Replaces Ford OEM 3C3Z-12B637-AB (Discontinued)
If you're restoring or repairing an early-build 2003 6.0L Power Stroke, finding a quality engine wiring harness has become increasingly difficult. Ford discontinued OEM part number 3C3Z-12B637-AB, leaving many truck owners searching for an affordable and dependable replacement. This aftermarket engine wiring harness is manufactured as a direct replacement, restoring factory electrical connections without the cost or scarcity of obsolete OEM parts. Ford lists the original harness as discontinued, and it was designed for engines built before January 30, 2003, with the injector harness integrated into the main engine harness.
Manufactured to meet or exceed OEM specifications, this harness features factory-style connectors, proper wire routing, and OEM-style terminals to ensure dependable communication between the PCM, FICM, injectors, sensors, glow plug system, and engine-mounted electrical components.
Whether you're replacing a melted harness, repairing years of wiring damage, or completing a full engine rebuild, this harness provides a direct-fit solution for early 6.0L Power Stroke applications.
Features
- Direct replacement for Ford OEM 3C3Z-12B637-AB
- Designed for Early 2003 6.0L Power Stroke
- Fits engines built before January 30, 2003
- Correct integrated injector wiring harness (early production design)
- OEM-style connectors and terminals
- High-temperature wire insulation
- Factory-style routing for proper installation
- Plug-and-play replacement
- Brand new aftermarket replacement
- Excellent choice when original Ford harness is discontinued
Replaces OEM Part Numbers
- 3C3Z-12B637-AB
- 3C3Z12B637AB
Replaces Navistar / International Numbers
- 1847045C91
- 1844385C91
- 1843476C91
This harness ONLY fits early-production 2003 6.0L Power Stroke engines built BEFORE January 30, 2003.
Early production engines use an integrated injector wiring harness as part of the main engine harness. Trucks built after January 30, 2003 use a different engine harness (3C3Z-12B637-BA) with a separate injector harness and are not interchangeable.
If you are unsure which harness your truck requires, verify your engine build date or VIN before ordering.
Common Symptoms of a Failed Engine Harness
- Intermittent injector misfires
- Injector circuit diagnostic trouble codes
- No-start condition
- FICM communication faults
- ICP sensor circuit faults
- IPR circuit faults
- Camshaft or crankshaft sensor codes
- Glow plug circuit issues
- Chafed, melted, or oil-contaminated wiring
- Electrical shorts caused by heat or age
Replacing a damaged engine harness can eliminate intermittent electrical issues that are often mistaken for failed injectors, a bad FICM, or sensor failures.
***Does not include the injector harness / Injector harness sold separately***
