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Home >> Mazda >> 2017 >> MX-5 Miata Club, Automatic Trans >> Repair and Diagnosis >> Body & Frame >> Door Locks >> On-Board Diagnostic - Retractable Fastback Control Module >> DTC U0031-86; Communication Error With Power Window Main Switch >> Diagnostic Procedure
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Diagnostic Procedure

Step Inspection Action
1 VERIFY OTHER RETRACTABLE FASTBACK CONTROL MODULE DTCs
Yes Replace the retractable fastback control module, then go to Step 5.
(See RETRACTABLE FASTBACK CONTROL MODULE REMOVAL/INSTALLATION ).
No Go to the next step.
2 POWER WINDOW MAIN SWITCH CIRCUIT FOR SHORT TO GROUND
  • Switch the ignition off.
  • Disconnect the negative battery cable.

    (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION ).

  • Disconnect the retractable fastback control module and power window main switch connectors.
  • Inspect for continuity between the following terminals (wiring harness-side) and body ground:
    • Power window main switch terminal 1J
  • Is there continuity?
Yes Refer to the wiring diagram and verify whether or not there is a common connector between the following terminals:
  • Retractable fastback control module terminal 4AD and power window main switch terminal 1J

    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 5.
No Go to the next step.
3 POWER WINDOW MAIN SWITCH CIRCUIT FOR SHORT TO POWER SUPPLY
  • Verify that the retractable fastback control module and power window main switch 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 following terminals (wiring harness-side):
    • Power window main switch terminal 1J
  • 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 the following terminals:
  • Retractable fastback control module terminal 4AD and power window main switch terminal 1J

    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 5.
4 POWER WINDOW MAIN SWITCH
Yes Go to the next step.
No Replace the power window main switch, then go to the next step.
(See POWER WINDOW MAIN SWITCH REMOVAL/INSTALLATION ).
5 VERIFY THAT REPAIRS HAVE BEEN COMPLETED
Yes Repeat the inspection from Step 1.

Go to the next step.
No Go to the next step.
6 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 [RETRACTABLE FASTBACK CONTROL MODULE] ).
No DTC troubleshooting completed.