On-Board Diagnostics

When an abnormality occurs in a signal from a sensor, or when a problem occurs in one of the systems monitored by the Electronic Control Unit (ECM), the ECM lights the Check Engine light and stores the Diagnostic Trouble Code (DTC) in erasable memory. When the ignition is initially turned on, the ECM lights the Check Engine light for two seconds to test the bulb. The ECM is located under bulkhead panels, behind the passenger seat. See Figure .