GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2001 🢒 Seville - RHD 🢒 DTC 🢒 DTC U2150

Circuit Description

The navigation module (NAV) communicates with the navigation display head (NDH) over two dedicated lines. These are the navigation display serial data high circuit and the navigation display serial data low circuit.

Conditions for Running the DTC

The navigation module (NAV) must detect a power mode transition from the OFF-ASLEEP state to one of the following:

    • ACC
    • ON

DTCs B1327 and B1328 are not current.

Conditions for Setting the DTC

There is no response from the NDH when queried by the NAV.

The NAV does not receive a message from the NDH after three attempts, which occur once every three seconds (no communication for 9 seconds total).

Action Taken When the DTC Sets

The display does not update or change functions or the screen may become blank.

The message LOSS OF COMMUNICATION WITH NAVIGATION PROCESSOR may appear on the display.

Conditions for Clearing the DTC

The NAV receives a response from the NDH.

Diagnostic Aids
    • Test for intermittents on the navigation display serial data high circuit and the navigation display serial data low circuit.
    • Test for intermittents on the navigation module (NAV) supply and ground circuits.

Refer to Testing for Electrical Intermittents in Wiring Systems.

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. Tests that the navigation display serial data high and low circuits are within the correct voltage range.

Step

Action

Value(s)

Yes

No

Schematic Reference: Navigation System Schematics

1

Did you perform Diagnostic System Check - Navigation System ?

--

Go to Step 2

Go to Diagnostic System Check - Navigation System

2

Important:: The communications circuits are not at a constant steady voltage level.

  1. Turn OFF the ignition.
  2. Disconnect the navigation display head (NDH) connector C1.
  3. Turn ON the ignition with the engine off.
  4. Measure the voltage between the following:
    5. • The navigation display serial data high circuit and ground
    • The navigation display serial data low circuit and ground

Is the voltage within the range specified?

2.0 - 3.0 V

Go to Step 5

Go to Step 3

3

Test the following circuits for an open, a short to ground, a short to voltage or shorted together:

    • The navigation display serial data high circuit
    • The navigation display serial data low circuit

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 8

Go to Step 4

4

Inspect for poor connections at the harness connector of the navigation display head (NDH). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 8

Go to Step 5

5

Replace the navigation display head (NDH). Refer to Navigation Display Module Replacement .

Did you complete the replacement?

--

Go to Step 8

--

6

Inspect for poor connections at the harness connector of the navigation module (NAV). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 8

Go to Step 7

7

Replace the navigation module (NAV). Refer to Navigation Data Processor Replacement .

Did you complete the replacement?

--

Go to Step 8

--

8
  1. Use the scan tool in order to clear DTCs.
  2. Turn OFF the ignition.
  3. Disconnect the scan tool.
  4. Open, then close the vehicle door to cancel the RAP mode.
  5. Do not operate any vehicle system for two minutes.
  6. Turn ON the ignition with the engine off.
  7. Wait 20 seconds, then connect a scan tool.
  8. Use the scan tool to retrieve DTCs.

Does the DTC reset?

--

Go to Step 2

System OK