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Home >> Mazda >> 2011 >> 3 Mazdaspeed, 2.3 3 >> Repair and Diagnosis >> Body & Frame >> Door Locks >> On-Board Diagnostic [Advanced Keyless Entry And Push Button Start System] >> DTC U0028:87 [Advanced Keyless Entry And Push Button Start System]
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DTC U0028:87 [Advanced Keyless Entry And Push Button Start System]

DESCRIPTION  Communication error with BCM 
DETECTION CONDITION 
  • Keyless control module receives the erratic signal from BCM.
  • Keyless control module cannot receive the signal from BCM.
POSSIBLE CAUSE 
  • BCM DTC is stored
  • BCM connector or terminals malfunction
  • Keyless control module connector or terminals malfunction
  • Short to ground in wiring harness between the following terminals:
    • BCM terminal 4K-Keyless control module terminal 3X
  • Short to power supply in wiring harness between the following terminals:
    • BCM terminal 4K-Keyless control module terminal 3X
  • Open circuit in wiring harness between the following terminals:
    • BCM terminal 4K-Keyless control module terminal 3X
  • BCM malfunction
  • Keyless control module malfunction
G07874869
DIAGNOSTIC PROCEDURE

Step Inspection Action
1 CONFIRM BCM DTC 
 Yes Go to the applicable DTC inspection.
(See DTC TABLE [BCM] ).
No Go to the next step.
2 INSPECT BCM CONNECTOR AND TERMINALS 
  • Switch the ignition to off.
  • Disconnect the negative battery cable.
  • Disconnect the BCM connector.
  • Inspect the connector and terminals (corrosion, damage, pin disconnection).
  • Is there any malfunction?
 Yes Repair or replace the connector or terminals, then go to Step 8.
No Go to the next step.
3 INSPECT KEYLESS CONTROL MODULE CONNECTOR AND TERMINALS 
  • Disconnect the keyless control module connector.
  • Inspect the connector and terminals (corrosion, damage, pin disconnection).
  • Is there any malfunction?
 Yes Repair or replace the connector or terminals, then go to Step 8.
No Go to the next step.
4 INSPECT COMMUNICATION CIRCUIT FOR SHORT TO GROUND 
  • BCM and keyless control module connectors are disconnected.
  • Inspect for continuity between the following terminal (wiring harness-side) and body ground:
    • BCM terminal 4K
  • Is there continuity?
 Yes Repair or replace the wiring harness for a possible short to ground, then go to Step 8.
No Go to the next step.
5 INSPECT COMMUNICATION CIRCUIT FOR SHORT TO POWER SUPPLY 
  • BCM and keyless control module connectors are disconnected.
  • Reconnect the negative battery cable.
  • Switch the ignition to ON.
  • Measure the voltage at the following terminal (wiring harness-side):
    • BCM terminal 4K
  • Is there any voltage?
 Yes Repair or replace the wiring harness for a possible short to power supply, then go to Step 8.
No Go to the next step.
6 INSPECT COMMUNICATION CIRCUIT FOR OPEN CIRCUIT 
  • BCM and keyless control module connectors are disconnected.
  • Switch the ignition to off.
  • Disconnect the negative battery cable.
  • Inspect for continuity between the following terminals (wiring harness-side):
    • BCM terminal 4K-Keyless control module terminal 3X
  • Is there continuity?
 Yes Go to the next step.
No Repair or replace the wiring harness for a possible open circuit, then go to Step 8.
7 VERIFY BCM MALFUNCTION 
 Yes Replace the BCM, then go to the next step.
(See BODY CONTROL MODULE (BCM) REMOVAL/INSTALLATION ).
No Go to the next step.
8 VERIFY TROUBLESHOOTING COMPLETED 
 Yes Replace the keyless control module, then go to the next step.
(See KEYLESS CONTROL MODULE REMOVAL/INSTALLATION ).
No Go to the next step.
9 VERIFY THAT NO OTHER DTCs ARE PRESENT 
  • Are any DTCs present?
 Yes Go to the applicable DTC inspection.
(See DTC TABLE [ADVANCED KEYLESS ENTRY AND PUSH BUTTON START SYSTEM] ).
No DTC troubleshooting completed.
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