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Pinpoint Test O: U0100:00

WARNING: This page is about a different car, the 2023 Ford Bronco. However, it is still accessible from the selected car via links, so may be relevant.
  1. Normal Operation and Fault Conditions 

    The HVAC control module communicates with the PCM over the CAN. If messages are missing or not received from the PCM, features such as the A/C can be inoperative or can operate incorrectly, or the outside air temperature can be reporting incorrectly.

    DTC Fault Trigger Conditions 

    DTC Description Fault Trigger Condition
    HVAC U0100:00 Lost Communication With ECM/PCM 'A': No Sub Type Information Sets in continuous memory when the HVAC control module detects network messages are missing from the PCM for more than 5 seconds.

    Possible Sources 

    • Network communication concern
    • HVAC control module concern
    • PCM concern

  2. O1 VERIFY THE CONCERN

    • Ignition ON.

    • Verify there is an observable symptom present.

    Is an observable symptom present? 

    Yes  GO to O2 
    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.

  3. O2 VERIFY THE DIAGNOSTIC SCAN TOOL COMMUNICATES WITH THE PCM (POWERTRAIN CONTROL MODULE)

    • Connect the diagnostic tool.

    • Attempt to establish a vehicle session using the diagnostic scan tool.

    Can a vehicle session be established? 

    Yes  GO to O3 
    No  REFER to: Controller Area Network (CAN) Module Communications Network .

  4. O3 CHECK FOR NON-NETWORK DIAGNOSTIC TROUBLE CODES (DTCS)

    • Using a diagnostic scan tool, carry out the self-test for the HVAC control module setting the DTC.

    Are any non-network Diagnostic Trouble Codes (DTCs) present? 

    Yes  DIAGNOSE all non-network Diagnostic Trouble Codes (DTCs) first. REFER to Diagnostic Trouble Code (DTC) Chart .
    No  GO to O4 

  5. O4 CHECK FOR PCM (POWERTRAIN CONTROL MODULE) DIAGNOSTIC TROUBLE CODES (DTCS)

    • Using a diagnostic scan tool, carry out the PCM self-test.

    Are any non-network Diagnostic Trouble Codes (DTCs) present? 

    Yes  REFER to: Electronic Engine Controls . REFER to: Electronic Engine Controls .
    No  GO to O5 

  6. O5 RECHECK FOR DTC (DIAGNOSTIC TROUBLE CODE) U0100:00

    • Using a diagnostic scan tool, clear the Diagnostic Trouble Codes (DTCs) in the HVAC control module.

    • Ignition OFF.

    • Ignition ON.

    • Wait 10 seconds.

    • Using a diagnostic scan tool, carry out the self-test for the HVAC control module.

    Is DTC U0100:00 still present? 

    Yes  GO to O6 
    No  The system is operating correctly at this time. The DTC may have set due to high network traffic or an intermittent fault condition.

  7. O6 CHECK FOR OTHER CAUSES OF NETWORK COMMUNICATION CONCERN

    NOTE: If new modules were installed prior to the Diagnostic Trouble Code (DTC) being set, the module configuration can be incorrectly set during the Programmable Module Installation (PMI) or Programmable Module Installation (PMI) the may not have been carried out.

    • Check the vehicle service history for recent service actions related to the PCM and the module setting the DTC [ HVAC control module]. If recent service history is found:

      • verify correct replacement module was installed

        • vehicle parts build list may be used to verify correct part fit

      • verify the configuration of replacement module was correct

        • re-configure module using as-built data if prior configuration is suspect

      • verify the module was not obtained from a like vehicle and installed into vehicle with concern

        • return the swapped module to source vehicle and obtain new replacement module

    • Operate the system and determine if the observable symptom is still present.

    Is the observable symptom still present? 

    Yes  GO to O7 
    No  The system is operating correctly at this time. The concern may have been due to incorrect parts replacement procedures or incorrect module configuration.

  8. O7 CHECK FOR CORRECT PCM (POWERTRAIN CONTROL MODULE) OPERATION

    • Ignition OFF.

    • Disconnect and inspect all the PCM connectors.

    • Repair:

      • corrosion (install new connectors or terminals - clean module pins)
      • damaged or bent pins - install new terminals pins
      • pushed-out pins - install new pins as necessary

    • Reconnect the PCM connectors. Make sure they seat and latch correctly.

    • Operate the system and determine if the concern is still present.

    Is the concern still present? 

    Yes  CHECK OASIS for any applicable service articles: TSB, GSB, SSM or FSA. If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions. If no service articles address this concern, INSTALL a new PCM. Refer to POWERTRAIN CONTROL MODULE (PCM) - 2.3L EcoBoost (199kW 270PS) , or refer to POWERTRAIN CONTROL MODULE (PCM) - 2.7L EcoBoost (238kW 324PS) , or refer to POWERTRAIN CONTROL MODULE (PCM) - 3.0L EcoBoost (299kW 406PS) (DD) .
    No  The system is operating correctly at this time. The concern may have been caused by module connections. ADDRESS the root cause of any connector or pin issues.
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