GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1998 🢒 Seville 🢒 Body and Accessories 🢒 Instrument Panel, Gauges, and Console 🢒 DTC U2151 Navigation ECU Communication Malfunction

Object Number: 262604 Size: MF

Circuit Description

While the Ignition Switch is in the ACC or RUN positions, the Navigation Display Module sends a State of Health (SOH) message to the Navigation Data Processor on the ND Data Bus every 30 seconds, or during System Inspection Mode, to ensure that the system is operating properly. The ND Data Bus communication signals are carried from pin 26 of the Navigation Data Processor connector C2 on circuit 1171 to pin 14 of the Navigation Display Module connector C2 and from pin 13 of the Navigation Data Processor connector C2 on circuit 1219 to pin 15 of the Navigation Display Module connector C2.

Conditions for Running the DTC

Navigation Display Module is running through System Inspection Mode.

Conditions for Setting the DTC

There is an open circuit between the Navigation Data Processor and the Navigation Display Module, and communication initialization fails after a regular number of retries.

Action Taken When the DTC Sets
    • No connection with Audio ECU appears on the display.
    • This failure will have no effect outside the Navigation System.

Conditions for Clearing the MIL/DTC
    • A current DTC will clear when the Navigation Display Module does not detect the failure during the last execution of the System Inspection Mode.
    • A history DTC will clear using a scan tool.

Diagnostic Aids
    • An intermittent may be caused by the following:
       - Mis-routed harness
       - Rubbed through wire insulation
       - Broken wire inside the insulation
    • Cycle the Ignition Switch even after a successful inspection with a scan tool so initialization will occur.
    • DTC U2151 will not set if DTC B1328, DTC B1327, or DTC U2150 is current.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. Determines if the malfunction is present.

    2.

  2. Checks circuit 1171 for a short to B+ condition.

    3.

  3. Checks circuit 1219 for a short to B+ condition.

    4.

  4. Checks circuit 1171 for a short to ground condition.

    5.

  5. Checks circuit 1219 for a short to ground condition.

    6.

  6. Checks circuit 1171 for an open condition.

    7.

  7. Determines if the malfunction is due to an internal fault in the Navigation Display Module or an open condition in circuit 1219.

Step

Action

Value(s)

Yes

No

1

Was the Navigation Diagnostic System Check performed?

--

Go to Step 2

Diagnostic System Check - Navigation System

2

  1. Disconnect the Navigation Data Processor connector C2.
  2. Measure the voltage between cavity 26 of the Navigation Data Processor harness connector C2 and ground with a DMM.

Is the voltage measured within the specified range?

0 V

Go to Step 3

Go to Step 4

3

Measure the voltage between cavity 13 of the Navigation Data Processor harness connector C2 and ground with a DMM.

Is the resistance measure within the specified range?

0 V

Go to Step 5

Go to Step 6

4

Repair the short to B+ in circuit 1171 between cavity 26 of the Navigation Data Processor connector C2 and cavity 14 of the Navigation Display Module connector C2. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 15

--

5

Measure the resistance between cavity 26 of the Navigation Display Module harness connector C2 and ground with a DMM.

Is the resistance measure within the specified range?

∞

Go to Step 7

Go to Step 8

6

Repair the short to B+ in circuit 1219 between cavity 13 of the Navigation Data Processor connector C2 and cavity 15 of the Navigation Display Module connector C2. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 15

--

7

Measure the resistance between cavity 13 of the Navigation Data Processor harness connector C2 and ground with a DMM.

Is the resistance measure within the specified range?

∞

Go to Step 9

Go to Step 10

8

Repair the short to ground in circuit 1171 between cavity 26 of the Navigation Data Processor connector C2 and cavity 14 of the Navigation Display Module connector C2. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 15

--

9

  1. Disconnect the Navigation Display Module connector C2.
  2. Measure the resistance between cavity 26 of the Navigation Data Processor harness connector C2 and cavity 14 of the Navigation Display Module harness connector with a DMM.

Is the resistance measured within the specified range?

0-2 ohms

Go to Step 11

Go to Step 12

10

Repair the short to ground in circuit 1219 between cavity 13 of the Navigation Data Processor connector C2 and cavity 15 of the Navigation Display Module connector C2. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 15

--

11

Measure the resistance between cavity 13 of the Navigation Data Processor harness connector C2 and cavity 15 of the Navigation Display Module harness connector C2 with a DMM.

Is the resistance measure within the specified range?

0-2 ohms

Go to Step 13

Go to Step 14

12

Repair the open in circuit 1171 between cavity 26 of the Navigation Data Processor connector C2 and cavity 14 of the Navigation Display Module connector C2. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 15

--

13

Replace the Navigation Display Module. Refer to Navigation Display Module Replacement in Instrument Panel, Gages, and Console.

Is the replacement complete?

--

Go to Step 15

--

14

Repair the open in circuit 1219 between cavity 13 of the Navigation Data Processor connector C2 and cavity 15 of the Navigation Display Module connector C2. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 15

--

15
  1. Clear DTC with the scan tool.
  2. Cycle the Ignition Switch.
  3. Perform Navigation Diagnostic System Check.

Has the test run and passed?

--

Diagnostic System Check - Navigation System

--