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2003-2006 GM Gen III 4.8/5.3/6.0L EFI Harness - Throttle by Wire By Painless Performance
Made In USA
P/N 60221 $715.99
2003-2006 GM Gen III 4.8/5.3/6.0L EFI Harness - Throttle by Wire



Check Quality Tested - Lifetime Warranty
Check All New Connectors/Terminals
Check High Quality TXL Wire
Check OBD-II Port included
Check Check Engine Light included

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  • App
  • Specs

This harness is standalone and is not intended to replace the OEM engine wiring.  Standalone harnesses are intended to run the designated engine & transmission only, generally when swapped into another vehicle.  

Painless LS swap wiring harnesses make getting your engine swap wired a simple task!

This harness is designed for use on the 2003-2006 4.8L, 5.3L, 6.0L throttle by wire engines with  a 4L60E, 4L65E, 4L70E, 4L80E, 4L85E, or manual transmission. These engines were found in factory 2003-2006 Vortec Trucks.  Engine codes supported are LR4, LM7, LM4, LQ4 and LQ9. This harness will support flex fuel and non flex fuel engines. Flex fuel engines will require an inline fuel composition sensor in order to run E85 fuel. Included with this harness is a 10 circuit weatherproof fuse block & mounting bracket and GM color coded wires with labels for easy installation. 

This standard length harness allows four feet from the back of the intake manifold to where the fuseblock and ECM mount.  Perfect for those that plan to mount these components under the dash or in the glove box.

This kit includes:

  1. All new fuel injection harness with OEM fitment connectors and harness breakouts
  2. OBDII connector, mounting bracket and check engine light
  3. Crimp-on terminals, rubber grommet
  4. Mounting hardware

This harness will not work with 2006 accelerator pedals and ships with conenctors for 2003-2005 5.3L oxygen sensors.  We recommend checking the online manual for the full list of required mating parts prior to ordering.





WarningProp 65 Warning
Hazardous Material Warning

WARNING: This product can expose you to chemicals including lead which is known to the State of California to cause cancer or birth defects or other reproductive harm. For more information, visit

Link to P/N:
Engine: 4.8L, 5.3L, 6.0L w/ Throttle By Wire
Trans.: 4L60E, 4L65E, 4L70E, 4L80E, 4L85E, or manual

Number of Circuits: 10 Fuses with 2 Ignition, 1 Cooling Fan & 1 Fuel Pump Relay
Harness Length: 4 Feet Between Engine and ECM
Fuse Type: Mini Blade
Firewall Passthrough: Grommet
Color Code Based:  1999 - 2006 C/K Truck
Circuit Designations: Printed Wire Tags on all Connectors and Open Ended Wires

The Fuse Block Protects The Following Circuits:

  • Brake and Cruise Switch
  • Dual 40 amp Ignition Relays
  • ECM (IGN)
  • ECM B+
  • Fuel Injectors
  • Fuel Pump
  • Heated O2 Sensors
  • Ignition Coils
  • Mass Airflow and Fuel Compensation Sensor
  • Throttle Actuator Control Module 
  • Transmission and Park Neutral Position Switch
  • 20 Amp Cooling Fan Relay
  • 20 Amp Fuel Pump Relay


This harness includes connections for the following components:

  • A/C Request
  • Accelerator Pedal Position Sensor
  • Alternator 
  • Brake Switch
  • Cam Position Sensor
  • Cooling Fans
  • Crank Position Sensor
  • Cruise Control
  • Data Link Connector 
  • Driver/Pass Front O2 Sensors
  • ECM
  • Engine Coolant Temperature
  • Fuel Compensation Sensor
  • Fuel Pump
  • Fuel Pump Test 
  • Grounds 
  • Ignition Coils
  • Ignition Switch Signal
  • Injectors - Gas & Flex Fuel Sub-Harness
  • Input Speed Sensor
  • Knock Sensors
  • Malfunction Indicator Lamp
  • MAP Sensor
  • Mass Airflow / Intake Air Temperature Sensor
  • Output Speed Sensor
  • Park/Neutral Switch
  • Reverse Lights
  • Starter
  • Starter Relay Activation
  • Tachometer
  • Throttle Actuator Control Module 
  • Throttle Actuator Control Module to Accelerator Pedal Pigtail
  • Throttle Body 
  • Transmission
  • VSS Output for Speedometer
  • Knock Sensor Pigtail