Service Precautions

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

• Ensure fuel pressure is released before disconnecting fuel lines or fittings, as fuel system is under pressure and may cause personal injury. See FUEL SYSTEM PRESSURE RELEASE  .
• When using 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.
• DO NOT use 12-volt test light when checking 5-volt or 8-volt supply circuit, bus circuits, camshaft position sensor signal circuit, crankshaft position sensor signal circuit, oxygen sensor signal circuit or vehicle speed sensor signal circuit or Powertrain Control Module (PCM) may be damaged.
• 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, probe connector for control module from pin side. DO NOT backprobe connector or probe wires through the insulation unless specifically directed to do so.
• DO NOT cause short circuits when performing electrical tests. This will set additional Diagnostic Trouble Codes (DTC), making diagnosis of original problem more difficult.
• Use specified test equipment when performing electrical tests.