DTC U0028:87 [START STOP UNIT]


id0902p6023900

Description

Communication error with rear body control module (RBCM)

Detection condition
•  Start stop unit detects the communication error with rear body control module (RBCM) 10 times continuously.
Fail-safe function
•  Performs control with the driver's side door and trunk open.
Possible cause
•  Rear body control module (RBCM) connector or terminal malfunction
•  Start stop unit connector or terminal malfunction
•  Short to ground in wiring harness between start stop unit terminal 1Q and rear body control module (RBCM) terminal 3B
•  Open circuit in wiring harness between start stop unit terminal 1Q and rear body control module (RBCM) terminal 3B
•  Rear body control module (RBCM) malfunction
•  Start stop unit malfunction

Diagnostic Procedure

Step

Inspection

Action

1
INSPECT REAR BODY CONTROL MODULE (RBCM) CONNECTOR CONDITION
•  Switch the ignition off.
•  Disconnect the rear body control module (RBCM) 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 FOR SHORT TO GROUND IN WIRING HARNESS BETWEEN REAR BODY CONTROL MODULE AND START STOP UNIT
•  Verify that the rear body control module (RBCM) and start stop unit connectors are disconnected.
•  Inspect for continuity between rear body control module (RBCM) terminal 3B (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 rear body control module (RBCM) terminal 3B.
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 REAR BODY CONTROL MODULE AND START STOP UNIT
•  Verify that the rear body control module (RBCM) and start stop unit connectors are disconnected.
•  Inspect for continuity between start stop unit terminal 1Q (wiring harness-side) and rear body control module (RBCM) terminal 3B (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 rear body control module (RBCM) terminal 3B.
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
PERFORM DTC INSPECTION AND VERIFY REAR BODY CONTROL MODULE (RBCM) MALFUNCTION
•  Always reconnect all disconnected connectors.
•  Clear the DTC for the start stop unit using the M-MDS.
•  Retrieve the start stop unit DTCs using the M-MDS.
•  Is the same DTC displayed?
Yes
Replace the rear body control module (RBCM), then go to the next step.
No
Go to Step 7.
6
VERIFY THAT REPAIRS HAVE BEEN COMPLETED
•  Always reconnect all disconnected connectors.
•  Clear the DTC for the start stop unit using the M-MDS.
•  Retrieve the start stop unit DTCs using the M-MDS.
•  Is the same DTC displayed?
Yes
Repeat the inspection from Step 1.
•  If the malfunction recurs, replace the start stop unit.
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.
No
DTC troubleshooting completed.