Service Precautions

Before proceeding with system diagnosis, following precautions must be followed:

• Ensure fuel pressure is released before removing fuel line or fittings, as fuel system is under pressure and may cause personal injury.
• When using SELF-DIAGNOSTIC TESTS for diagnosis, DO NOT skip any steps, or incorrect diagnosis may result. When instructed to disconnect any connector, check that the connector is clean and in good condition after disconnecting the connector. Repair or clean connector if necessary. Always perform indicated verification procedure after repairs are made. Verification tests are listed at the end of the self-diagnostic tests.
• When using a jumper wire, ensure either jumper wire or circuit is fuse-protected.
• Before disconnecting connector at any control module, ensure ignition is off before removing connector.
• When checking voltage or continuity at any control module, probe connector for control module from pin side. DO NOT backprobe connector unless instructed too in test procedure. DO NOT probe wires through the insulation.
• DO NOT cause short circuits when performing electrical tests. This will set additional Diagnostic Trouble Codes (DTCs), making diagnosis of original problem more difficult.
• Use specified test equipment when performing electrical tests.
• When checking for spark, ensure no fuel leaks exist and spark plug wire or coil wire is NOT more than 1/4" from engine ground. If coil wire is more than 1/4" from engine ground, damage to vehicle electronics and/or PCM may result.
• DO NOT prolong testing of injectors or engine may hydrostatically lock.
• If replacing Powertrain Control Module (PCM), the correct vehicle mileage and Vehicle Identification Number (VIN) must be programmed into the PCM to prevent Diagnostic Trouble Codes (DTCs) to be set in the Anti-Lock Brake System (ABS) module and Supplemental Restraint System (SRS) module. See POWERTRAIN CONTROL MODULE PROGRAMMING  under POWERTRAIN CONTROL MODULE.