Restore power and fix P003A/P0046 on your 2017–2019 Chevy Silverado or GMC Sierra 6.6L L5P Duramax with this remanufactured Synapse S79‑L5P1 turbo actuator. Ready‑to‑ship, pre‑programmed OEM‑fit replacement with 1‑year warranty and fast shipping from NorCal Diesel Performance.
This 2017–2019 Chevrolet/GMC 6.6L Duramax L5P remanufactured turbo actuator is a plug‑and‑play replacement for the factory electronic VGT actuator, supplied pre‑programmed to your L5P application. Designed to eliminate common trouble codes such as P003A and P0046 turbo control codes, “Reduced Engine Power” warnings, and sluggish spool‑up. Each unit is completely disassembled, rebuilt, and calibration‑tested on an actual turbocharger, so it bolts in place and is ready for dealer‑level calibration on the truck, restoring proper vane control, towing power, and exhaust brake performance.
This actuator is engineered specifically for the 2017–2019 GM L5P platform. It replaces the OE electronic turbo actuator bolted to the factory variable geometry turbocharger on these trucks.
Fits:
2017 Chevrolet Silverado 2500HD/3500HD 6.6L L5P Duramax
2018 Chevrolet Silverado 2500HD/3500HD 6.6L L5P Duramax
2019 Chevrolet Silverado 2500HD/3500HD 6.6L L5P Duramax
2017 GMC Sierra 2500HD/3500HD 6.6L L5P Duramax
2018 GMC Sierra 2500HD/3500HD 6.6L L5P Duramax
2019 GMC Sierra 2500HD/3500HD 6.6L L5P Duramax
100% direct‑fit for the factory L5P VGT turbo actuator on 2017–2019 Duramax trucks, using OE‑style mounting, connector, and output shaft, so there is no fabrication or wiring modification required.
Pre‑programmed specifically for L5P turbo geometry and control strategy, avoiding the headache of mismatched electronics or generic actuators that cannot be calibrated properly.
Each actuator is fully disassembled; worn mechanical components, seals, and electronic parts are replaced as needed, not just “cleaned and shipped.”
Circuit board solder joints and electronic components are inspected, repaired, or replaced, addressing known L5P actuator failure points such as thermal cycling damage and moisture intrusion.
Final calibration is performed on an actual turbocharger, verifying correct vane sweep, position feedback, and drive response before the unit ever leaves the reman facility.
Designed to eliminate common L5P turbo actuator issues such as:
P003A “Turbocharger/Supercharger Boost Control A Position Not Learned” or similar turbo position learning faults.
P0046 turbocharger boost control range/performance codes.
“Reduced Engine Power” messages, sluggish or rough turbo spool‑up, and situations where the turbo is not responding during acceleration.
By restoring precise vane control, the actuator helps recover low‑RPM torque, transient response, and exhaust brake functionality, especially noticeable when towing or driving in hilly terrain.
A failed actuator often triggers turbo‑related codes and limp‑mode behavior even when the turbocharger itself (shaft, wheels, housings) is still in good mechanical condition.
Replacing only the actuator with a high‑quality Synapse reman avoids the cost and downtime of swapping an entire turbocharger assembly, while still resolving electronic boost control faults.
The reman actuator is a fraction of the price of a new OE turbo assembly, making it an attractive option for out‑of‑warranty trucks or fleet vehicles.
Remanufactured in a dedicated U.S. facility focused on circuit board and electronic module rebuilding, ensuring tight process control and repeatable quality.
Synapse reman actuators have an emphasis on quality and fixing root causes, not just clearing codes.
Application: 2017–2019 Chevrolet and GMC 6.6L Duramax (L5P).
Condition: Remanufactured actuator, sold as Remanufactured in terms of function and warranty.
OEM cross‑reference: 12723306, 12708802.
Approximate weight: 2.5 lb; typical package dimensions around 5 x 10 x 12 in for shipping.
Brand: Synapse
NorCal Diesel Performance sells this Synapse reman actuator with a warranty honored by the manufacturer.
Term: 1‑year warranty from the original date of purchase.
