U1865

DTC U1865

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions)provides an overview of each diagnostic category.

DTC Descriptor
DTC U1865
- Fuel Operated Heater Lost Communication with Engine Control Module

Circuit/System Description

Control modules connected to the serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the control modules. The control modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.

Conditions for Running the DTC

* The system voltage is between 9-16 V.
* The vehicle power mode master indicates that the need for serial data communications.

Conditions for Setting the DTC

A supervised periodic message that includes the transmitter module availability has not been received.

Action Taken When the DTC Sets

The control module is never signaled. Therefore, the specific subsystems will not function.

Conditions for Clearing the DTC

* A current DTC clears when the malfunction is no longer present.
* A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Circuit/System Verification

Verify that U0100 is not set.

If the DTC is set, refer to DTC U0100-U02FF (U0100).