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Home >> Chevrolet >> 2000 >> C3500 HD 6.5 F, Standard >> Repair and Diagnosis >> Body & Frame >> Door Locks >> Anti-Theft System - Escalade, Express, Pickup, SAVANA, TAHOE & YUKON DENALI >> Diagnostic Tests >> DTC U1255: Class 2 Communication Malfunction >> Diagnostic Procedure

Diagnostic Procedure

  1. Turn ignition on. Using scan tool, attempt to communicate with VCM. If communication exists, go to next step. If no communication is possible, diagnose DLC. See DATA LINK CONNECTORS article in WIRING DIAGRAMS. After repairs, go to step  3.
  2. Turn ignition off. Disconnect 16-pin Passlock™ module connector. Measure resistance of Purple wire between Passlock™ module harness connector terminal B4 and DLC terminal No. 2. See Figure. If resistance is less than 10 ohms, replace Passlock™ module. See PASSLOCK™ MODULE  under REMOVAL & INSTALLATION. After repairs, go to next step. If resistance is 10 ohms or more, repair open in Purple wire. After repairs, go to next step.
  3. Turn ignition off. Reconnect all connectors and components. Turn ignition on. Using scan tool, clear all DTCs.
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