Service Precautions

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

• Engines produce carbon monoxide that is odorless, causes slower reaction time, and can lead to serious injury. When the engine is operating, keep service areas well ventilated or attach the vehicle exhaust system to the shop exhaust removal system.
• Set the parking brake and block the wheels before testing or repairing the vehicle. It is especially important to block the wheels on front-wheel drive vehicles; the parking brake does not hold the drive wheels.
• When servicing a vehicle, always wear eye protection, and remove any metal jewelry such as watchbands or bracelets that might make an inadvertent electrical contact.
• Before performing any testing procedures, check for any related technical service bulletins.
• 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 connector. Repair or clean connector if necessary. Always perform indicated verification test after repairs are made.
• When using a jumper wire, ensure either jumper wire or circuit is fuse-protected.
• Before disconnecting any control module harness connector, ensure ignition is off before removing connector.
• DO NOT use 12-volt test light when checking 5-volt or 8-volt supply circuit, bus circuits, PCI bus circuit, 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 checking voltage or continuity at any control module, probe control module harness connector from pin side. DO NOT backprobe harness connector unless instructed to 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 (DTC), 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.
• When replacing Transmission Control Module (TCM), pinion factor and shift quality quick learn procedure should be performed. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION.
• If Powertrain Control Module (PCM) is replaced, the correct vehicle mileage and Vehicle Identification Number (VIN) must be programmed into PCM to prevent Diagnostic Trouble Codes (DTC) from being stored in Controller Anti-Lock Brake (CAB) module and Air Bag Control Module (ACM). See PROGRAMMING .
• On models equipped with a Sentry Key Immobilizer Module (SKIM), if PCM is replaced, the secret key data must also be updated to enable engine starting. To update secret key data, see PROGRAMMING .