U1152 Class 2 Lost Communication With HTR- A/C Programmer

DTC U1152: Class 2 Lost Communication With The Heater And A/C Programmer:

DTC U1152: Class 2 Lost Communication With The Heater And A/C Programmer:

CIRCUIT DESCRIPTION
Modules connected to the Class 2 data link monitor the link for serial data communications during normal vehicle operation. Operating information (Report messages) and commands (Load messages) are exchanged among the modules. When a module receives a Report or Load message for a critical operating parameter, the module records the Source ID of the module which sent the message for State Of Health (SOH) monitoring (Node Alive Messages). A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. Once a Source ID is learned by a module, it will monitor for that Source ID's Node Alive message. Each module on the Class 2 data link which is powered and performing functions that require detection of communication malfunctions is required to send a Node Alive message every two seconds. When no message is detected from a learned Source ID (the Heater and A/C programmer) for five seconds, a DTC U1152 is set.

CONDITIONS FOR SETTING THE DTC
The SBM does not receive a state of health message from the Heater and A/C Programmer.

ACTION TAKEN WHEN THE DTC SETS
^ Stores a DTC U1152 in the SBM memory.
^ No driver warning message will be displayed for this DTC.

CONDITIONS FOR CLEARING THE DTC
^ Under all fault conditions, the ignition must be cycled before this DTC can change from current to history.
^ The SBM detects a state of health message from the Heater and A/C Programmer.
^ A history DTC will clear after 50 consecutive ignition cycles if the condition for the malfunction is no longer present.
^ Using the on-board (clear DTCs) feature.
^ Using a scan tool.

DIAGNOSTIC AIDS
The following conditions may cause an intermittent malfunction to occur:
^ An intermittent power or ground loss to the Heater and A/C Program men
^ Poor connections at the SBM, or the Heater and A/C Programmer.

TEST DESCRIPTION
Numbers below refer to the step numbers on the diagnostic table.
1. Always perform the SBM Diagnostic System Check before attempting to diagnose a DTC U1152. Diagnostic System Check - Body Control Module (SBM)
2. The Scan tool tries to communicate with the Heater and A/C Programmer.
3. The Scan tool tries to communicate with the other modules.
4. This test checks for a poor connection at the Heater and A/C Programmer.
6. This test checks for loss of power or ground to the Heater and A/C Programmer.