Pinpoint Test AC: DTC U0256:00

Climate Control System

Pinpoint Test AC: DTC U0256:00

Normal Operation

- DTC U0256:00 (Lost Communication With Front Controls Interface Module (FCIM) "A")- sets in continuous memory in the HVAC module if data messages received from the FCIM (Front Controls Interface Module) over the Medium Speed Controller Area Network (MS-CAN) are missing for 5 seconds or more. For a complete list of all network messages, refer to Information Bus.

This pinpoint test is intended to diagnose the following:

- FCIM (Front Controls Interface Module)

- HVAC module

PINPOINT TEST AC : DTC U0256:00

AC1 VERIFY THE CUSTOMER CONCERN

- Ignition ON.

- Verify there is an observable symptom present.

Is an observable symptom present?

Yes
GO to AC2.
No
The system is operating normally at this time. The DTC may have been set due to high network traffic or an intermittent fault condition.

AC2 CHECK THE COMMUNICATION NETWORK

- Ignition ON.

- Enter the following diagnostic mode on the scan tool: Network Test.

- Carry out the network test.

Does the FCIM (Front Controls Interface Module) pass the network test?

Yes
GO to AC3.
No
REFER to Information Bus.

AC3 RETRIEVE THE RECORDED DTCs FROM THE FCIM (Front Controls Interface Module) SELF-TEST

- Check for recorded DTCs from the FCIM (Front Controls Interface Module) self-test.

Is DTC U3003:16 or DTC U3003:17 recorded?

Yes
REFER to Accessories and Optional Equipment.
No
GO to AC4.

AC4 RETRIEVE THE RECORDED DTCs FROM THE HVAC MODULE SELF-TEST

- Check for recorded DTCs from the HVAC module self-test.

Is DTC U3003:16 or DTC U3003:17 recorded?

Yes
GO to Pinpoint Test H. Pinpoint Test H: DTC U3003:16 Or U3003:17
No
GO to AC5.

AC5 RECHECK THE HVAC MODULE DTCs
NOTE: If new modules were installed prior to the DTC being set, the module configuration may be incorrectly set during the Programmable Module Installation (PMI) or the PMI (Programmable Module Installation) may not have been carried out.

- Clear the DTCs.

- Wait 10 seconds.

- Repeat the HVAC module self-test.

Is DTC U0256:00 still present?

Yes
GO to AC6.
No
The system is operating correctly at this time. The DTC may have been set due to high network traffic or an intermittent fault condition.

AC6 CHECK FOR DTC U0256:00 SET IN OTHER MODULES

- Clear all DTCs.

- Ignition OFF.

- Ignition ON.

- Wait 10 seconds.

- Enter the following diagnostic mode on the scan tool: Self-Test.

- Retrieve the continuous memory DTCs from all modules.

Is DTC U0256:00 set in the Accessory Protocol Interface Module (APIM)?

Yes
INSTALL a new FCIM (Front Controls Interface Module). CLEAR the DTCs. REPEAT the self-test.
No
INSTALL a new HVAC module. TEST the system for normal operation.