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HOMESERVICE MANUALSCHEVROLET2006CHEVY EXPRESS G2500, VAN CARGO, 6.6 2REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 663 (COMPUTER/INTEGRATING SYSTEMS)DIAGNOSTIC INFORMATION AND PROCEDURESDTC U1881-U1899TEST DESCRIPTION

2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2

Test Description

2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2SECTION Test Description

WARNING: This page is about a different car, the 2006 GMC Sierra, 2006 GMC Cab & Chassis Sierra, 2006 Chevrolet Silverado, and 2006 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The number below refers to the step number on the diagnostic table.

4: The hydraulic motor EHPS 42 V battery voltage circuit includes a 125 A EHPS fuse inline, which is part of the 42-volt harness, below the starter/generator control module next to C121.
9: The module which was not communicating may have set Loss of Communication DTCs for those modules that it was monitoring.

DTC U1881-U1899

Step	Action	Yes	No
Schematic Reference: Data Link Connector (DLC) Schematics Connector End View Reference: Master Electrical Component List and Inline Harness Connector End Views in Wiring Systems
1	Did you perform the Diagnostic System Check - Vehicle?	Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Was any DTC in the range U1001-U1254 recorded?	Go to DTC U1001-U1254	Go to Step 3
3	Was any DTC in the range U0100-U0299 recorded?	Go to DTC U0100-U0299 (Diesel Engine) or DTC U0100-U0299 (HP2)	Go to Step 4
4	IMPORTANT: Use the DTC Descriptors list in order to determine which module is not communicating. If multiple DTCs were set, consider the closest module to the powertrain control module (PCM) as the non-communicating module. A loss of voltage to the electro-hydraulic power steering (EHPS) hydraulic motor as well as to the module may cause a loss of communication. Test the following circuits of the module that is not communicating for an open or a short to ground: The battery positive voltage input circuits The battery positive voltage output circuits The ignition voltage input circuits The ignition voltage output circuits The switched battery positive voltage circuits The EHPS 42 V battery voltage circuit. Refer to the following: Control Module References for the applicable schematic Circuit Testing in Wiring Systems Wiring Repairs in Wiring Systems Did you find and correct the condition?	Go to Step 9	Go to Step 5
5	IMPORTANT: A loss of ground to the electric-hydraulic power steering (EHPS) hydraulic motor as well as to the module may cause a loss of communication. Turn OFF the ignition. Test the ground circuits of the module that is not communicating for an open. Refer to the following: Control Module References for the applicable schematic Circuit Testing in Wiring Systems Wiring Repairs in Wiring Systems Did you find and correct the condition?	Go to Step 9	Go to Step 6
6	Test the class 2 or/and high speed GMLAN serial data circuits of the module that is not communicating for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 9	Go to Step 7
7	Inspect the harness connectors of the module that is not communicating for poor connections and terminal tension at the following circuits: The battery positive voltage input circuits The battery positive voltage output circuits The ignition voltage input circuits The ignition voltage output circuits The switched battery positive voltage supply circuits The ground circuits The class 2 or/and high speed GMLAN serial data circuits Refer to the following: Control Module References for the applicable schematic Testing for Intermittent Conditions and Poor Connections in Wiring Systems Connector Repairs in Wiring Systems Did you find and correct the condition?	Go to Step 9	Go to Step 8
8	Replace the module that is not communicating. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement?	Go to Step 9	-
9	Install a scan tool. Turn ON the ignition with the engine OFF. Select the Display DTCs function for the module which was not communicating. Does the scan tool display any DTCs which do not begin with a "U"?	Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	Go to Step 10
10	Select the Display DTCs function for the modules which had the Loss of Communications DTC set. Does the scan tool display any DTCs which do not begin with a "U"?	Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	Go to Step 11
11	Use the scan tool in order to clear the DTCs. Continue diagnosing or clearing the DTCs until all the modules have been diagnosed and all the DTCs have been cleared. Did you complete the action?	System 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.