Engine Electrical Diagnostic System Check

Ensure battery condition, cold cranking amperage and reserve capacity meet specifications. Replace as necessary, then go to next step.
Install scan tool to Data Link Connector (DLC). Turn ignition on, with engine off. If scan tool powers up, go to next step. If scan tool does not power up, go to TEST B: SCAN TOOL DOES NOT POWER UP under SYSTEM TESTS.
Turn ignition on, with engine off. Attempt to communicate with each of the following modules on the class 2 serial data circuit:
- Body Control Module (BCM).
- Instrument Panel Module (IPM).
- Memory Seat Module.
- OnStar(R) (ONS).
- Radio (IRC).
- Powertrain Control Module (PCM).
If scan tool communicate with all modules, go to next step. If scan tool does not communicate with all modules, go to TEST A: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE under SYSTEM TESTS.
Using a scan tool, select DISPLAY DTCs function for each module. If using a Tech 2 scan tool, use CLASS 2 DTC CHECK feature to determine which modules have DTCs set. On all applications, record all displayed DTCs, DTC status, and module which set DTC. If scan tool displays any DTCs, go to next step. If scan tool does not display any DTCs, repair charging system as necessary. See GENERATORS & REGULATORS - CATERA.
If scan tool does not display any DTCs which begin with a "U", go to next step. If scan tool displays any DTCs which begin with a "U", go to TEST A: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE under SYSTEM TESTS.
If scan tool displays DTCs B055, B1556, or B1558, perform appropriate test in accordance with DTC retrieved. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If scan tool does not display DTCs B055, B1556, or B1558, repair system voltage out-of-range condition. See GENERATORS & REGULATORS - CATERA article.