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Test K: Fuel Indicator Light Always On (CNG)

  1. If powertrain diagnostic system check (CNG) has been performed, go to next step. If powertrain diagnostic system check (CNG) has not been performed, go to POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 2.2L & 2.4L "J" & "N" BODIES - GASOLINE & CNG article in ENGINE PERFORMANCE. After performing powertrain diagnostic system check (CNG), go to next step.
  2. Turn ignition off and wait 30 seconds. Monitor Fuel Indicator Light (FIL) located in fuel gauge select switch on left side of steering column. Turn ignition on. If FIL illuminates for at least a two seconds during bulb check, go to next step. If FIL does not illuminate for at least a two seconds during bulb check, go to TEST L: FUEL INDICATOR LIGHT INOPERATIVE (CNG) .
  3. Start engine and allow to idle. Monitor FIL. If FIL is illuminated while engine is running, go to next step. If FIL is not illuminated while engine is running, system is operating properly at this time.
  4. Using scan tool, establish communication with Alternate Fuel Engine Control Unit (AF ECU). Observe natural gas operation enable parameters and determine if engine is operating on gasoline or CNG. If engine is operating on gasoline, go to next step. If engine is not operating on gasoline, go to step  6.
  5. Determine cause of gasoline engine operation. Possible causes include: empty CNG fuel tank, inaccurate Fuel Pressure Sensor (FPS) indicates NO CNG FUEL when tank has fuel or an AF ECU DTC is set. Fill CNG tank or repair vehicle as necessary. If AF ECU DTC is set, go to SELF-DIAGNOSTICS - 2.2L & 2.4L "J" & "N" BODIES - GASOLINE & CNG article in ENGINE PERFORMANCE. If problem is found and repaired, go to step  10. If problem is not found and repaired, go to FUEL SYSTEM UNWANTED SWITCH TO GASOLINE (CNG) under FUEL SYSTEM in SYSTEM & COMPONENT TESTING - CARS - EXCEPT METRO & PRIZM article.
  6. Remove fuel gauge select switch from instrument panel. Connect test light between fuel gauge select switch connector terminals "B" (Purple wire ) and "C" (Red wire). Start engine and allow to idle. If test light illuminates, go to next step. If test light does not illuminate, go to step  8.
  7. Turn ignition off and wait 30 seconds. Disconnect AF ECU connectors. AF ECU is located in left front of engine compartment. Check for short to ground in Purple wire between fuel gauge select switch connector terminal "B" and AF ECU Blue connector C001 terminal No. 4. See Figure. Repair as necessary. After repairs, go to step  10. If circuit is okay, go to step  9.
  8. Replace fuel gauge select switch assembly. See FUEL GAUGE SELECT SWITCH under FUEL SYSTEMS in REMOVAL, OVERHAUL & INSTALLATION - CARS article in ENGINE PERFORMANCE. After repairs, go to step  10.
  9. Replace AF ECU. See ALTERNATIVE FUEL ENGINE CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CARS article in ENGINE PERFORMANCE. After repairs, go to next step.
  10. Remove all test equipment except scan tool. Reconnect any disconnected components. Using scan tool, clear DTCs from AF ECU and PCM. Turn ignition off and wait 30 seconds. Start engine and operate vehicle. Monitor FIL and MIL operation. Observe vehicle performance and driveability. After operating vehicle check for DTCs in AF ECU and PCM. If vehicle operates on CNG with normal driveability, no FIL/MIL illumination and no set DTCs, system is okay. If vehicle does not operate on CNG with normal driveability, or FIL/MIL are illuminated or DTCs are set, go to POWERTRAIN DIAGNOSTIC SYSTEM CHECK (CNG) under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 2.2L & 2.4L "J" & "N" BODIES - GASOLINE & CNG article in ENGINE PERFORMANCE.
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