Coverage: If the actuator fails due to internal component failure or workmanship within the warranty period, the unit will be repaired again or replaced at no additional charge, or the cost of the repair may be refunded at the remanufacturer’s discretion.
Non‑transferable: Coverage applies only to the original purchaser and the original vehicle installation and does not transfer if the vehicle or part is sold.
Scope limits: The warranty covers the actuator itself, not related vehicle systems; it does not cover towing, rental, lost time, or consequential damage.
Exclusions: Failures traced to external causes—such as wiring issues, incorrect installation, contamination, or other failed components—are not covered and may void warranty claims.
Because L5P turbo actuators must be calibrated after installation, proof of proper calibration and installation may be requested as part of any warranty evaluation.
When this actuator is sold on an exchange basis, the core policy is as follows.
Core return required: A serviceable L5P turbo actuator core must be returned after installation of the reman unit.
Core Charge: Core charge will be applied up front at checkout and is fully refundable as long as the following conditions are met.
Time frame: Cores must be received within about 15 days from the ship date of the exchange, after 15 days core acceptance is up to the manufacturer.
Core condition requirements:
Must be an L5P turbo actuator (correct application).
No fire or flood damage.
Circuit board and housing must be complete with all original components.
Prior repair attempts are acceptable as long as the housing and board are intact.
Customers should always follow NorCal Diesel Performance’s specific core instructions and contact us with any questions.
A failing L5P turbo actuator can mimic turbocharger or drivetrain issues. The following symptoms commonly point back to the actuator or its circuit on 2017–2019 L5P trucks.
“Reduced Engine Power” or similar limp‑mode messages, often appearing under load or during acceleration, sometimes clearing with a key cycle.
Noticeable loss of power, especially at low to mid RPMs, with delayed or uneven turbo spool‑up.
Turbo feels like it is “on and off” or will not respond smoothly, causing inconsistent acceleration or towing performance.
Common DTCs associated with L5P turbo actuator faults include:
P003A – Turbocharger/Supercharger Boost Control A Position Not Learned / control position exceeded learning limit.
P0046 – Turbocharger/Supercharger Boost Control A Range/Performance.
P2562 / P2563 – Turbocharger Boost Control Position Sensor or Vane Position Actuator range/performance (seen on other Duramax generations but similar in nature).
Underboost codes such as P0299 can also appear when the actuator fails to position the vanes correctly, though these may also indicate other boost system issues.
An actuator‑related problem is more likely when codes can be temporarily cleared, performance returns after a restart, and there is no excessive turbo noise or smoke.
Intermittent limp mode that resets after cycling the ignition, especially with P003A/P0046 stored.
Vane position data on a scan tool that fails to follow commanded position or seems stuck, even though the turbocharger bearings themselves are quiet and there is no siren‑like whine.
No major oil consumption, blue/gray smoke, or metallic turbo noises, which would instead point to a failing turbocharger rather than the actuator.
If any of these symptoms match what the truck is doing and mechanical turbo health has been verified, replacing the actuator with a properly remanufactured and calibrated Synapse unit is often the most direct fix.
Before condemning the actuator, technicians and advanced DIY owners commonly follow these checks:
Scan for codes and freeze‑frame data to confirm P003A, P0046, or related vane position faults and note the conditions under which they set.
Inspect the actuator wiring harness and connector for corrosion, bent pins, or chafed wiring that could cause intermittent communication or position errors.
Command vane position with a scan tool (if supported) and watch for the actuator to respond smoothly; lack of movement or erratic behavior indicates an actuator or turbo unison ring issue.
Verify there are no major exhaust leaks before the turbo, or severe boost leaks in charge pipes/intercooler, which can mimic actuator underboost symptoms.
Evaluate turbo mechanical condition—shaft play, wheel damage, and oil leakage—to differentiate between actuator failure and actual turbocharger failure.
When diagnostics confirm an electronic control or position feedback problem at the actuator, swapping in this Synapse reman unit is the recommended repair path.
This section provides high‑level expectations for the installer; always follow vehicle‑specific procedures and safety steps.
