Spectrum L4-91.5 1.5L (1989)
Engine Control Module: Description and Operation
ECM Location
The Electronic Control Module (ECM), located above the passenger kick pad, is the control center of the feedback M/C carburetor system. It constantly
looks at the information from various sensors, and controls the systems that affect vehicle performance. The ECM performs the diagnostic function of the
system. It can recognize operational problems, alert the driver through the "CHECK ENGINE" light, and store a code or codes which identify the
problem areas to aid the technician in making repairs.
PROM (Programmable Read Only Memory)
To allow one model of ECM to be used for many different cars, a device called a PROM is used. The PROM is located inside the ECM, and contains
program information tailored to the vehicle's weight, engine, transmission, axle ratio, and several other factors. While one ECM part number can be used
by many car lines, a PROM is very specific and must be used for the right car. For this reason, it is very important to check the latest parts book and
Service Bulletin information for the correct part number when replacing a PROM.
