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. See FUEL PRESSURE RELEASE  procedure.
• When performing self-diagnostic tests, DO NOT  skip any steps, or incorrect diagnosis may result. Always perform indicated verification procedure after each repair.
• When using a jumper wire, ensure either jumper wire or circuit is fuse-protected.
• Before disconnecting connector from any control module, ensure ignition is off before removing connector.
• When checking voltage or continuity at any control module, DO NOT backprobe connector (unless instructed to do otherwise in test procedure), or probe wires through the insulation.
• DO NOT  cause short circuits when performing electrical tests. This will set additional DTCs, making diagnosis of original problem more difficult.
• Use test equipment specified in test procedures when performing electrical tests.
• When checking for spark, ensure cable is NOT more than 1/4" from engine ground. If cable is more than 1/4" from engine ground, damage to vehicle electronics and/or PCM may result.
• DO NOT  prolong testing of fuel injectors or engine may hydrostatically lock.