U2151

CIRCUIT DESCRIPTION
The navigation display head (NDH) communicates with the navigation module (NAV) 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 display head (NDH) must detect a power mode transition from the OFF-ASLEEP state to one of the following:
^ ACC
^ ON

The navigation display head (NDH) does not set this DTC if B1327 or B1328 is current.

CONDITIONS FOR SETTING THE DTC
There is no response from the NAV when queried by the NDH.

The NDH does not receive a command from the NAV after 15 seconds.

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 NDH receives a response from the NAV.

DIAGNOSTIC AIDS
^ Test for intermittent shorts and opens on the navigation display serial data high circuit and the navigation display serial data low circuit.
^ Test for intermittent shorts and opens 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.