501-20B Supplemental Restraint System 2014 Fiesta
Diagnosis and Testing Procedure revision date: 05/6/2013

Pinpoint Test - DTC: Z

U0028:08 and U0028:88


Refer to Wiring Diagrams Cell 46 for schematic and connector information.

Normal Operation and Fault Conditions

The RCM supplies the stability/traction control system with the yaw rate, roll rate, lateral and longitudinal accelerometer over a dedicated CAN bus. If the RCM detects a fault with communications with the ABS module or dedicated CAN bus circuits, it sets DTC U0028:08 or U0028:88.

The RCM does not request the IPC module to illuminate the airbag warning indicator if either DTC U0028:08 or U0028:88 is set.



  DTC Fault Trigger Conditions


  DTC Description Fault Trigger Conditions
U0028:08 Vehicle Communication Bus A: Bus Signal / Message Failures A fault is indicated when the RCM does not receive messages from the ABS module on the dedicated CAN bus for 5 seconds. An open dedicated CAN circuit, incorrectly installed ABS module or loss of power and/or ground to the ABS module can set this DTC .
U0028:88 Vehicle Communication Bus A: Bus Off A fault is indicated when the RCM detects the dedicated CAN circuits are shorted to ground, shorted to voltage or shorted to each other.


Possible Causes

Visual Inspection and Diagnostic Pre-checks


PINPOINT TEST A : U0028:08 AND U0028:88
NOTE: Most faults are due to connector and/or wiring concerns. Carry out a thorough inspection and verification before proceeding with the pinpoint test.
NOTE: Only disconnect or reconnect SRS components when instructed to do so within a pinpoint test step. Failure to follow this instruction may result in incorrect diagnosis of the SRS .
NOTE: Always make sure the correct SRS component is being installed. Parts released for other vehicles may not be compatible even if they appear physically similar. Check the part number listed in the Ford parts catalog to make sure the correct component is being installed. If an incorrect SRS component is installed, Diagnostic Trouble Codes (DTCs) may set.
NOTE: The SRS must be fully operational and free of faults before releasing the vehicle to the customer.
A1   RETRIEVE RCM (RESTRAINTS CONTROL MODULE) DIAGNOSTIC TROUBLE CODES (DTCS)
  • Ignition ON.
  • Using a diagnostic scan tool, perform RCM self-test.

Was DTC U0028:08 or U0028:88 retrieved on-demand during self-test?

Yes This fault cannot be cleared until it is corrected and the DTC is no longer retrieved on-demand during self-test.
For DTC U0028:08, GO to A2
For DTC U0028:88, GO to A5
No This is an intermittent fault when present as a Continuous Memory Diagnostic Trouble Code (CMDTC) only. GO to A13


A2   VERIFY THE RCM (RESTRAINTS CONTROL MODULE) PART NUMBER
  • Using the Log Viewer function of the diagnostic scan tool, retrieve and record the RCM part number.
  • Check the part number recorded against the number listed in the parts catalog and verify the correct RCM is present in the vehicle.

Is the correct RCM installed?

Yes GO to A3
No INSTALL the correct RCM .
REFER to: Restraints Control Module (RCM) (501-20B Supplemental Restraint System, Removal and Installation).
GO to A14


A3   VERIFY THE ABS (ANTI-LOCK BRAKE SYSTEM) MODULE PART NUMBER
  • Using the Log Viewer function of the diagnostic scan tool, retrieve and record the ABS module part number.
  • Check the part number recorded against the number listed in the parts catalog and verify the correct ABS module is present in the vehicle.

Is the correct ABS module installed?

Yes GO to A4
No INSTALL the correct ABS module.
REFER to: Hydraulic Control Unit (HCU) (206-09 Anti-Lock Brake System (ABS) and Stability Control, Removal and Installation).
GO to A14


A4   CHECK THE HS-CAN (HIGH SPEED-CONTROLLER AREA NETWORK) COMMUNICATIONS ( ABS (ANTI-LOCK BRAKE SYSTEM) MODULE COMMUNICATIONS)
  • NOTE: The Network Test does not test the dedicated CAN communications between the ABS module and RCM .

    Using a diagnostic scan tool, perform a Network Test.

Did the Network Test pass ( ABS module communicates with the scan tool)?

Yes GO to A5
No DIAGNOSE the HS-CAN / ABS module communication concern.
REFER to: Communications Network (418-00 Module Communications Network, Diagnosis and Testing).
GO to A14


A5   CHECK THE DEDICATED CAN (CONTROLLER AREA NETWORK) CIRCUITS FOR AN OPEN
  • Ignition OFF.
  • Disconnect: RCM C310A and C310B.
  • Disconnect: ABS module C135.
  • Measure:


    Positive Lead Measurement / Action Negative Lead
      C310B-60   C135-32
      C310B-59   C135-33



Are the resistances less than 5 ohms?

