LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Mazda >> 2015 >> 3 SV, Automatic Trans >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Anti-Theft Systems >> On-Board Diagnostic - Advanced Keyless Entry System >> DTC B13C3: 29 Communication Error Between Start Stop Unit And LF Control Unit >> Diagnostic Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Diagnostic Procedure

DTC B13C3:29 DIAGNOSTIC PROCEDURE

Step Inspection Action
1 INSPECT LF CONTROL UNIT CONNECTOR CONDITION 
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 FOR SHORT TO GROUND IN WIRING HARNESS BETWEEN START STOP UNIT AND LF CONTROL UNIT 
  • Verify that the start stop unit and LF control unit connectors are disconnected.
  • Inspect for continuity between LF control unit terminal I (wiring harness-side) and body ground.
  • Is there continuity?
Yes Refer to the SYSTEM WIRING DIAGRAMS article and verify whether or not there is a common connector between start stop unit terminal 2F and LF control unit terminal I.
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 FOR OPEN CIRCUIT IN WIRING HARNESS BETWEEN START STOP UNIT AND LF CONTROL UNIT 
  • Verify that the start stop unit and LF control unit connectors are disconnected.
  • Inspect for continuity between start stop unit terminal 2F (wiring harness-side) and LF control unit terminal I (wiring harness-side).
  • Is there continuity?
Yes Go to the next step.
No Refer to the SYSTEM WIRING DIAGRAMS article and verify whether or not there is a common connector between start stop unit terminal 2F and LF control unit terminal I.
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 INSPECT LF CONTROL UNIT 
Yes Go to the next step.
No Replace the LF control unit, then go to the next step.
(See LF CONTROL UNIT REMOVAL/INSTALLATION .)
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 [ADVANCED KEYLESS ENTRY SYSTEM] .)
No DTC troubleshooting completed.