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DTC U0028:87 [START STOP UNIT]

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2016 – MX-5 – Body and Accessories

DTC U0028:87 [START STOP UNIT]

Description

Communication error with BCM

Detection condition

  • Start stop unit detects the communication error with BCM 10 times continuously.

Fail-safe

  • Performs control with the driver’s side door and trunk open.

Possible cause

  • BCM connector or terminal malfunction

  • Start stop unit connector or terminal malfunction

  • Short to ground in wiring harness between start stop unit terminal 1Q and BCM terminal 2J

  • Open circuit in wiring harness between start stop unit terminal 1Q and BCM terminal 2J

  • BCM malfunction

  • Start stop unit 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 6.

2

INSPECT START STOP UNIT CONNECTOR CONDITION

  • Disconnect the start stop unit 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 6.

3

INSPECT WIRING HARNESS BETWEEN BCM AND START STOP UNIT FOR SHORT TO GROUND

  • Verify that the BCM and start stop unit connectors are disconnected.

  • Inspect for continuity between BCM terminal 2J (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 start stop unit terminal 1Q and BCM terminal 2J.

    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 6.

No

Go to the next step.

4

INSPECT WIRING HARNESS BETWEEN BCM AND START STOP UNIT FOR OPEN CIRCUIT

  • Verify that the BCM and start stop unit connectors are disconnected.

  • Inspect for continuity between start stop unit terminal 1Q (wiring harness-side) and BCM terminal 2J (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 start stop unit terminal 1Q and BCM terminal 2J.

    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 6.

5

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 7.

6

VERIFY THAT REPAIRS HAVE BEEN COMPLETED

Yes

Repeat the inspection from Step 1.

Go to the next step.

No

Go to the next step.

7

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 [START STOP UNIT].)

No

DTC troubleshooting completed.

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