor within the pedal assembly is faulty.
7. Replace the accelerator pedal assembly. This typically involves removing two T30 Torx bolts.
8. After replacement, clear the codes, and perform a test drive to confirm the fix. No special relearn procedure is typically required for this part.

Parts You'll Likely Need

• Accelerator Pedal Assembly (OEM #25832864) — This is the most common failure. The sensor is integrated into the pedal assembly and is not sold separately. This part number supersedes older numbers like 15847349 and 15101848.
  Trusted brands: ACDelco, GM Genuine Parts, Dorman (p/n 699-105)
  OEM price range: $95-$170
  Aftermarket price range: $50-$120

Related Codes That Often Appear With This One

• P2138 — This code for 'APP Sensor 1-2 Correlation' is very common with P2125 because it means the PCM is seeing conflicting signals from the two pedal sensors. A failure in one sensor (P2125) will cause it to disagree with the other, triggering P2138.
• P2120 — This is a general circuit fault for the APP Sensor 1 ('D' circuit). Seeing it with P2125 often points to a shared problem like a connector, power, or ground issue affecting the entire pedal assembly.
• P2122, P2123, P2127, P2128 — These are specific low and high voltage fault codes for APP Sensor 1 and 2. The TSB #PIP3783D groups all of these codes together as they share the same root causes and diagnostic path. P2127 (APP Sensor 2 Circuit Low) is a very common companion to P2125.

Technical Service Bulletins (TSBs) & Recalls

• PIP3783D: Advises technicians to inspect the Accelerator Pedal Position circuits for poor terminal tension when codes P2120, P2122, P2123, P2125, P2127, P2128, and/or P2138 are present, often with a 'Reduced Engine Power' message.

Platform-Specific Known Issues

• TSB #PIP3783D explicitly calls out poor terminal tension in the Accelerator Pedal Position circuits as a cause for P2125 and related codes, making a connector inspection the mandatory first step in diagnosis.
• The GMT900 platform is known for having ground issues that can cause strange electrical problems. A YouTube video by '737mechanic' with over 100k views shows how simply loosening and re-tightening the main engine grounds fixed a persistent 'Reduced Engine Power' issue on a 2011 Silverado.
• Water leaks near the A-pillar can drip onto the IP-to-Body harness connector in the kick panel, causing corrosion and leading to APP sensor codes.

Mechanic-Grade Diagnostic Values

• APP Sensor 2 Voltage (Scan Tool) — expected: 0.24V to 4.49V, changing smoothly with pedal input.. Failure: Voltage is less than 0.24V or more than 4.49V for more than 0.5 second.
• APP Sensor 2 5-Volt Reference Voltage (Scan Tool) — expected: Between 4.54V and 5.21V.. Failure: Voltage is outside the specified range, indicating a problem with the PCM or wiring.
• APP Sensor Connector Pinout (at pedal) — expected: Pin A: APP Sensor 2 Low Reference (GND), Pin B: APP Sensor 2 Signal, Pin C: 5V Reference 2, Pin D: APP Sensor 1 Low Reference (GND), Pin E: APP Sensor 1 Signal, Pin F: 5V Reference 1.. Failure: Continuity tests fail on any circuit, or voltage/ground is missing at the respective pins.

Wiring & Ground Locations

• G103 — On the front of the right (passenger side) cylinder head.. This is a primary engine ground. A poor connection here can cause unstable reference voltages for multiple sensors, including the APP sensor, leading to erratic readings and fault codes.
• G104 — On the rear of the left (driver side) cylinder head.. This is another critical engine ground. In some documentation, it is listed as being on the left front corner. It grounds several components, and a bad connection can lead to intermittent electrical issues that are hard to trace, sometimes mimicking sensor failures.
• ECM/THROT CONT Fuse — In the underhood fuse block, typically a 15A fuse labeled 'ECM/THROT CONT' or similar.. This fuse provides power to the throttle control system. Although a blown fuse would likely cause more severe issues than just P2125, it's a fundamental check in any electrical diagnosis for this system.
• APP Sensor Connector — The 6-pin electrical connector attached to the top of the accelerator pedal assembly inside the driver's footwell.. This is the most common point of failure due to poor terminal tension (as per TSB PIP3783D), physical damage from being kicked, or corrosion from moisture.

Real Owner Repair Stories

• YouTube channel '737mechanic' (2011 Chevrolet Silverado) — Reduced Engine Power message, codes P0220, P0222, P1516, and P2135.
  ❌ Tried (didn't work) Throttle Body Replacement, ECM (Engine Control Module) Replacement
  ✅ What actually fixed it The final fix was cleaning and tightening the main engine ground connections. The mechanic found that simply loosening and re-tightening the grounds on the back of the cylinder heads resolved the issue that expensive part replacements did not. A corroded battery ground cable was also replaced as a contributing factor.
• YouTube channel 'carquestions' (GM Truck (similar GMT900 platform)) — Reduced Engine Power, multiple codes.
  ❌ Tried (didn't work) Adding multiple redundant ground wires all over the engine bay.
  ✅ What actually fixed it The mechanic traced a specific ground wire on the passenger side of the intake manifold. He found the wire was broken internally right at the ring terminal connector. Simply tugging on the wire caused it to separate completely. Repairing this single broken ground wire by soldering on a new connection and grounding it securely fixed the persistent 'Reduced Engine Power' problem.

OEM Part Supersession History

• 15101848, 15847349 → 25832864 — Standard part revision and consolidation by the manufacturer.
  Heads up: The newest part number (25832864) is the correct replacement for the entire 2007-2011 range and is a direct fit. No programming is required after installation.