P1516 on Chevrolet: How to Diagnose & Fix
Throttle Actuator Control (TAC) Module — Throttle Actuator Position Performance (GM)
3 Chevrolet models · 3 documented issues · 3 critical · $120-$500 repair
P1516 on Chevrolet by model: symptoms, diagnosis and fix
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)
The electronic (drive-by-wire) throttle system triggers a 'Reduced Engine Power' / 'Engine Power Is Reduced' limp mode that sharply limits acceleration and speed - dangerous when it strikes in traffic. The cause is usually the throttle actuator control (TAC): worn internal throttle-body sensors/motor, or a broken/chafed wire in the harness a few inches from the throttle-body connector. Correlation codes P2135 and TAC-performance code P1516 are typical.
Common Symptoms
- 'Reduced Engine Power' message and limp mode
- Sudden loss of acceleration
- Rough or surging idle
- Check engine light with throttle codes
How to Fix
Inspect the throttle-body connector and wiring first (the wires break near the plug); repair chafed wiring before replacing parts. If the throttle body itself is worn, replace it (GM 12570800 on 2003-2006 5.3L/6.0L trucks) and relearn the idle. Cleaning a carbon-fouled throttle body resolves milder cases. Some model years had extended special coverage on the accelerator-pedal/TAC system - check with a dealer.
Sources for this issue (1)
Tahoes with drive-by-wire throttle (APP pedal sensor + TAC module + electronic throttle body) commonly trigger a 'Reduced Engine Power' message and drop into limp mode with severely limited acceleration - a safety concern in traffic. On GMT800s the frequent culprits are a broken/chafed wire in the throttle-body harness (often the yellow wire), corroded engine grounds, or a dirty/sticking throttle body (P1516/P1515). GMT900s see similar throttle-actuator/APP faults (P2101/P2135/P0120 family).
Common Symptoms
- 'Reduced Engine Power' warning message
- Limp mode / severe loss of acceleration
- Hesitation or surging
- Check Engine light with throttle codes
- Intermittent power loss that clears on restart
How to Fix
Retrieve codes to isolate the branch: P1515/P1516 point at the TAC/throttle actuator, P2135/P0120-series at the TPS/APP correlation. Start with the cheap, common causes: clean the electronic throttle body, inspect and repair the throttle-body wiring harness (especially chafed/broken wires) and clean/tighten engine grounds. If the throttle body's internal TPS is faulty, replace the electronic throttle body assembly (ACDelco units available; part roughly $120-300). A failed APP pedal sensor is a less common cause.
Sources for this issue (1)
P1516 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 P1516 mean on a Chevrolet?
P1516 stands for "Throttle Actuator Control (TAC) Module — Throttle Actuator Position Performance (GM)." P1516 is a manufacturer-specific code used mainly by General Motors vehicles (Chevrolet, GMC, Buick, Cadillac, Hummer, Saturn), where it means the electronic throttle system's actual throttle plate position doesn't match what the computer commanded. In a drive-by-wire system, the ECM reads the accelerator pedal sensors and drives a motor on the throttle body to open the throttle; if the throttle position sensors report a position that disagrees with the command for more than about a second, this code sets. Drivers typically see a "Engine Power Reduced" message with the check engine light, and the vehicle drops into limp mode with sluggish, limited acceleration; some trucks set the code with no symptoms at all. Because throttle control directly affects your ability to accelerate, it should be diagnosed promptly rather than driven around. Note that the definition differs by manufacturer: Ford uses P1516 for an Intake Manifold Runner Control (IMRC) input error on Bank 1, while Honda/Acura use a throttle actuator position definition similar to GM's. On Chevrolet it is documented across 3 models: Cobalt, Suburban, Tahoe.
What are the most common causes of P1516?
The most common causes of P1516 are: Faulty throttle body / throttle actuator motor (the most common fix on GM trucks and SUVs), Dirty or carbon-fouled throttle body causing the throttle plate to stick or move erratically, Poor engine ground connections (corroded GM ground points G103/G104 causing voltage drop above 0.1V), Damaged wiring or corroded connectors in the TAC motor control or throttle position sensor circuits, Faulty throttle position sensor(s) on the throttle body, Failed stand-alone TAC module (separate module on 1999–2005 GM trucks), ECM/PCM fault, or a needed throttle relearn after cleaning or battery disconnect. The specific cause varies by vehicle.
How much does it cost to fix P1516 on a Chevrolet?
Published repair estimates on Chevrolet range from $120 to $500 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.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.