LEMON Manuals: Even more car manuals for everyone
Home >> Mazda >> 2023 >> MX-5 Miata Club >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> On-Board Diagnostic - Start Stop Unit >> DTC U0028-87: Communication Error With BCM [Start Stop Unit] >> Diagnostic Procedure

Diagnostic Procedure

DTC U0028:87 (START STOP UNIT) DIAGNOSTIC PROCEDURE

Step Inspection Action
1 INSPECT BCM CONNECTOR CONDITION 
  • Switch the ignition off.
  • Disconnect the negative battery terminal. (See NEGATIVE BATTERY TERMINAL 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.
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.
scientia non olet · About LEMON Manuals