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Diagnostic Procedure

WARNING: This page is about a different car, the 2014 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.
DTC U0231:68 (FRONT BODY CONTROL MODULE) DIAGNOSTIC PROCEDURE

Step Inspection Action
1 VERIFY FRONT BODY CONTROL MODULE (FBCM) DTCs AGAIN 
 Yes Go to the next step.
No Go to Step 9.
2 INSPECT AUTO LIGHT SENSOR/RAIN SENSOR CONNECTOR 
  • Switch the ignition off.
  • Disconnect the negative battery cable.

    (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-G 2.5] .)

  • Disconnect the auto light sensor/rain sensor connector.
  • Inspect the connector engagement and connection condition and inspect the terminals for damage, deformation, corrosion, or disconnection.
  • Is the connector normal?
 Yes Go to the next step.
No Repair or replace the connector, then go to Step 8.
3 INSPECT FRONT BODY CONTROL MODULE (FBCM) CONNECTOR 
  • Disconnect the front body control module (FBCM) connector.
  • Inspect the connector engagement and connection condition and inspect the terminals for damage, deformation, corrosion, or disconnection.
  • Is the connector normal?
 Yes Go to the next step.
No Repair or replace the connector, then go to Step 8.
4 INSPECT FOR SHORT TO GROUND IN AUTO LIGHT SENSOR/RAIN SENSOR CIRCUIT 
  • Verify that the auto light sensor/rain sensor and front body control module (FBCM) connectors are disconnected.
  • Inspect for continuity between front body control module (FBCM) terminal 2G (wiring harness-side) and body ground.
  • Is there continuity?
 Yes Refer to the wiring diagram and verify whether or not there is a common connector between auto light sensor/rain sensor terminal A and front body control module (FBCM) terminal 2G.
If there is a common connector: 
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a short to ground.
  • Repair or replace the malfunctioning part.

If there is no common connector: 
  • Repair or replace the wiring harness which has a short to ground.

Go to Step 8.
No Go to the next step.
5 INSPECT FOR SHORT TO POWER SUPPLY IN AUTO LIGHT SENSOR/RAIN SENSOR CIRCUIT 
  • Verify that the auto light sensor/rain sensor and front body control module (FBCM) connectors are disconnected.
  • Reconnect the negative battery cable.

    (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-G 2.5] .)

  • Switch the ignition ON (engine off or on).
  • Measure the voltage at the front body control module (FBCM) terminal 2G (wiring harness-side).
  • Is the voltage 0 V  ?
 Yes Go to the next step.
No Refer to the wiring diagram and verify whether or not there is a common connector between auto light sensor/rain sensor terminal A and front body control module (FBCM) terminal 2G.
If there is a common connector: 
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a short to power supply.
  • Repair or replace the malfunctioning part.

If there is no common connector: 
  • Repair or replace the wiring harness which has a short to power supply.

Go to Step 8.
6 INSPECT FOR OPEN CIRCUIT IN AUTO LIGHT SENSOR/RAIN SENSOR CIRCUIT 
  • Verify that the auto light sensor/rain sensor and front body control module (FBCM) connectors are disconnected.
  • Switch the ignition off.
  • Disconnect the negative battery cable.

    (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-G 2.5] .)

  • Inspect the wiring harness for continuity between auto light sensor/rain sensor terminal A (wiring harness-side) and front body control module (FBCM) terminal 2G (wiring harness-side).
  • Is there continuity?
 Yes Go to the next step.
No Refer to the wiring diagram and verify whether or not there is a common connector between auto light sensor/rain sensor terminal A and front body control module (FBCM) terminal 2G.
If there is a common connector: 
  • Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit.
  • Repair or replace the malfunctioning part.

If there is no common connector: 
  • Repair or replace the wiring harness which has an open circuit.

Go to Step 8.
7 PERFORM DTC INSPECTION AND VERIFY AUTO LIGHT SENSOR/RAIN SENSOR MALFUNCTION 
 Yes Replace the auto light sensor/rain sensor, then go to the next step.
(See RAIN SENSOR REMOVAL/INSTALLATION .)
No Go to Step 9.
8 VERIFY THAT REPAIRS HAVE BEEN COMPLETED 
 Yes Repeat the inspection from Step 1.

Go to the next step.
No Go to the next step.
9 VERIFY IF OTHER DTCs DISPLAYED 
  • Are any other DTCs displayed?
 Yes Repair or replace the malfunctioning part according to the applicable DTC troubleshooting.
(See DTC TABLE [FRONT BODY CONTROL MODULE (FBCM)] .)
No DTC troubleshooting completed.
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