Yes For DTC U0028:08, GO to A9
For DTC U0028:88, GO to A6
No REPAIR the affected circuit.
Refer to Wiring Diagrams Cell 5 for schematic and connector information.
GO to A14


A6   CHECK THE DEDICATED CAN (CONTROLLER AREA NETWORK) CIRCUITS FOR A SHORT TO VOLTAGE
  • Ignition ON.
  • Measure:


    Positive Lead Measurement / Action Negative Lead
      C135-32   Ground
      C135-33   Ground



Is voltage present on either circuit?

Yes REPAIR the affected circuit(s).
Refer to Wiring Diagrams Cell 5 for schematic and connector information.
GO to A14
No GO to A7


A7   CHECK THE DEDICATED CAN (CONTROLLER AREA NETWORK) CIRCUITS FOR A SHORT TO GROUND
  • Ignition OFF.
  • Measure:


    Positive Lead Measurement / Action Negative Lead
      C135-32   Ground
      C135-33   Ground



Are the resistances greater than 10,000 ohms?

Yes GO to A8
No REPAIR the affected circuit(s).
Refer to Wiring Diagrams Cell 5 for schematic and connector information.
GO to A14


A8   CHECK FOR A SHORT BETWEEN THE DEDICATED CAN (CONTROLLER AREA NETWORK) CIRCUITS
  • Measure:


    Positive Lead Measurement / Action Negative Lead
      C135-32   C135-33



Is the resistance greater than 10,000 ohms?

Yes GO to A9
No REPAIR the circuit(s).
Refer to Wiring Diagrams Cell 5 for schematic and connector information.
GO to A14


A9   CHECK THE RCM (RESTRAINTS CONTROL MODULE) TERMINATING RESISTOR
  • Connect: RCM C310B.
  • Measure:


    Positive Lead Measurement / Action Negative Lead
      C135-32   C135-33



Is the resistance between 108 and 132 ohms?

Yes GO to A10
No GO to A11


A10   CHECK THE ABS (ANTI-LOCK BRAKE SYSTEM) MODULE TERMINATING RESISTOR
  • Disconnect: RCM C310B.
  • Connect: ABS module C135.
  • Measure:


    Positive Lead Measurement / Action Negative Lead
      C310B-59   C310B-60



Is the resistance between 108 and 132 ohms?

Yes For DTC U0028:08, GO to A11
For DTC U0028:88, GO to A12
No GO to A12


A11   CONFIRM THE RCM (RESTRAINTS CONTROL MODULE) FAULT

NOTE: Make sure all SRS components and the RCM electrical connectors are connected before carrying out the self-test. If not, Diagnostic Trouble Codes (DTCs) will be recorded.

  • Prior to reconnecting any previously disconnected SRS component:
    • inspect connector(s) (including any inline connectors) for pushed-out, loose or spread terminals and loose or frayed wire connections at terminals.
    • inspect wire harness for any damaged, pinched, cut or pierced wires.
    • inspect RCM C310A and C310B Connector Position Assurance (CPA) lever/lock for correct operation.
    • inspect ABS module C135 for dirt, corrosion, water intrusion, pushed-out, loose or spread terminals and loose or frayed wire connections at terminals.
    • repair any concerns found.
      Refer to Wiring Diagrams Cell 5 for schematic and connector information.
  • Connect: ABS module C135.
  • Connect: RCM C310A and C310B.
  • Ignition ON.
  • Using a diagnostic scan tool, perform RCM self-test.

Was the original DTC retrieved on-demand during self-test?

Yes CHECK OASIS for any applicable Technical Service Bulletins (TSBs). If a TSB exists for this concern, DISCONTINUE this test and FOLLOW TSB instructions. If no Technical Service Bulletins (TSBs) address this concern, INSTALL a new RCM .
REFER to: Restraints Control Module (RCM) (501-20B Supplemental Restraint System, Removal and Installation).
GO to A14
No In the process of diagnosing the fault, the fault condition has become intermittent. Do not install any new SRS components at this time. Install SRS components only when directed to do so in the pinpoint test. GO to A13


A12   CONFIRM THE ABS (ANTI-LOCK BRAKE SYSTEM) MODULE FAULT

NOTE: Make sure all SRS components and the RCM electrical connectors are connected before carrying out the self-test. If not, Diagnostic Trouble Codes (DTCs) will be recorded.

