Computers and Control Systems: Service Precautions

1. Do not run the engine if the battery terminals are not properly tightened.
2. Never disconnect the battery while the engine is running.
3. Disconnect the battery from the car when charging.
4. Never use an auxiliary starting assist device rated above 12 volts to start the engine.
5. Always turn the ignition off before connecting or disconnecting plugs on sensors, the ECU, or any ECU controlled devices to avoid any voltage spikes to the ECU.
6. Prior to disconnecting lines or hoses from fuel system components, relieve residual system pressure to prevent fuel from spraying from connections.
7. Before reconnecting an electrical connector, check:
a. The condition of the terminals (shape, condition, oxidation, etc.).
b. The positive locking of the terminals inside their connectors.
c. The condition of the rubber seal or boot (if used).
d. That the locking spring is in good condition.
8. If any electrical welding is to be done, disconnect the battery, climate control, injection, and cruise control ECU's, the radio, and any other device that might have I.C. controls.
9. If the vehicle is to be exposed to temperatures above 80°C (176°F) (such as an infra-red paint booth) remove any I.C. controlled devices (ECU, climate control computer, etc.).
10. When taking a compression test, remove the fuel pump relay to avoid feeding fuel to the injectors.
11. Do not use a self powered test light to test the continuity of a circuit (the voltage may damage electrical components).
12. Do not create any arcing to check for power in a circuit.
13. On vehicles equipped with a catalytic converter:
a. Use only 'UNLEADED FUEL".
b. Avoid running out of fuel.
c. If running tests on a dynamometer, make sure the catalytic converter is well ventilated.