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#425550603
Holley 550-603 HP EFI ECU & Harness Kit, LS2/LS3/LS7, Bosch O2
$2,446.95
/each
Factory Shipped
$2,719.95
Save $273.00
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Product Summary
Universal Fit, 58x Crank Reluctor, 4x Cam Trigger
Rebates Available
See rebate detailsKey Specs
| MFG. Part # | 550-603 |
| Brand | Holley |
| Ignition Type | Factory GM |
| Tuner Style | USB/CAN Tuning Cable |
Need To Know
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Holley 550-603 Details
Looking for a plug and play kit for your GM LS engine? The HP ECU allows you to accurately control the fuel and ignition of your engine plus much more. Got a stock LS engine? Simply download a base map and you're on your way. Got a turbocharged, nitrous fed LS engine on water/meth? This HP EFI kit can control that too!
- Simple Installation - Plug and Play control of GM LS2/LS3/LS7 engines. Just plug the harness into your factory sensors, wire the power and grounds and you are ready to take complete control of your LS engine
- More Functionality - Provides significantly more functionality than OEM or other competitive ECUs (boost control, nitrous control, water/meth injection, plus a host of additional inputs and outputs to control fans, pumps, relays etc.)
- Easy To Use - Laptop programmable ECU includes a variety of base maps that will have you hitting the cruise or track in no time
- Ideal For Everything - including stock 5.3L engine swaps or all out, 3,000 horsepower race cars that need a simple and powerful ECU and harness solution
- Industry Leading Self Tuning Fuel Strategy - means less time tuning and more time enjoying the power of your LS vehicle
- Kit includes ECU, harness, communication cable, software, USCAR (EV6 Style) injector connectors, and Bosch wideband O2 sensor, designed to be used with GM LS2/LS3/LS7 engines with factory GM coils and a 58 tooth crank sensor
- ECU is fully potted and can be mounted in the engine compartment or interior
- Sealed automotive and marine grade connectors
- 1-5 Bar MAP sensor capability
- Optional plug and play hand-held programmer, 5.7" touch screen and digital gauges are available for ultimate control and vehicle monitoring
- ECU is certified to ISO 8846, SAE J1171 & United States Coast Guard Requirements for Ignition Protection & Fire Resistance
- For a full list of advanced features such as boost, nitrous, water/meth, individual cylinder control and more click the document icon under the product image!
Charts
Rebates
Holley IRS Sale 2026
Save 10% instantly on select products across the Holley family of performance brands during the annual Holley I.R.S.Tax Sale. Instant rebate period runs from February 17, 2026 through March 29, 2026.
Guides & Documents
CARB Warning
For race/ off road use only
CARB Warning
For race/ off road use only
Holley 550-603 Specifications
Holley 550-603 Specifications
| KEY SPECS | |
|---|---|
| MFG. Part # | 550-603 |
| Brand | Holley |
| Ignition Type | Factory GM |
| Tuner Style | USB/CAN Tuning Cable |
| GENERAL | |
| Crank Reluctor | 58x |
| Cam Trigger | 4x |
| Injector Connector | USCAR (EV6) |
| MAP Sensor Included | No |
| Transmission Control | No |
| Oxygen Sensor Style | Bosch |
| GTIN Code | 090127666937 |
| Sold in Quantity | Kit |