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HOMESERVICE MANUALSCHEVROLET1999CUTAWAY 7.4 JREPAIR AND DIAGNOSIS (SINGLE PAGE)BODY & FRAMEDOOR LOCKSANTI-THEFT SYSTEMDIAGNOSTIC TESTSDTC U1193: LOSS OF VIM CLASS 2 COMMUNICATIONTESTING PROCEDURE
1999 Chevrolet Cutaway 7.4 J

Testing Procedure

1999 Chevrolet Cutaway 7.4 JSECTION Testing Procedure
  1. Perform the diagnostic system operation check for the module which does not communicate to ensure that the module is properly powered. See DIAGNOSTIC SYSTEM OPERATION CHECK - ANTI-THEFT (EXPORT)  under TROUBLE SHOOTING. A module which loses power during an ignition cycle will cause other module(s) to set lost communication DTCs. If a repair was made when the diagnostic system operation check was made, go to step  6. If a repair was not made, go to the next step.
  2. Test the class 2 serial data circuit of the module that is not communicating for an open between itself and the module reporting the u-code. The malfunction may be due to an open in the class 2 serial data circuit or an open in the module circuit. See DATA LINK COMMUNICATIONS - CUTAWAY, EXPRESS, RV CUTAWAY, SAVANA, SAVANA CAMPER SPECIAL & SAVANA SPECIAL article. If you find and correct the condition, got to step  5. If you do not find and correct the condition, go to the next step.
  3. Inspect for poor connections/terminal tension at the class 2 serial data circuit(s) of the module that is not communicating. See DATA LINK COMMUNICATIONS - CUTAWAY, EXPRESS, RV CUTAWAY, SAVANA, SAVANA CAMPER SPECIAL & SAVANA SPECIAL article. If you find and correct the condition, go to step  5. If you do not find and correct the condition, go to the next step.
  4. Replace the module that is not communicating. For Vehicle Theft Deterrent Passlock™ Module (VTD), go to REMOVAL & INSTALLATION . For other modules, refer to appropriate article. See DATA LINK COMMUNICATIONS - CUTAWAY, EXPRESS, RV CUTAWAY, SAVANA, SAVANA CAMPER SPECIAL & SAVANA SPECIAL article. After replacement, go to step  7.
  5. Install the scan tool. Turn on the ignition leaving the engine off. Select the display DTCs function for the module which was not communicating. If the scan tool displays any DTCs which do not begin with U, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS (EXPORT) table. If the scan tool does not display any DTCs which do not begin with U, go to the next step.
  6. Clear the DTCs using the scan tool. The module which was not communicating due to an open in the class 2 serial data circuit and may have set lost communication DTCs for those modules that it was monitoring. After repair, go to the next step.
  7. Select the display DTCs function for the module(s) which had the lost communications with XXX DTC set. If the scan tool displays any DTCs which do not begin with a U, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS (EXPORT)  table. If the scan tool does not display any DTCs any DTCs which do not begin with U, go to the next step.
  8. Clear the DTCs using the scan tool. Continue diagnosing or clearing the DTCs until all the modules have been diagnosed and all the DTCs have been cleared. The modules which can communicate indicate the module which cannot communicate. You must clear the DTC from these modules to avoid future misdiagnosis. After repair, the system is OK.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.