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.
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HOMESERVICE MANUALSJEEP1986CHEROKEE LAREDO, 2D UTILITY, 2.1 B, 4WDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEM2.8L FEEDBACK CARBURETOR SYSTEMOPERATIONELECTRONIC CONTROL MODULE (ECM)MEMORIES
1986 Jeep Cherokee Laredo, 2D Utility, 2.1 B, 4WD
Electronic Control Module (ECM): Memories
1986 Jeep Cherokee Laredo, 2D Utility, 2.1 B, 4WDSECTION Memories
The 3 types of memories in the ECM are: Read Only Memory (ROM), Random Access Memory (RAM), and Programmable Read Only Memory (PROM).
- Read Only Memory (ROM) - The ROM is preprogrammed information that can only be read by the ECM. The ROM program cannot be changed. If battery voltage is removed, ROM information will be retained.
- Random Access Memory (RAM) - This memory is the decision making center for the CPU. It works like a calculator. Data sensor input, diagnostic codes and results of calculations are temporarily stored in the RAM memory. If battery voltage is removed from the ECM, all information stored in this memory is lost.
- Programmable Read Only Memory (PROM) - This memory is factory programmed information, including engine calibration data, transmission, vehicle weight, and rear axle ratio application. The PROM can be removed from the ECM. If battery voltage is removed, PROM information will be retained.
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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.