Service Precautions

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

• Before performing any testing procedures, check for any related Technical Service Bulletins (TSB).
• Ensure fuel pressure is released before removing fuel line 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. Verification tests are listed under VERIFICATION TESTS  .
• DO NOT use 12-volt test light when checking 5-volt supply circuit, PCI or SCI bus circuit, camshaft position sensor signal circuit, crankshaft position sensor signal circuit, Oxygen (O2) sensor signal circuit or vehicle speed sensor signal circuit or O2 sensor circuit, Powertrain Control Module (PCM) may be damaged.
• When using a jumper wire, ensure either jumper wire or circuit is fuse-protected.
• Ensure ignition is off before disconnecting connector from any control module.
• DO NOT probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal-to-pin connection. Install Miller Special Tool (8815) to perform diagnosis.
• When checking voltage or continuity at any control module, use the terminal side (not the wire end) of the connector. DO NOT probe wire through insulation or backprobe connector (unless instructed to do otherwise in test procedure).
• DO NOT cause short circuits when performing electrical tests. This may cause additional Diagnostic Trouble Codes (DTC) to be set, making diagnosis of original problem more difficult.
• Use specified test equipment when performing electrical tests.
• DO NOT prolong testing of fuel injectors or engine may hydrostatically lock.
• If replacing PCM, the correct vehicle mileage and Vehicle Identification Number (VIN) must be programmed into the PCM to prevent DTCs from being set in Controller Anti-Lock Brake (CAB) and Supplemental Restraint System (SRS) Air Bag Control Module (ACM). See POWERTRAIN CONTROL MODULE  under PROGRAMMING.
• If replacing PCM on models with a Sentry Key Immobilizer Module (SKIM), secret key data must be updated to enable engine starting. To update secret key data, see SENTRY KEY IMMOBILIZER MODULE  under PROGRAMMING.