Test L: Fuel Indicator Light Inoperative (CNG)

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.
Turn ignition off and wait 30 seconds. Monitor Fuel Indicator Lamp (FIL) located in fuel gauge select switch button located to left of steering column. Turn ignition on. If FIL illuminates for two second bulb check and then turns off, go to next step. If FIL does not illuminate for two second bulb check and turn off, go to step 4.
Start engine and allow to idle. Monitor FIL. If FIL is illuminated while engine is running, go to TEST K: FUEL INDICATOR LIGHT ALWAYS ON (CNG) . If FIL is not illuminated while engine is running, system is okay at this time.
Remove fuel gauge select switch from instrument panel. Connect test light between ground and fuel gauge select switch connector terminal "C" (Red wire). Turn ignition on. If test light illuminates, go to next step. If test light does not illuminate, go to step 7.
Connect test light between fuel gauge select switch connector terminals "B" (Purple wire) and "C" (Red wire). Monitor test light and turn ignition on. If test light illuminates for at least a two seconds during bulb check, go to step 8. If test light does not illuminate for at least a two seconds during bulb check, go to next step.
Turn ignition off and wait 30 seconds. Disconnect Alternate Fuel Engine Control Unit (AF ECU) connectors. AF ECU is located in left front of engine compartment. Using DVOM, check for continuity of Purple wire between AF ECU Blue connector C001 terminal No. 4 and fuel gauge select switch connector terminal "B". See Figure. Continuity should be indicated. Check for poor connections at AF ECU and fuel gauge select switch. Check for short to voltage in Purple wire between AF ECU and fuel gauge select switch. Repair as necessary. After repairs, go to step 10. If circuit and connections are okay, go to step 9.
Repair open in Red wire between the fuel gauge select switch connector terminal "C" and ignition relay located in left front of engine compartment. Open condition may be a disconnected CNG harness connector. After repairs, go to step 10.
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.
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.
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.