Malfunction Indicator Lamp: Service and Repair

1987-88 Models Less Turbo Engine
The check engine lamp will be illuminated when the ignition switch is in the On position with engine not operating. When engine is started, the Check Engine lamp should go off. If lamp remains on, a code has been stored by the Electronic Control Module (ECM) memory. After diagnosis and repair, with diagnosis switch in Off position, start engine and allow to reach operating temperature. After engine has reached operating temperature, the Check Engine lamp should be off while engine is operating.

1987-88 Models w/Turbo Engine
The check engine lamp will be illuminated when the ignition switch is in the On position with engine not operating. When engine is started, the Check Engine lamp should go off. If lamp remains on, a code has been stored by the Electronic Control Module (ECM) memory. After diagnosis and repair, place ignition switch in Off position, then clear codes stored in the ECM memory by disconnecting the battery ground cable, for approximately 20 seconds.