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Free to use workshop manual for your 2015+ Mk4 'ND' Mazda MX-5
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DTC U3004:12 [START STOP UNIT]

Description

ACC relay circuit malfunction

Detection condition

  • Start stop unit detects that the ACC relay output monitor voltage of 2.5 V or more for 0.5 s or more with the ignition switched off.

Fail-safe

Not applicable.

Possible cause

  • ACC relay malfunction

  • Start stop unit connector or terminal malfunction

  • Short to power supply in wiring harness between ACC relay terminal E and start stop unit terminal 2C

  • Start stop unit malfunction

Diagnostic Procedure

Step

Inspection

Action

1

 INSPECT ACC RELAY

Yes

Go to the next step.

No

Replace the ACC relay, then go to Step 4.

(See RELAY LOCATION.)

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 4.

3

 INSPECT ACC RELAY CIRCUIT FOR SHORT TO POWER SUPPLY

  • Always reconnect all disconnected connectors.

  • Connect the negative battery cable.

    (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.)

  • Measure the voltage at the start stop unit terminal 2C (wiring harness-side).

  • Is the voltage 2.5 V or more?

Yes

Refer to the wiring diagram and verify whether or not there is a common connector between ACC relay terminal E and start stop unit terminal 2C.

    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 the next step.

No

Go to the next step.

4

 VERIFY THAT REPAIRS HAVE BEEN COMPLETED

Yes

Repeat the inspection from Step 1.

Go to the next step.

No

Go to the next step.

5

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

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