P2138 on Chevrolet: How to Diagnose & Fix
Throttle/Pedal Position Sensor D/E Voltage Correlation
4 Chevrolet models · 4 documented issues · 2 critical · $100-$700 repair
P2138 on Chevrolet by model: symptoms, diagnosis and fix
The 2007-2013 Avalanche frequently enters "Reduced Engine Power" mode, severely limiting acceleration. The most common causes are the electronic throttle body wearing out or the accelerator pedal position sensor (APP sensor) developing faults. The vehicle becomes barely drivable in this mode, struggling to accelerate to highway speeds. The issue can occur intermittently before becoming permanent.
Common Symptoms
- "Engine Power Reduced" or "Reduced Engine Power" message on dash
- Vehicle struggles to accelerate past 20-30 mph
- Check engine light with P2128 or P2138 codes
- Intermittent power loss that resolves after restart
- Rough or hesitant throttle response
How to Fix
Diagnose with a scan tool to determine if the throttle body or accelerator pedal position sensor is the cause. Throttle body replacement costs $200-$400 parts and labor. APP sensor replacement costs $100-$250. A remanufactured throttle body from a quality source works well. Clear codes after repair and road test to verify.
What you need to diagnose it
The repair instructions explicitly call for reading stored codes. Use a scanner that can read the named code families before choosing a repair.The recommended scanner supports these code families; confirm your exact year, model and module coverage before buying.
ANCEL AD310 Classic OBD-II Scanner
Read & clear engine (P) codes
$20–$40View
As an Amazon Associate, we earn from qualifying purchases. Prices are approximate and may vary.
Reading and clearing the code is DIY work. Module replacement or reprogramming is not — most modules are VIN-programmed, so a new one does nothing until a shop codes it to your car. Check for an open recall or service bulletin before buying anything.
Sources for this issue (1)
The GMT360 TrailBlazer uses a drive-by-wire throttle actuator control system with dual redundant sensors in both the throttle body and the accelerator pedal. When the two throttle position signals disagree the PCM sets P2135 and drops the truck into Reduced Engine Power limp mode — the vehicle will barely accelerate, which is dangerous when it happens pulling into traffic. Usual root causes are an internally failed electronic throttle body, a corroded or loose crimp in the throttle body connector, or moisture intrusion in the harness. Related codes P0641 (5V reference) and P1523 (throttle closed position performance) show up alongside it.
Common Symptoms
- 'Reduced Engine Power' message on the dash
- Vehicle will barely accelerate / limp mode
- Check engine light with P2135
- Rough or hunting idle
- Intermittent stall or no throttle response
How to Fix
Do not simply throw a throttle body at it. Inspect the throttle body connector terminals for a loose crimp between the terminal and the copper strands and for green corrosion — a widely reported fix on this platform. Clean carbon from the throttle bore, since heavy buildup causes P1523. If the two TPS signals still fail to track on a scan tool, replace the electronic throttle body assembly (roughly $150-400 for the part) and relearn idle. If pedal position codes appear instead, the accelerator pedal position sensor assembly is the culprit. No recall covers this.
Sources for this issue (3)
A widely reported Silverado 1500 complaint is a sudden cascade of dash messages — 'StabiliTrak disabled,' then 'Service StabiliTrak,' 'Service Traction Control,' and finally 'Engine Power Reduced' — sometimes with a stumble or stall and limited throttle response. The most common root causes are a faulty accelerator pedal position (APP) sensor or throttle body (electronic throttle), but it is also frequently traced to poor/corroded ground connections and chafed wiring under the driver's door sill or at the underseat/main harness connector. Because it can drop the truck into reduced-power limp mode at speed, owners treat it as urgent.
Common Symptoms
- 'Service StabiliTrak' and 'Service Traction Control' messages
- 'Engine Power Reduced' / limp mode
- Throttle becomes unresponsive or truck stalls
- Multiple ABS/traction/stability lights at once
- Symptoms come and go (intermittent)
How to Fix
Scan for stored codes (commonly P2138 and related APP/throttle codes) and read live throttle/pedal data. Start by inspecting and cleaning the body grounds under the driver's door and the main harness connector (a known fix), then test/replace the APP sensor or throttle body as indicated. Apply any GM throttle-body or PCM software updates. Confirm the actual failed component before replacing the throttle body, as wiring/ground faults mimic sensor failure.
What you need to diagnose it
The repair instructions explicitly call for reading stored codes. Use a scanner that can read the named code families before choosing a repair.This issue involves C codes, which a basic engine-code reader cannot see.The recommended scanner supports these code families; confirm your exact year, model and module coverage before buying.
Autel MaxiCOM MK808S Diagnostic Tool
All-system diagnostics (25+ modules)
$350–$450View
As an Amazon Associate, we earn from qualifying purchases. Prices are approximate and may vary.
