Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2006CHEVY EXPRESS G2500, VAN CARGO, 6.6 2REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1534 (DATA COMMUNICATION SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESSCAN TOOL DOES NOT COMMUNICATE WITH LOW SPEED GMLAN DEVICECIRCUIT/SYSTEM TESTINGTESTING THE SERIAL DATA CIRCUIT FOR AN OPEN/HIGH RESISTANCE
2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2
Testing the Serial Data Circuit for an Open/High Resistance
2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2SECTION Testing the Serial Data Circuit for an Open/High Resistance
WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
- If equipped with a JX 339 splice pack, ignition ON, verify the scan tool communicates with one or more control modules connected to the JX 339 splice pack.
- If all control modules on the JX 339 spice pack do not communicate, test the serial data circuit between the JX 221 and JX 339 splice packs for an open/high resistance. If the circuit tests normal, test each splice pack for an open/high resistance.
- Ignition OFF, disconnect one of the harness connectors listed below:
- JX 221 if the control modules not communicating are connected to the JX 221 splice pack
- JX 223 if the control modules not communicating are connected to the JX 223 splice pack, if equipped
- JX 339 if the control modules not communicating are connected to the JX 339 splice pack
- Install a 3A fused jumper wire between the disconnected splice pack connector terminal listed below and a low speed GMLAN serial data circuit that is not communicating:
- JX 221 terminal D
- JX 223 terminal A
- JX 339 terminal A
- Ignition ON, verify the scan tool communicates with the control modules connected to the low speed GMLAN serial data circuit.
- If any control module does not communicate, test each section of the serial data circuit for an open/high resistance. If the circuits test normal, replace the control module that does not communicate when connected.
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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.