Electronic Control Module (ECM)

The ECM constantly examines input information from various sensors to configure output signals to fuel and ignition system components. ECM monitors sensor input signals and diagnoses out-of-range signals.

A faulty signal causes ECM to switch on Service Engine Soon light. Faulty signal records are stored in ECM memory and can be accessed in the form of a signal code. Stored fault code output may be requested by jumping a circuit of ALDL connector. Codes are read by counting Service Engine Soon light flashes or with a Scan tester.

The ECM is similar to one used in various General Motors vehicles. To adapt it to specific applications, each ECM is fitted with a replaceable Memory Calibration (MEM-CAL) chip. See Fig 1 . Manufacturers may update MEM-CAL chips to repair driveability problems. Replacement ECM's often are delivered without MEM-CAL chip installed.

Fig 1: ECM & MEM-CAL Location & Mounting

Courtesy of GENERAL MOTORS CORP.

NOTE: Components are grouped into 2 categories. The first category covers INPUT DEVICES, which control or produce voltage signals monitored by the ECM. The second category covers OUTPUT SIGNALS, which are components controlled by the ECM.