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 Diagrams.

TEST DESCRIPTION

Steps 1-8:

The number(s) below refer to the step number(s) on the diagnostic table.
1. Determines if the malfunction is present.
2. Tests that the navigation display serial data high and low circuits are within the correct voltage range.