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DTC B1142:13 [ELECTRICAL SUPPLY UNIT (ESU)]

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2016 – MX-5 – Body and Accessories

DTC B1142:13 [ELECTRICAL SUPPLY UNIT (ESU)]

Description

Ignition switch status mismatch

Detection condition

  • The electrical supply unit (ESU) detects the following mismatches.

    • Ignition switch status determined from power supply condition in BCM received from BCM via LIN communication

    • Ignition switch status determined from power supply input condition of electrical supply unit (ESU) power supply circuit (IG1)

Fail-safe

Not applicable

Possible cause

  • BCM connector or terminal malfunction

  • Electrical supply unit (ESU) connector or terminal malfunction

  • BCM power supply circuit (IG1) malfunction

    • Short to ground in the wiring harness between METER1 10 A fuse and BCM terminal 3O

    • METER1 10 A fuse malfunction

    • Open circuit in wiring harness between IG1 relay terminal C and BCM terminal 3O

  • Electrical supply unit (ESU) power supply circuit (IG1) malfunction

    • Short to ground in the wiring harness between METER1 10 A fuse and electrical supply unit (ESU) terminal 1H

    • METER1 10 A fuse malfunction

    • Open circuit in wiring harness between IG1 relay terminal C and electrical supply unit (ESU) terminal 1H

  • Short to ground in wiring harness between BCM terminal 2Y and electrical supply unit (ESU) terminal 2I

  • Short to power supply in wiring harness between BCM terminal 2Y and electrical supply unit (ESU) terminal 2I

  • Open circuit in wiring harness between BCM terminal 2Y and electrical supply unit (ESU) terminal 2I

  • BCM malfunction

  • Electrical supply unit (ESU) malfunction

Diagnostic Procedure

Step

Inspection

Action

1

 INSPECT BCM CONNECTOR CONDITION

  • Switch the ignition off.

  • Disconnect the negative battery cable.

    (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.)

  • 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 9.

2

 INSPECT ELECTRICAL SUPPLY UNIT (ESU) CONNECTOR CONDITION

  • Disconnect the electrical supply unit (ESU) 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 9.

3

 VERIFY BCM POWER SUPPLY (IG1) VOLTAGE

Yes

Go to the next step.

No

Inspect the METER1 10 A fuse.

  • If the fuse is blown:

    • Refer to the wiring diagram and verify whether or not there is a common connector between METER1 10 A fuse and BCM terminal 3O.

        • 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.

      • Replace the fuse.

  • If the fuse is damaged:

    • Replace the fuse.

  • If the fuse is normal:

    • Refer to the wiring diagram and verify whether or not there is a common connector between IG1 relay terminal C and BCM terminal 3O.

        • 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 9.

4

 VERIFY ELECTRICAL SUPPLY UNIT (ESU) POWER SUPPLY (IG1) VOLTAGE

  • Measure the voltage at the electrical supply unit (ESU) terminal 1H (wiring harness-side).

  • Is the voltage B+?

Yes

Go to the next step.

No

Inspect the METER1 10 A fuse.

  • If the fuse is blown:

    • Refer to the wiring diagram and verify whether or not there is a common connector between METER1 10 A fuse and electrical supply unit (ESU) terminal 1H.

        • 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.

      • Replace the fuse.

  • If the fuse is damaged:

    • Replace the fuse.

  • If the fuse is normal:

    • Refer to the wiring diagram and verify whether or not there is a common connector between IG1 relay terminal C and electrical supply unit (ESU) terminal 1H.

        • 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 9.

5

 INSPECT LIN COMMUNICATION CIRCUIT BETWEEN BCM AND ELECTRICAL SUPPLY UNIT (ESU) FOR SHORT TO GROUND

  • Switch the ignition off.

  • Disconnect the negative battery cable.

    (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.)

  • Verify that the BCM and electrical supply unit (ESU) connectors are disconnected.

  • Inspect for continuity between BCM terminal 2Y (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 BCM terminal 2Y and electrical supply unit (ESU) terminal 2I.

    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 9.

No

Go to the next step.

6

 INSPECT LIN COMMUNICATION CIRCUIT BETWEEN BCM AND ELECTRICAL SUPPLY UNIT (ESU) FOR SHORT TO POWER SUPPLY

  • Verify that the BCM and electrical supply unit (ESU) 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 2Y (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 BCM terminal 2Y and electrical supply unit (ESU) terminal 2I.

    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 9.

7

 INSPECT LIN COMMUNICATION CIRCUIT BETWEEN BCM AND ELECTRICAL SUPPLY UNIT (ESU) FOR OPEN CIRCUIT

  • Switch the ignition off.

  • Disconnect the negative battery cable.

    (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.)

  • Verify that the BCM and electrical supply unit (ESU) connectors are disconnected.

  • Inspect the wiring harness for continuity between BCM terminal 2Y (wiring harness-side) and electrical supply unit (ESU) terminal 2I (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 BCM terminal 2Y and electrical supply unit (ESU) terminal 2I.

    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 9.

8

 VERIFY IF MALFUNCTIONING LOCATION IS BCM DEPENDING ON REPEATABILITY

Yes

Replace the BCM, then go to the next step.

(See BODY CONTROL MODULE (BCM) REMOVAL/INSTALLATION.)

No

Go to Step 10.

9

 VERIFY THAT REPAIRS HAVE BEEN COMPLETED

Yes

Repeat the inspection from Step 1.

Go to the next step.

No

Go to the next step.

10

 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 [ELECTRICAL SUPPLY UNIT (ESU)].)

No

DTC troubleshooting completed.

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