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Home >> Mazda >> 2012 >> 6 i Touring >> Repair and Diagnosis >> External Pages >> Different car >> Section 548 (On-Board Diagnostic [Multiplex Communication System)) >> M-MDS And Vehicle Not Communicating [Multiplex Communication System] >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2009 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION:
  • When disconnecting the connector, verify that there is no looseness, damage, deformation, corrosion, or poor connection of the connector terminals.
Step Inspection Action
1 VERIFICATION BEFORE SERVICING 
  • Is there communication between the M-MDS and vehicle?
 Yes Go to the next step.
No Go back to FOREWORD [MULTIPLEX COMMUNICATION SYSTEM (See FOREWORD [MULTIPLEX COMMUNICATION SYSTEM] .)
2 VERIFY THAT M-MDS AND DLC-2 ARE CONNECTED 
  • Verify the connection condition between the M-MDS and DLC-2.
  • Are the connector terminals normal without damage, deformation, corrosion, or disconnection?
 Yes Go to the next step
No Correct the connection condition, then go to Step 12.
3 VERIFY PCM POWER SUPPLY CONDITION  Yes Go to the next step.
No Repair or replace the fuse or wiring harness, then go to Step 12.
4 VERIFY PCM BODY GROUND CONDITION 
  • Inspect the PCM body ground wiring harness and ground point
  • Are the ground and ground point normal?
 Yes Go to the next step
No Repair or replace the wiring harness, then go to Step 12.
5 INSPECT PCM CONNECTOR TERMINAL 
  • Disconnect the negative battery cable
  • Disconnect the PCM connector.
  • Are the PCM connector terminal normal without damage, deformation, corrosion, or disconnection?
 Yes Go to the next step.
No Repair the connector terminal if necessary, then go to Step 12
6 INSPECT PCM 
  • Disconnect the PCM connector
  • Measure the resistance between the following PCM connector terminals
    • Between terminal 1AM and terminal 1AI (part side) (L5)
    • Between terminal 1AH and terminal 1AL (part side) (MZI-3 7)
  • Is the resistance 118-130 ohm?
 Yes Go to the next step.
No Replace the PCM, then go to the next step. (See PCM REMOVAL/INSTALLATION [MZI-3.7] .) (See PCM REMOVAL/INSTALLATION [L5] .)
7 VERIFY THAT THERE IS NO OPEN CIRCUIT IN CAN COMMUNICATION WIRING HARNESS 
CAUTION:
  • When inspecting the DLC-2, touch it with a paper clip or similar thin pin without directly inserting a tester into the terminals.
  • Verify the continuity between the following terminals.
    • Between DLC-2 terminal F and PCM terminal 1AM (L5)
    • Between DLC-2 terminal E and PCM terminal 1AI (L5)
    • Between DLC-2 terminal F and PCM terminal 1AH (MZI-3.7)
    • Between DLC-2 terminal E and PCM terminal 1AL (MZI-3 7)
  • Is there continuity?
 Yes Go to the next step.
No There is an open circuit in the CAN communication wiring harness. Repair or replace it, then go to Step 12.
8 VERIFY THAT THERE IS NO SHORT CIRCUIT IN CAN COMMUNICATION WIRING HARNESS 
CAUTION:
  • When inspecting the DLC-2, touch it with a paper clip or similar thin pin without directly inserting a tester into the terminals.
  • Measure the resistance between the terminals.
    • Between DLC-2 terminal F and DLC-2 terminal E
  • Is the resistance 60 ohm or less?
 Yes There is an open circuit in the CAN communication wiring harness Repair or replace it, then go to Step 12.
No Go to the next step
9 VERIFY NO SHORT CIRCUIT TO GROUND IN CAN COMMUNICATION WIRING HARNESS 
CAUTION:
  • When inspecting the DLC-2, touch it with a paper clip or similar thin pin without directly inserting a tester into the terminals.
  • Verify the continuity between the following terminals
    • Between DLC-2 terminal F and ground
    • Between DLC-2 terminal E and ground
    • Between PCM terminal 1AM and ground (L5)
    • Between PCM terminal 1AI and ground (L5)
    • Between PCM terminal 1AH and ground (MZI-3 7)
    • Between PCM terminal 1AL and ground (MZI-3 7)
  • Is there continuity?
 Yes There is a short circuit to ground in the CAN communication wiring harness. Repair or replace it, then go to Step 12.
No Go to the next step
10 VERIFY NO SHORT CIRCUIT TO POWER SUPPLY SYSTEM IN CAN COMMUNICATION WIRING HARNESS 
CAUTION:
  • When inspecting the DLC-2, touch it with a paper clip or similar thin pin without directly inserting a tester into the terminals.
  • Verify the continuity between the following terminals
    • Between DLC-2 terminal F and DLC-2 terminal O
    • Between DLC-2 terminal A and DLC-2 terminal O
    • Between PCM terminal 1AM and PCM terminal 1C (L5)
    • Between PCM terminal 1AI and PCM terminal 1C (L5)
    • Between PCM terminal 1AH and PCM terminal 1V (MZI-3.7)
    • Between PCM terminal 1AL and PCM terminal 1V (MZI-3 7)
  • Is there continuity?
 Yes There is a short circuit to the power supply system in the CAN communication wiring harness Repair or replace it, then go to Step 12
No Go to the next step.
11 INSPECT CAN-RELATED MODULES OTHER THAN PCM 
  • Remove only one of the CAN-related modules other than those related to the PCM
  • Connect the negative battery cable
  • Connect the M-MDS to the DLC-2
  • Does the M-MDS recognize the vehicle?
 Yes Replace the removed module.
No Inspect all of the CAN-related modules other than those related to the PCM using the same procedure. After inspecting all of the modules, go to the next step.
12 PERFORM VEHICLE IDENTIFICATION 
  • Connect the M-MDS to the DLC-2.
  • Does the M-MDS recognize the vehicle?
 Yes DTC troubleshooting completed.
No Replace the PCM. (See PCM REMOVAL/INSTALLATION [MZI-3.7] .) (See PCM REMOVAL/INSTALLATION [L5] .)
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