Reading and clearing the code is DIY work. Module replacement or reprogramming is not — most modules are VIN-programmed, so a new one does nothing until a shop codes it to your car. Check for an open recall or service bulletin before buying anything.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Accelerator pedal assembly with position (APP) sensor — 2014-2018 (K2XX generation)OEM23362231Cross-refDorman 699-213, A-Premium APP pedal (Amazon B0CFXK98R8, lists 2014-2018 Silv, GM 20972082 (superseded by 23362231)$86–$162
Only replace after confirming P2138/P2122-type codes are not caused by the door-sill body grounds or the underseat harness connector — c
- Electronic throttle body with sensor — 4.3L V6 (LV3), 2014-2021OEM12676296Cross-refGM 12632171 / 12671014 / 12669536 / 12648414 (all superseded, Standard Motor Products / Dorman aftermarket units sold as 2$100–$295
4.3L-only throttle body; do not use the V8 part. 2022 Silverado 1500 with 4.3L is not shown on the GMPartsGiant fitment (listed 2014-2021) — a 2022 4.3L owner should confirm by VIN.
- Electronic throttle body with sensor — 5.3L V8 (L83 / L84), 2014-2022OEM12713775Cross-refGM 12740725 (current supersession of 12713775), GM 12617792 (earlier 5.3L number cross-referenced by afterma, A-Premium / ADIGARAUTO aftermarket units listing OE 12617792$200–$359
Confirm the failed component with live TPS/APP data first; grounds and chafed underseat harness wiring are
- Electronic throttle body (87mm) — 6.2L V8 (L86 / L87), 2014-2021OEM12740727Cross-refGM 12678223 / 12729495 / 12733469 / 12620263 / 12713774 (all, GM 12678312 (2019-2021 6.2L listing on GMPartsGiant, itself $80–$200
6.2L uses the 87mm LT-family throttle body shared with Corvette/Camaro LT1 — not interchangeable with the 5.3L unit.
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Sources for this issue (1)
The Cobalt is drive-by-wire: the pedal module houses two redundant APP sensors, and the PCM compares them against the electronic throttle body's two TPS signals. When one signal drifts out of correlation the PCM drops the car into Reduced Engine Power mode — throttle authority is cut to a fast idle with the wrench/RE POWER message on the cluster, often with no warning in traffic. Owners report it as an intermittent that starts as a stumble and progresses to repeated limp events. P2138 (APP sensor 1-2 correlation) is the dominant code. The real cause is split between a worn pedal module, a dirty or failing electronic throttle body, and — very commonly on this car — corroded or loose connector terminals, since water intrusion down the A-pillar from a clogged sunroof drain reaches wiring in this area.
Common Symptoms
- "Engine Power Reduced" message on the cluster
- Sudden loss of acceleration in traffic
- Wrench warning light
- Rough or surging idle
- Intermittent hesitation that clears after a restart
How to Fix
Read the code before buying parts. Back-probe and inspect the pedal connector and the throttle body connector for green corrosion, spread terminals, or a loose lock — a bad terminal mimics a failed sensor and is the cheapest fix. If the terminals are clean, scope or graph both APP signals while sweeping the pedal to see which one drops out. A carbon-fouled throttle body responds to cleaning plus an idle relearn; if the fault follows the pedal, replace the accelerator pedal module (often cheaper than the throttle body and the more common culprit). Perform the throttle-position relearn after any replacement.
Sources for this issue (4)
P2138 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P2138 mean on a Chevrolet?
P2138 stands for "Throttle/Pedal Position Sensor D/E Voltage Correlation." This code means the two (or three) signals from the accelerator pedal position / throttle position sensors disagree with each other — specifically sensors 'D' and 'E', which are typically the redundant signals built into the electronic accelerator pedal. Drive-by-wire systems use multiple sensors that should track together so the computer can trust the driver's input; when their voltages don't correlate, the computer can't be sure of the requested throttle and sets this code. As a safety response it usually puts the engine into a reduced-power 'limp' mode. It generally points to the pedal sensor assembly or its wiring. On Chevrolet it is documented across 4 models: Avalanche, TrailBlazer, Silverado 1500, Cobalt.
What are the most common causes of P2138?
The most common causes of P2138 are: Faulty accelerator pedal position sensor assembly, Corroded or loose pedal sensor connector, Chafed, shorted, or open wiring between pedal and ECM, Shorted-together signal wires in the pedal harness, Poor sensor ground or reference voltage, Moisture or contamination in the pedal connector, Faulty ECM/PCM (less common). The specific cause varies by vehicle.
How much does it cost to fix P2138 on a Chevrolet?
Published repair estimates on Chevrolet range from $100 to $700 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P2138 on a different make?
View P2138 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.