Self-Diagnostic System: Notes

When systems related to the emission controls malfunction during normal operation, a related trouble code will be stored in ECM memory. On California models without ECM "D" mark, if trouble occurs in idle switch circuit, ECM will not activate CHECK ENGINE light. If troubled circuit regains good condition, memory of defective area will be erased automatically.

• California  When a system fault occurs, CHECK ENGINE light on dash will illuminate to inform driver a problem exists. Light will remain on until fault goes away or system is serviced. Stored codes may later be accessed and identified by counting flashes of the CHECK ENGINE light. If fault goes away (system parameter returns to normal operation) before vehicle is serviced, CHECK ENGINE light will go out. Related fault code will still remain in ECM memory until cleared. If ECM memory is not cleared, ECM memory will automatically be erased after 50 engine starts.
• Federal & Canadian (ECM Without "D" Mark)  When a system fault occurs, CHECK ENGINE light on dash will illuminate to inform driver a problem exists. When a fault occurs, ECM stores trouble code in memory. Memory is not erased even when ignition is turned off. Memory is retained until normal signal is inputted to ECM or power to ECM is shut off for 20 seconds or longer. Stored codes may later be accessed and identified by counting flashes of CHECK ENGINE light.
• Federal & Canadian (ECM With "D" Mark)  System functions same as California models except on ECM's with "D" mark. On ECM's with "D" mark, if a fault occurs in lock-up circuit or gear position switch, ECM will not indicate it or activate CHECK ENGINE light. When troubled circuit regains good condition, memory of defective area will be erased automatically.