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Home >> Mazda >> 2021 >> CX-3 AWD >> Repair and Diagnosis >> Accessories & Equipment >> Communication Devices >> On-Board Diagnostic - Body Control Module >> DTC U0231-68: Communication Error With Auto Light Sensor/Humidity Sensor/Rain Sensor (BCM) >> Diagnostic Procedure
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Diagnostic Procedure

DTC U0231:68 (BCM) DIAGNOSTIC PROCEDURE

Step Inspection Action
1 VERIFY BCM DTCs AGAIN
  • Clear the DTC for the BCM using the M-MDS. (See CLEARING DTC (BCM) .)
  • Operate the light switch to the AUTO position.
  • Operate the wiper and washer switch to the AUTO position.
  • Switch the ignition ON (engine off or on) and wait for 5 s or more.
  • Retrieve the BCM DTCs using the M-MDS. (See DTC INSPECTION (BCM) .)
  • 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 cable. (See NEGATIVE BATTERY CABLE 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 BCM CONNECTOR CONDITION
  • Disconnect the BCM 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 AUTO LIGHT SENSOR/HUMIDITY SENSOR/RAIN SENSOR CIRCUIT FOR SHORT TO GROUND
  • Verify that the auto light sensor/humidity sensor/rain sensor and BCM connectors are disconnected.
  • Inspect for continuity between BCM terminal 3X (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 the following terminals:
  • Auto light sensor/humidity sensor/rain sensor terminal A-BCM terminal 3X (VIN: Except JM1 DK*****# 300001-)
  • Auto light sensor/humidity sensor/rain sensor terminal C-BCM terminal 3X (VIN: JM1 DK*****# 300001-)

    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 AUTO LIGHT SENSOR/HUMIDITY SENSOR/RAIN SENSOR CIRCUIT FOR SHORT TO POWER SUPPLY
  • Verify that the auto light sensor/humidity sensor/rain sensor and BCM connectors are disconnected.
  • Connect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION .)
  • Switch the ignition ON (engine off or on).
  • Measure the voltage at the BCM terminal 3X (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 the following terminals:
  • Auto light sensor/humidity sensor/rain sensor terminal A-BCM terminal 3X (VIN: Except JM1 DK*****# 300001-)
  • Auto light sensor/humidity sensor/rain sensor terminal C-BCM terminal 3X (VIN: JM1 DK*****# 300001-)

    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 AUTO LIGHT SENSOR/HUMIDITY SENSOR/RAIN SENSOR CIRCUIT FOR OPEN CIRCUIT
  • Switch the ignition off.
  • Disconnect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION .)
  • Verify that the auto light sensor/humidity sensor/rain sensor and BCM connectors are disconnected.
  • Inspect for continuity between the following terminals (wiring harness-side):
    • Auto light sensor/humidity sensor/rain sensor terminal A-BCM terminal 3X (VIN: Except JM1 DK*****# 300001-)
      • Auto light sensor/humidity sensor/rain sensor terminal C-BCM terminal 3X (VIN: JM1 DK*****# 300001-)
  • 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 the following terminals:
  • Auto light sensor/humidity sensor/rain sensor terminal A-BCM terminal 3X (VIN: Except JM1 DK*****# 300001-)
  • Auto light sensor/humidity sensor/rain sensor terminal C-BCM terminal 3X (VIN: JM1 DK*****# 300001-)

    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 VERIFY IF MALFUNCTIONING LOCATION IS AUTO LIGHT SENSOR/HUMIDITY SENSOR/RAIN SENSOR DEPENDING ON REPEATABILITY
  • Always reconnect all disconnected connectors.
  • Connect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION .)
  • Clear the DTC for the BCM using the M-MDS. (See CLEARING DTC (BCM) .)
  • Operate the light switch to the AUTO position.
  • Operate the wiper and washer switch to the AUTO position.
  • Switch the ignition ON (engine off or on) and wait for 5 s or more.
  • Retrieve the BCM DTCs using the M-MDS. (See DTC INSPECTION (BCM) .)
  • 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.
  • Connect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION .)
  • Clear the DTC for the BCM using the M-MDS. (See CLEARING DTC (BCM) .)
  • Operate the light switch to the AUTO position.
  • Operate the wiper and washer switch to the AUTO position.
  • Switch the ignition ON (engine off or on) and wait for 5 s or more.
  • Retrieve the BCM DTCs using the M-MDS. (See DTC INSPECTION (BCM) .)
  • 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 (BCM) .)
No DTC troubleshooting completed.