GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2007 🢒 Caprice WM 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC U1401

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category

DTC Descriptor

DTC U1401: Lost Communications Between AD and ADG

Circuit/System Description

The navigation interface module (NIM) continuously sends a communication signal to the navigation module. Upon receiving the signal, the navigation module sends a reply signal, confirming that it can communicate.

Conditions for Running the DTC
    • The ignition ON
    •  The system voltage is at least 9.5 volts and no more than 15.5 volts.

Conditions for Setting the DTC

The NIM does not receive a response from the navigation module for 5 or more consecutive seconds.

Action Taken When the DTC Sets

The navigation system is disabled.

Conditions for Clearing the DTC
    • The current DTC will clear when the NIM receives a communication reply from the navigation module.
    • The history DTC will clear after 50 fault-free ignition cycles have occurred.

Reference Information

Schematic Reference

Radio/Navigation System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Navigation System Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References

Circuit/System Testing
  1. Disconnect the X1 harness connector at the Navigation Module.
  2. Ignition OFF, test for less than 10 Ω between the ground circuit terminal A8 and ground
    3. ⇒If greater than specified range, test the ground circuit for an open/high resistance.
  3. Ignition On, test for B+ between the B+ circuit terminal  A4 and ground.
    4. ⇒If less than the specified value, test the circuit for a short to ground or an open/high resistance.
  4. Ignition ON, Navigation ON, test for B+ between the control circuit terminal A7 and ground.
    5. ⇒If less than the specified value, test the circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the Navigation Interface Module.
  5. Ignition OFF, disconnect the harness connector at the Navigation Interface Module and the X3 harness connector at the Navigation Module.
  6. Test for less than 1 Ω between the serial data terminals listed below:
    7. • Terminal 1 at the Navigation Interface Module and terminal C7 X3 at the Navigation Module.
    • Terminal 7 at the Navigation Interface Module and terminal C8 X3 at the Navigation Module.
    ⇒If greater than the specified range, test the circuit for an open/high resistance.
  7. Test for infinite resistance between the serial data terminals listed below and ground:
    8. • Terminal 1 at the Navigation Interface Module.
    • Terminal 7 at the Navigation Interface Module.
    ⇒If less than the specified value, test the circuit for a short to ground.
  8. Test for less than 1 V between the serial data terminals listed below and ground:
    9. • Terminal 1 at the Navigation Interface Module.
    • Terminal 7 at the Navigation Interface Module.
    ⇒If greater than the specified range, test the circuit for a short to voltage.
  9. If all circuits test normal, replace the Navigation Module.

Repair Instructions

Perform the Diagnostic Repair Verification.

Control Module References for Navigation Interface module and Navigation Module replacement, setup, and programming.