Physical installation: The actuator is mounted on the turbocharger with several fasteners and a keyed engagement to the vane linkage; access is tight near the Y‑bridge but manageable with basic hand tools and patience.
Electrical connection: The actuator plugs into the existing harness with an OE‑style connector; ensure the connector is clean, fully seated, and properly latched.
Calibration required: After installation, the L5P actuator must be calibrated on the truck using appropriate scan‑tool procedures so the ECM can learn the vane sweep and position limits.
Best practice: Clear all related codes, perform the calibration routine, and complete a road test under varied load to confirm the turbo responds smoothly and no codes return.
Improper installation alignment or skipped calibration can lead to recurring P003A/P0046 codes even with a good actuator, so professional installation or careful adherence to service information is strongly recommended.
The Synapse L5P actuator comes pre‑programmed for the L5P application and bolts directly in place, but the truck still requires a post‑install calibration or “learn” procedure through a suitable scan tool. Without this calibration, the ECM may set P003A or similar “position not learned” codes even with a new unit.
If diagnostics confirm that the actuator and its circuit are the root cause—rather than a sticking turbo unison ring, wiring issue, or boost leak—replacing the actuator with this remanufactured unit is specifically intended to resolve P003A and P0046 codes along with associated performance complaints. Additional mechanical turbo faults or wiring problems must be addressed separately.
Actuator issues tend to cause intermittent limp mode, underboost codes, and performance that temporarily returns after a key cycle, often without excessive turbo noise or smoke. Turbocharger failures typically produce loud siren‑like whine, blue or gray smoke, oil in the intercooler, and severe power loss that does not improve with a restart. A technician can confirm by checking vane movement, actuator response, and mechanical turbo condition.
This is a professionally remanufactured Synapse turbo actuator that has been completely rebuilt and pre‑programmed, then tested on an actual turbocharger to verify proper function. It is sold in “Remanufactured” condition with a 1‑year warranty.
This L5P actuator is sold as an exchange unit that requires return of your original L5P actuator core; a core charge is applied at checkout and refunded once the core is returned. Core units must be complete, free of fire or flood damage, and must be genuine L5P actuators. Damaged, incomplete or non-genuine actuators may reduce or forfeit core value.
The 1‑year warranty is backed by the remanufacturer Synapse and administered through them directly, following coverage principles as the L5P actuator program. Warranty coverage applies only to the actuator itself and excludes labor, towing, and other incidental costs. Visit https://synapseauto.com for more information.
The actuator is designed to meet or exceed factory performance for stock‑calibrated L5P trucks and will physically function on tuned vehicles, but aggressive or improper tuning that alters vane control strategies can shorten actuator and turbo life. Failures caused by tuning, wiring changes, or non‑OE modifications may not be covered under warranty, so customers should consult their tuner and review warranty terms carefully.
The actuator itself is an OEM‑equivalent replacement electronic component that does not alter emissions hardware or calibration and is generally treated as a repair part for the existing turbo system. Users are still responsible for maintaining all factory emissions controls and complying with federal, state, and local regulations.
Experienced DIY owners with good mechanical skills and the right tools can physically replace the actuator, though access around the turbo and Y‑bridge is tight, and care must be taken to align the actuator properly on the vane linkage. Because a calibration routine is required to complete the repair, most owners will either need access to a capable scan tool or should plan on having a shop perform the final calibration and verification.
When servicing an L5P turbo actuator, it is good practice to:
Inspect and clean the electrical connector and harness routing to the actuator.
Check for exhaust leaks before the turbo and boost leaks in charge pipes and intercooler.
Evaluate the turbo for abnormal shaft play, wheel damage, or heavy oil leakage.
Confirm there are no unrelated codes (fuel system, MAP, MAF, etc.) that could influence boost control.
Addressing these items at the same time as the actuator replacement increases reliability and reduces the chance of repeat turbo‑related faults.
This Synapse remanufactured L5P turbo actuator gives NorCal Diesel Performance customers a focused, cost‑effective solution for common 2017–2019 Duramax turbo control failures, backed by a 1‑year warranty and professional remanufacturing quality.
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