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Home >> Mazda >> 2023 >> MX-5 Miata Club >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> On-Board Diagnostic - Start Stop Unit >> DTC U201F-12: Keyless Receiver Circuit Malfunction [Start Stop Unit] >> Diagnostic Procedure

Diagnostic Procedure

DTC U201F:12 (START STOP UNIT) DIAGNOSTIC PROCEDURE

Step Inspection Action
1 INSPECT KEYLESS RECEIVER CONNECTOR CONDITION 
  • Switch the ignition off.
  • Disconnect the negative battery terminal. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION .)
  • Disconnect the keyless receiver 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 5.
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 5.
3 INSPECT KEYLESS RECEIVER CIRCUIT FOR SHORT TO POWER SUPPLY 
  • Reconnect the start stop unit connector.
  • Verify that the keyless receiver connector is disconnected.
  • Connect the negative battery terminal. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION .)
  • Switch the ignition ON (engine off or on).
  • Measure the voltage at the following terminals (wiring harness-side):
    • Keyless receiver terminal A
    • Start stop unit terminal 2Q
  • 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 start stop unit terminal 2Q and keyless receiver 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 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 INSPECT KEYLESS RECEIVER  Yes Go to the next step.
No Replace the keyless receiver, then go to the next step. (See KEYLESS RECEIVER REMOVAL/INSTALLATION .)
5 VERIFY THAT REPAIRS HAVE BEEN COMPLETED  Yes Repeat the inspection from Step 1.
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 [START STOP UNIT] .)
No DTC troubleshooting completed.