Engine Controls - System & Component Testing - Bi-Fuel - Gasoline/CNG: Introduction
WARNING:
Before performing any tests or diagnostics on CNG components or systems, read all cautions and warnings in CNG/LPG SAFETY PRECAUTIONS article in GENERAL INFORMATION.
NOTE:
System and component testing included in this article is for alternative fuel systems only. For gasoline fuel system and component testing, see SYSTEM & COMPONENT TESTING - GASOLINE
article. Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) when a malfunction occurs, check for Powertrain Control Module (PCM) DTCs and Alternative Fuel Control Module (AFCM) DTCs prior to testing an individual system or component. Perform QUICK TEST
procedures in SELF-DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article, or QUICK TEST
procedures in SELF-DIAGNOSTICS - BI-FUEL - GASOLINE/CNG article. If no DTCs are present, perform SYMPTOM DIAGNOSIS
under SYMPTOMS in TROUBLE SHOOTING - NO CODES - BI-FUEL - GASOLINE/CNG article to diagnose driveability problems existing when a hard fault code is not present. For specifications, see appropriate ON-VEHICLE ADJUSTMENTS - TRUCKS
or SERVICE & ADJUSTMENT SPECIFICATIONS - EXCURSION & PICKUP
article.
NOTE:
Testing individual components does not isolate short or open circuits. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter to isolate shorted or open wiring harness. For identification of circuits and terminals referenced in test procedures, see ENGINE PERFORMANCE
in SYSTEM WIRING DIAGRAMS - F150 article in ELECTRICAL.