Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Engine Identification Number Locations: 4.0L
For both the Grand Cherokee and Wrangler, the engine build date code is located on a machined surface on the right side of the cylinder block. See Fig 1 . The digits of the code identify the following.
- 1st digit identifies the year (3 = 2003).
- 2nd and 3rd digits identify the month. Example; (01 - 12).
- 4th and 5th digits identify the engine type/fuel system/compression ratio. HX = 2.5L (150 CID) 9.1:1 compression ratio engine with a multipoint fuel injection system. MX = 4.0L (242 CID) engine with multipoint fuel injection system.
- 6th and 7th digits identify the day of engine build. Example; (01 - 31).
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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