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DTC B1098:11 [ELECTRICAL SUPPLY UNIT (ESU)]

Description

Parking light (LH), front side marker light (LH), taillight (RH) or rear side marker light (RH) circuit malfunction

Detection condition

  • The electrical supply unit (ESU) detects a short to ground in the parking light (LH), front side marker light (LH), taillight (RH) or rear side marker light (RH) circuit.

Fail-safe

Not applicable

Possible cause

  • Electrical supply unit (ESU) connector or terminal malfunction

  • Front side marker light bulb (LH) malfunction

  • Front side marker light (LH) connector or terminal malfunction

  • Front combination light (LH) connector or terminal malfunction

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

    • Front combination light (LH) terminal D—Electrical supply unit (ESU) terminal 4I

    • Front side marker light (LH) terminal A—Electrical supply unit (ESU) terminal 4I

  • Front combination light (LH) malfunction

  • Rear side marker light bulb (RH) malfunction

  • Rear side marker light (RH) connector or terminal malfunction

  • Rear combination light (RH) connector or terminal malfunction

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

    • Rear combination light (RH) terminal C—Electrical supply unit (ESU) terminal 2A

    • Rear side marker light (RH) terminal A—Electrical supply unit (ESU) terminal 2A

  • Rear combination light (RH) malfunction

  • Electrical supply unit (ESU) malfunction

Diagnostic Procedure

Step

Inspection

Action

1

 DETERMINE MALFUNCTIONING LIGHT

  • Operate the light switch to the TNS (parking lights) position.

  • Are there any lights among the following which are not illuminated?

    • Parking light (LH)

    • Front side marker light (LH)

    • Taillight (RH)

    • Rear side marker light (RH)

Yes

If all lights do not turn on:

  • Go to the next step.

If parking light (LH) and front side marker light (LH) does not turn on:

  • Go to Step 3.

If taillight (RH) and rear side marker light (RH) does not turn on:

  • Go to Step 9.

No

Go to Step 15.

2

 INSPECT ELECTRICAL SUPPLY UNIT (ESU) CONNECTOR CONDITION

  • Switch the ignition off.

  • Disconnect the negative battery cable.

    (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.)

  • 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 Step 15.

No

Repair or replace the connector, then go to Step 15.

3

 VISUALLY INSPECT FRONT SIDE MARKER LIGHT BULB (LH)

  • Visually inspect the front side marker light bulb (LH).

  • Is the front side marker light bulb (LH) normal?

Yes

Go to the next step.

No

Replace the front side marker light bulb (LH), then go to Step 15.

(See FRONT SIDE MARKER LIGHT BULB REMOVAL/INSTALLATION.)

4

 INSPECT FRONT SIDE MARKER LIGHT (LH) CONNECTOR CONDITION

  • Switch the ignition off.

  • Disconnect the negative battery cable.

    (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.)

  • Disconnect front side marker 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 15.

5

 INSPECT FRONT COMBINATION LIGHT (LH) CONNECTOR CONDITION

  • Disconnect the front combination 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 15.

6

 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 15.

7

 INSPECT PARKING LIGHT (LH) AND FRONT SIDE MARKER LIGHT (LH) CONTROL CIRCUIT FOR SHORT TO GROUND

  • Verify that the front side marker light (LH), front combination light (LH) and electrical supply unit (ESU) connectors are disconnected.

  • Inspect for continuity between the following terminals (wiring harness-side) and body ground:

    • Front combination light (LH) terminal D

    • Front side marker light (LH) terminal A

  • Is there continuity?

Yes

Refer to the wiring diagram and verify whether or not there is a common connector between following terminals:

  • Front combination light (LH) terminal D—Electrical supply unit (ESU) terminal 4I

  • Front side marker light (LH) terminal A—Electrical supply unit (ESU) terminal 4I

    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 15.

No

Go to the next step.

8

 VERIFY IF MALFUNCTIONING LOCATION IS FRONT COMBINATION LIGHT (LH) DEPENDING ON REPEATABILITY

Yes

Replace the front combination light (LH), then go to Step 15.

(See FRONT COMBINATION LIGHT REMOVAL/INSTALLATION.)

No

Go to Step 16.

9

 VISUALLY INSPECT REAR SIDE MARKER LIGHT BULB (RH)

  • Visually inspect the rear side marker light bulb (RH).

  • Is the rear side marker light bulb (RH) normal?

Yes

Go to the next step.

No

Replace the rear side marker light bulb (RH), then go to Step 15.

(See REAR SIDE MARKER LIGHT BULB REMOVAL/INSTALLATION.)

10

 INSPECT REAR SIDE MARKER LIGHT (RH) CONNECTOR CONDITION

  • Switch the ignition off.

  • Disconnect the negative battery cable.

    (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.)

  • Disconnect rear side marker 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 15.

11

 INSPECT REAR COMBINATION LIGHT (RH) CONNECTOR CONDITION

  • Disconnect the rear combination 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 15.

12

 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 15.

13

 INSPECT TAILLIGHT (RH) AND REAR SIDE MARKER LIGHT (RH) CONTROL CIRCUIT FOR SHORT TO GROUND

  • Verify that the rear side marker light (RH), rear combination light (RH) and electrical supply unit (ESU) connectors are disconnected.

  • Inspect for continuity between the following terminals (wiring harness-side) and body ground:

    • Rear combination light (RH) terminal C

    • Rear side marker light (RH) terminal A

  • Is there continuity?

Yes

Refer to the wiring diagram and verify whether or not there is a common connector between following terminals:

  • Rear combination light (RH) terminal C—Electrical supply unit (ESU) terminal 2A

  • Rear side marker light (RH) terminal A—Electrical supply unit (ESU) terminal 2A

    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 15.

No

Go to the next step.

14

 VERIFY IF MALFUNCTIONING LOCATION IS REAR COMBINATION LIGHT (RH) DEPENDING ON REPEATABILITY

Yes

Replace the rear combination light (RH), then go to the next step.

(See REAR COMBINATION LIGHT REMOVAL/INSTALLATION.)

No

Go to Step 16.

15

 VERIFY THAT REPAIRS HAVE BEEN COMPLETED

Yes

Repeat the inspection from Step 1.

Go to the next step.

No

Go to the next step.

16

 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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Free to use workshop manual for your 2015+ Mk4 'ND' Mazda MX-5

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