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DTC B1277:11 [ELECTRICAL SUPPLY UNIT (ESU)]

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2016 – MX-5 – Body and Accessories

DTC B1277:11 [ELECTRICAL SUPPLY UNIT (ESU)]

Description

Back-up light circuit malfunction

Detection condition

  • Electrical supply unit (ESU) detects a short to ground in the back-up light circuit with the ignition switched ON (engine off or on).

Fail-safe

Not applicable

Possible cause

  • Back-up light bulb (LH) malfunction

  • Back-up light bulb (RH) malfunction

  • Back-up light (LH) connector or terminal malfunction

  • Back-up light (RH) connector or terminal malfunction

  • Electrical supply unit (ESU) connector or terminal malfunction

  • Short to ground in wiring harness between the following terminals:

    • Electrical supply unit (ESU) terminal 2Q—Back-up light (LH) terminal A

    • Electrical supply unit (ESU) terminal 2Q—Back-up light (RH) terminal A

  • Electrical supply unit (ESU) malfunction

Diagnostic Procedure

Step

Inspection

Action

1

VISUALLY INSPECT BACK-UP LIGHT BULB (LH)

  • Visually inspect the back-up light bulb (LH).

  • Is the back-up light bulb (LH) normal?

Yes

Go to the next step.

No

Replace the back-up light bulb (LH), then go to Step 7.

(See BACK-UP LIGHT BULB REMOVAL/INSTALLATION.)

2

VISUALLY INSPECT BACK-UP LIGHT BULB (RH)

  • Visually inspect the back-up light bulb (RH).

  • Is the back-up light (RH) normal?

Yes

Go to the next step.

No

Replace the back-up light bulb (RH), then go to Step 7.

(See BACK-UP LIGHT BULB REMOVAL/INSTALLATION.)

3

INSPECT BACK-UP LIGHT (LH) CONNECTOR CONDITION

  • Switch the ignition off.

  • Disconnect the negative battery cable.

    (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.)

  • Disconnect the back-up light (LH) 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 7.

4

INSPECT BACK-UP LIGHT (RH) CONNECTOR CONDITION

  • Disconnect the back-up light (RH) 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 7.

5

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 7.

6

INSPECT BACK-UP LIGHT CONTROL CIRCUIT FOR SHORT TO GROUND

  • Verify that the back-up light (LH)/(RH) and electrical supply unit (ESU) connectors are disconnected.

  • Inspect for continuity between electrical supply unit (ESU) terminal 2Q (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:

  • Electrical supply unit (ESU) terminal 2Q—Back-up light (LH) terminal A

  • Electrical supply unit (ESU) terminal 2Q—Back-up light (RH) terminal A

    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 the next step.

No

Go to the next step.

7

VERIFY THAT REPAIRS HAVE BEEN COMPLETED

Yes

Repeat the inspection from Step 1.

Go to the next step.

No

Go to the next step.

8

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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