Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.
Note. For removal and installation of Bi-Fuel and CNG related components, see REMOVAL & INSTALLATION - SIERRA & SILVERADO - BI-FUEL & CNG article. For removal and installation of gasoline related components, see REMOVAL & INSTALLATION - SIERRA & SILVERADO - FLEX-FUEL & GASOLINE article.
Circuit Description
The Fuel Injector Control Module (FICM) monitors the CNG Fuel Tank Pressure (FTP) sensor voltage, the Fuel Tank Temperature (FTT) sensor voltage, and the Fuel Rail Temperature (FRT) sensor voltage. The FTP, FTT, and FRT sensor values, and diagnostic data, is communicated to the Powertrain Control Module (PCM) by 2 Pulse Width Modulated (PWM) circuits. This DTC sets when the PCM does not receive any PWM signals from the FICM.
Test Description
The number below refers to the step number on the diagnostic table.
- 2 This step verifies that the condition is active.
- 3 This step verifies that the ignition voltage circuit to the FICM is OK. If the ignition voltage circuit is open, DTCs P1207, P1208, and P1209 may also be set.