Service Precautions

Before proceeding with diagnosis, following precautions must be observed:

• Ensure vehicle has a fully charged battery and functional charging system.
• Visually inspect connectors and wiring of circuit being worked on.
• DO NOT disconnect battery or Powertrain Control Module (PCM) unless instructed to do so. Doing so will erase any fault codes stored in PCM. Turn ignition off before disconnecting battery or damage to PCM may result.
• DO NOT cause short circuits when performing electrical tests. DO NOT disconnect sensors with ignition on. Either procedure will set additional fault codes making diagnosis of original problem more difficult.
• DO NOT use a test light in place of a voltmeter.
• When checking for spark, DO NOT hold coil wire more than 1/4" from ground. Damage to vehicle electronics and/or PCM may result.
• DO NOT prolong testing of fuel injectors. Engine may hydrostatically (liquid) lock.