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Home >> Mazda >> 2020 >> CX-5 Signature >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Communication Devices >> On-Board Diagnostic - Front Body Control Module (FBCM) >> DTC U0231-68: Communication Error With Auto Light Sensor/Humidity Sensor/Rain Sensor >> Diagnostic Procedure
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Diagnostic Procedure

DTC U0231:68 (FRONT BODY CONTROL MODULE) DIAGNOSTIC PROCEDURE

Step Inspection Action
1 VERIFY FRONT BODY CONTROL MODULE (FBCM) DTCs AGAIN
  • Clear the DTC for the front body control module (FBCM) using the M-MDS. (See CLEARING DTC .)
  • Switch the ignition ON (engine off or on) and wait for 5 s or more.
  • Retrieve the front body control module (FBCM) DTCs using the M-MDS. (See DTC INSPECTION .)
  • Is the same DTC displayed?
 Yes Go to the next step.
No Go to Step 9.
2 INSPECT AUTO LIGHT SENSOR/HUMIDITY SENSOR/RAIN SENSOR CONNECTOR CONDITION
  • Switch the ignition off.
  • Disconnect the negative battery terminal. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION .)
  • Disconnect the auto light sensor/humidity 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 CONDITION
  • 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/HUMIDITY SENSOR/RAIN SENSOR CIRCUIT
  • Verify that the auto light sensor/humidity 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/humidity sensor/rain sensor terminal C 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/HUMIDITY SENSOR/RAIN SENSOR CIRCUIT
  • Verify that the auto light sensor/humidity sensor/rain sensor and front body control module (FBCM) connectors are disconnected.
  • Reconnect the negative battery terminal. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION .)
  • 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/humidity sensor/rain sensor terminal C 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/HUMIDITY SENSOR/RAIN SENSOR CIRCUIT
  • Verify that the auto light sensor/humidity sensor/rain sensor and front body control module (FBCM) connectors are disconnected.
  • Switch the ignition off.
  • Disconnect the negative battery terminal. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION .)
  • Inspect the wiring harness for continuity between auto light sensor/humidity sensor/rain sensor terminal C (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/humidity sensor/rain sensor terminal C 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/HUMIDITY SENSOR/RAIN SENSOR MALFUNCTION
  • Always reconnect all disconnected connectors.
  • Reconnect the negative battery terminal. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION .)
  • Clear the DTC for the front body control module (FBCM) using the M-MDS. (See CLEARING DTC .)
  • Switch the ignition ON (engine off or on) and wait for 5 s or more.
  • Retrieve the front body control module (FBCM) DTCs using the M-MDS. (See DTC INSPECTION .)
  • Is the same DTC displayed?
 Yes Replace the auto light sensor/humidity 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
  • Always reconnect all disconnected connectors.
  • Reconnect the negative battery terminal. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION .)
  • Clear the DTC for the front body control module (FBCM) using the M-MDS. (See CLEARING DTC .)
  • Switch the ignition ON (engine off or on) and wait for 5 s or more.
  • Retrieve the front body control module (FBCM) DTCs using the M-MDS. (See DTC INSPECTION .)
  • Is the same DTC displayed?
 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 .)
No DTC troubleshooting completed.
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