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Glow Plug System Diagnosis

  1. If powertrain OBD system check has been performed, go to next step. If powertrain OBD system check has not been performed, perform powertrain OBD system check. See POWERTRAIN OBD SYSTEM CHECK in TESTS W/CODES - 6.5L TURBO DIESEL article.
  2. Retrieve DTCs. If DTC P0117, P0118 and/or P0380 does not exist, go to next step. If DTC P0117, P0118 and/or P0380 exist, perform appropriate DTC test. See TESTS W/CODES - 6.5L TURBO DIESEL article.
  3. Turn ignition switch to LOCK position. Disconnect all glow plug harness connectors. Using a test light connected to battery voltage, probe each glow plug spade terminal at glow plugs. If test light illuminates at each glow plug, go to next step. If test light does not illuminate at each glow plug, go to step 9).
  4. Ensure all glow plug harness connectors are still disconnected. Turn ignition switch to RUN position. Using scan tool, command glow plugs on. Using a test light connected to ground, probe each glow plug harness connector terminal. If test light illuminates at each glow plug harness connector, go to next step. If test light does not illuminate at each glow plug harness connector, go to step 10).
  5. Using scan tool, command glow plugs off. Using a test light connected to ground, probe each glow plug harness connector terminal. If test light illuminates at any glow plug harness connector, go to next step. If test light does not illuminate at any glow plug harness connector, glow plug circuit is okay at this time.
  6. Remove glow plug relay. Using scan tool, command glow plugs off. Using a test light connected to ground, probe each glow plug harness connector terminal. If test light illuminates at any glow plug harness connector, go to next step. If test light does not illuminate at any glow plug harness connector, go to step 8).
  7. Repair short to voltage in appropriate glow plug control circuit, between glow plug and glow plug relay.
  8. Check relay power, ground and control circuits. See GLOW PLUG RELAY . If problem exists, repair as necessary. If problem does not exist, replace glow plug relay.
  9. Replace glow plugs that did not illuminate test light.
  10. Repair open in glow plug circuit(s) that test light did not illuminate.
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