Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

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Testing Precautions

The following items must be checked and precautions taken when performing any electronic engine control testing procedures.

1. Ensure battery is known good and fully charged.
2. Ensure engine is mechanically sound and operating temperature is proper.
3. Ensure wiring harness connections are clean an tight.
4. Use caution never to touch ignition high voltage primary or secondary terminals.
5. Disconnect main relay prior to checking engine compression.
6. To prevent ignition coil and ECU damage, never directly ground ignition coil.
7. Ensure battery cable clamps are tight prior to starting engine.
8. Never crank engine with high tension wire disconnected from coil, or disconnect coil wire or battery cables with engine running.
9. Always disconnect battery cables prior to charging the battery.
10. If using an electric welder or placing vehicle in a paint oven the ECU must be removed from vehicle.