Circuit Description

The Class-II serial data line is used to communicate information between modules. Each module connected to the serial data line is assigned its own recognition code (address). This DTC is used to identify which modules are communicating. Modules communicate with each other by periodically sending State Of Health (SOH) messages.

When ignition switch is in RUN position, each module communicating on the serial data line sends a SOH message every 2 seconds (one second for PCM) to ensure that system is operating properly.

When ignition is turned on, most modules must learn initialization data from other modules on the serial data line, such as panel dimming or personalization. When this module requests initialization data from another module, and that request is not acknowledged after 5 seconds, module sets an initialization error DTC U1255.

Conditions of setting DTC:

• Module does not receive required initialization data on Class-II serial data line. Module retries request for 5 seconds, then sets DTC.
• This DTC only sets if DTC B1327, B1328, B1982, B1983, U1300 or U1301 is not current in module memory.