Computers and Control Systems: Service Precautions

1. Do not run the engine if the battery terminals are not properly tightened.
2. Do not disconnect the battery while the engine is running.
3. Disconnect the battery while it is being recharged.
4. Never use an auxiliary starting-assist device which has a voltage rating above 12 volts to start the engine.
5. Do not disconnect the ECU while the ignition circuit is live.
6. Before reconnecting a connector, check:

a. The condition of the terminals (shape, condition, oxidation).
b. The positive locking of the terminals inside their connectors.
c. That the rubber seal or boot is present (if used) for watertightness and locking.
d. That the locking spring is in good condition and operating.

7. In cases of electrical welding (for instance, spot welding), disconnect the climate control, injection, and cruise control ECUs and the radio.
8. In cases of temperatures above 80° C (176° F) (example: infra-red spray booth), remove all ECU's.
9. When taking a compression test, remove the fuel pump relay. (This will prevent feeding fuel to the injectors).
10. Do not use a test light to check a circuit for continuity.
11. Do not create any arcing to check the continuity of a circuit.
12. On vehicles equipped with catalytic converters, the following conditions must be observed:

a. Use only "UNLEADED FUEL".
b. Avoid running out of fuel.
c. In case of poor engine operation (misfiring), avoid driving the vehicle and have the problem corrected as soon as possible.
d. Do not disconnect a spark plug wire with the engine running.
e. Avoid push starting the vehicle.
f. If running tests on a Dynamometer, make sure the catalytic converter is well ventilated.