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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 448 (Engine Controls Self-Diagnostics - 6.0L Bi-Fuel & CNG) >> Diagnostic Tests >> DTC P1204: Vehicle Does Not Start On CNG >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 GMC Savana and 2003 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check - Alternative Fuels - Engine Controls. If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ALTERNATIVE FUELS - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Using a scan tool, observe the DTC information. If any DTCs are set, go to next step. If no DTCs are set go to step  5.
  3. Using a scan tool, select Captured Info in order to store the powertrain DTC information. After storing DTC information, go to next step.
  4. Turn ignition on, with engine off. Using a scan tool, observe the DTC information. If the scan tool displays DTC P0005, P0191, P0611, P2146, or P2665, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If the scan tool does not display DTC P0005, P0191, P0611, P2146, or P2665 go to next step.
  5. Attempt to start the engine. If the engine starts and idles, go to next step. If the engine does not start and idle, go to step  7.
  6. Observe the Freeze Frame and/or the Failure records data for this DTC. Turn the ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running The DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame and/or the Failure records data. If the DTC failed this ignition cycle, go to next step. If the DTC did not fail this ignition cycle, see DIAGNOSTIC AIDS .
  7. Turn ignition on, with engine off. using a scan tool, observe the Fuel Rail Pressure (FRP) sensor parameter. If the FRP display remain steady near 160 psi (1103 kPa), see NO-START - ENGINE CRANKS OKAY under NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article. If the FRP display does not remain steady near 160 psi (1103kPa), see FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 6.0L CHEVY EXPRESS, SAVANA, SIERRA & SILVERADO - BI-FUEL & CNG article.
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