GM Service Manual Online
For 1990-2009 cars only

Tools Required

J 39200 Digital Multimeter

  1. Inspect the routing of the wires. Improper routing can cause cross firing.
  2. Inspect each wire for any signs of cracks or splits in the wire.
  3. Inspect each boot for the following conditions:
  4. • Tearing
    • Piercing
    • Arc through
    • Carbon Tracking
    • If the boot needs to be replaced, replace the complete spark plug wire.

Spark Plug Wire Resistance Check

  1. Remove the spark plug wire to be tested. Verify that the wire terminals are clean.
  2. Set the ohmmeter on the high scale.
  3. Connect the test leads to each end of the wire being tested.
  4. Twist the wire gently while watching the ohmmeter.
  5. If the ohmmeter reads above 2,400 ohms (no matter how long the wire is), or fluctuates from infinity to any value, replace the spark plug wire.
  6. If the resistance of any spark plug wire tested is not within the following ranges, replace the spark plug wire being tested.
  7. • 0-380 mm (0-15 in) long spark plug wire = 0-750 ohms.
    • 380-635 mm (15-25 in) long spark plug wire = 0-1,250 ohms.
    • 635-889 mm (25-35 in) long spark plug wire = 0-1,750 ohms.
    • Longer wire - the measured resistance should not exceed approximately 1,968 ohms per meter (600 ohms per foot).