Self-Diagnostic System: Notes

ECM monitors performance of engine for misfires, catalyst efficiency, exhaust leaks and evaporative control loss. If a fault occurs, the ECM stores a relevant fault code and notifies driver of component failure by illuminating Malfunction Indicator Light (MIL) located in instrument cluster. On vehicles equipped with A/T, ECM combines with Electronic Automatic Transmission (EAT) ECU to provide an OBD/powertrain operating strategy. If ECM detects a fault during its engine operation, it will be caused by one of the following:

• Minimum value of a component signal has been exceeded.
• Maximum value of a component signal has been exceeded.
• Component signal is not present or has not been detected.
• An improbable condition has been diagnosed.

By analyzing various input signals system sensors, ECM detects system failures related to ignition, fueling or exhaust systems. ECM stores Diagnostic Trouble Codes (DTCs) associated with a detected failure until diagnostic system is cleared. A 16-pin Data Link Connector (DLC) is used for vehicle diagnostics. On Discovery models, DLC is located under steering wheel. On Range Rover models, DLC is located in front passenger footwell. When a relevant fault is detected, the fault condition is stored in the ECM memory.