  • Prior to reconnecting any previously disconnected SRS component:
    • inspect connector(s) (including any inline connectors) for pushed-out, loose or spread terminals and loose or frayed wire connections at terminals.
    • inspect wire harness for any damaged, pinched, cut or pierced wires.
    • inspect RCM C310A and C310B Connector Position Assurance (CPA) lever/lock for correct operation.
    • inspect ABS module C135 for dirt, corrosion, water intrusion, pushed-out, loose or spread terminals and loose or frayed wire connections at terminals.
    • repair any concerns found.
      Refer to Wiring Diagrams Cell 5 for schematic and connector information.
  • Connect: ABS module C135.
  • Connect: RCM C310A and C310B.
  • Ignition ON.
  • Using a diagnostic scan tool, perform RCM self-test.

Was the original DTC retrieved on-demand during self-test?

Yes CHECK OASIS for any applicable Technical Service Bulletins (TSBs). If a TSB exists for this concern, DISCONTINUE this test and FOLLOW TSB instructions. If no Technical Service Bulletins (TSBs) address this concern, INSTALL a new ABS module.
REFER to: Hydraulic Control Unit (HCU) (206-09 Anti-Lock Brake System (ABS) and Stability Control, Removal and Installation).
GO to A14
No In the process of diagnosing the fault, the fault condition has become intermittent. Do not install any new SRS components at this time. Install SRS components only when directed to do so in the pinpoint test. GO to A13


A13   CHECK FOR AN INTERMITTENT FAULT
  • Ignition OFF.
  • Disconnect: ABS module C135.
  • Disconnect: RCM C310A and C310B.
    • inspect connector(s) (including any inline connectors) for pushed-out, loose or spread terminals and loose or frayed wire connections at terminals.
    • inspect wire harness for any damaged, pinched, cut or pierced wires.
    • inspect RCM C310A and C310B Connector Position Assurance (CPA) lever/lock for correct operation.
    • inspect ABS module C135 for dirt, corrosion, water intrusion, pushed-out, loose or spread terminals and loose or frayed wire connections at terminals.
    • repair any concerns found.
      Refer to Wiring Diagrams Cell 5 for schematic and connector information.
  • Connect: ABS module C135.
  • Connect: RCM C310A and C310B.
  • Ignition ON.
  • Using a diagnostic scan tool, perform RCM self-test.

Was DTC U0028:08 or U0028:88 retrieved on-demand during self-test?

Yes This fault cannot be cleared until it is corrected and the DTC is no longer retrieved on-demand during self-test. CHECK for causes of the intermittent fault in the areas previously worked in, particularly the pins and terminals of any electrical connector that were disconnected. REPAIR any intermittent wiring, terminal or connector concerns found.
Refer to Wiring Diagrams Cell 5 for schematic and connector information.
GO to A14
No The fault is not present and cannot be recreated at this time. Do not install any new SRS components at this time. Install SRS components only when directed to do so in the pinpoint test. GO to A14


A14   CHECK FOR ADDITIONAL SRS (SUPPLEMENTAL RESTRAINT SYSTEM) DIAGNOSTIC TROUBLE CODES (DTCS)

WARNING: Turn the ignition OFF and wait one minute to deplete the backup power supply. Failure to follow this instruction may result in serious personal injury or death in the event of an accidental deployment.

  • Ignition OFF.
  • Connect: ABS module C135 (if previously disconnected).
  • Connect: RCM C310A and C310B (if previously disconnected).
  • Ignition ON.
  • Using a diagnostic scan tool, perform RCM self-test.
  • Using a diagnostic scan tool, perform ABS module self-test.

Are any RCM and/or ABS module Diagnostic Trouble Codes (DTCs) retrieved on-demand during self-test?

Yes Do not clear any Diagnostic Trouble Codes (DTCs) until all Diagnostic Trouble Codes (DTCs) have been resolved. For RCM Diagnostic Trouble Codes (DTCs),
REFER to: Airbag Supplemental Restraint System (SRS) (501-20B Supplemental Restraint System, Diagnosis and Testing).
For ABS module Diagnostic Trouble Codes (DTCs),
REFER to: Anti-Lock Brake System (ABS) and Stability Control (206-09 Anti-Lock Brake System (ABS) and Stability Control, Diagnosis and Testing).
No CLEAR Continuous Memory Diagnostic Trouble Codes (CMDTCs) in all modules. PROVE OUT the SRS . The repair is complete. RETURN the vehicle to the customer.





Copyright © Ford Motor Company