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LS tuning glossary

Plain-English definitions for the terms you'll run into.

24x / 58x
24x (Gen III: LS1, LS6, LQ4, LQ9, Vortec trucks through 2006) uses a 1x cam sensor; 58x (Gen IV: LS3, LS7, L76, L92, 2007+ Vortec trucks, 2007+ LS2) uses a 4x cam sensor. Exception: 2005–06 LS2s are 24x, so they need a 24x harness and computer. PCM, harness and sensors must match; a Gen III PCM on a 58x engine needs a conversion box. More →
AFM / DOD
AFM (introduced 2005 in Tahoe-class SUVs) deactivates both valves on four cylinders using oil-pressure-controlled lifters fed by the LOMA/VLOM valley-cover manifold. More →
Drive-by-wire (DBW)
Drive-by-cable: throttle opened mechanically (early Gen III trucks, Camaro LS1). Drive-by-wire: PCM opens the throttle from a pedal-position sensor (all Gen IV). A DBW swap needs the pedal wired and calibrated. (PSI also says "most LS1/LS6" are DBW; C5 Corvette LS1 was DBW while F-body LS1 was cable; treat per-application) More →
PCM / ECM
The PCM reads crank, cam, MAF, coolant, IAT and O2 sensors to control fuel, spark and idle (and shifts on automatics); on drive-by-wire engines it also controls the throttle. More →
Standalone harness
A standalone harness keeps only the circuits the engine needs to run, removing body-specific donor wiring. More →
VATS
GM's anti-theft system. In a swap, it has to be deleted in the tune or the engine won't start. More →
Stall speed
How far the engine can rev with the brakes locked and the transmission in gear before the wheels turn; it rates a torque converter. More →
Line pressure
The transmission's hydraulic pressure. On a 4L60E the computer controls it, along with shift timing. More →
TV cable vs kickdown cable
A kickdown cable just forces a downshift at wide-open throttle. A TV (throttle valve) cable, used on transmissions like the 700R4, controls shifting and must be adjusted precisely. More →
Torque model
Part of the factory calibration that an aftermarket cam requires changing, along with idle, fuel and spark. More →
Self-learning EFI
Standalone systems that adjust fuel and timing from real-world driving, like Holley's Terminator X. More →

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Sources
  1. 4L60 Transmission Complete Guide | Diagrams, HP Ratings, Swap FAQ — Speedway Motors
  2. Ask Away! How to Delete the AFM System in a 5.3L LS Truck Engine (Jeff Smith) — OnAllCylinders (Summit Racing)
  3. DOD, AFM, And DFM Deletes: A Q&A With Michigan Motorsports — LSX Magazine
  4. What Every LS Swap Builder Needs to Know About the PCM and Harness — PSI Conversion
  5. The Complete LS Swap Wiring Harness Buyer's Guide — PSI Conversion
  6. EFI vs Carb: Is Converting Carb to EFI Worth It? Pros and Cons — Speedway Motors
  7. How to Choose a Torque Converter — Speedway Motors
  8. Carbureted LS Engine Guide How to Carb an LS | Build Recipe — Speedway Motors
  9. How To Adjust, Install & Troubleshoot Throttle Cable & Kickdown Cables — Speedway Motors