Multiplex Control System Troubleshooting/DTC Troubleshooting: P0600 (39-1)

Special Tool Required:
MPCS Service Connector (  07WAZ-0010100)
 



1.Check the No. 9 (10 A) fuse in the under-hood fuse/relay box and the No. 10 (7.5 A) fuse in the under-dash fuse/relay box.

Are the fuses OK?


YES - Go to 2.


NO - Find and repair the cause of the blown fuse.n


2.Remove the driver's dashboard lower cover.

3.Switch the ceiling light to the middle position. Close all doors. Turn the ignition switch ON (II).
If the driver's seatbelt is unbuckled, the beeper will beep five times.

4.Check self-diagnosis function Mode 1 for a diagnostic trouble code (DTC) by connecting the special tool (A) to the multiplex control inspection connector (B). After about 5 seconds, the ignition switch light and ceiling light should come on for 2 seconds, go out, then blink once for 0.2 second. This means that you are in Mode 1 of the self-diagnosis function.

 

Did the blinking lights confirm that you are in model?


YES - Count the blinks, then go to 5.


NO - See if the SCS circuit is working properly. Go to 6.


5.If there is a DTC, it will blink, pause, then repeat the DTC as long as the ignition switch is ON (II).

Is there continuity?


YES - Count the blinks, then go to 8.


NO - Go to 9.


6.Check for continuity between the inspection connector T1 and body ground.

Is there continuity?


YES - Go to 9.


NO - Go to 7.


7.Check for continuity between the connector J of under-dash fuse/relay box No. 4 terminal and body ground.

Is there continuity?


YES - Faulty under-dash fuse/relay box. Replace and check for DTCs.


NO - Repair the open in the wire, and recheck for DTCs.n

8.About 1 second after you go into self-diagnosis mode 1, the ceiling light will indicate the DTC, and repeat it every 3 seconds. If there is more than one DTC, the system will indicate them in ascending order, beginning from the DTC with the lowest numerical value. Troubleshoot the DTCs as indicated below:

  • DTC 1, 2, and 3 (ECM/PCM P0600) simultaneously: Check for a short to body ground in the YEL wire between multiplex control unit terminal E10 and ECM/PCM terminal E24, and in the GRY/RED wire between multiplex control unit terminal K10 and gauge assembly terminal A1. If both wires are OK, substitute a known-good multiplex control unit, gauge assembly, and ECM/PCM one at a time, in that order, and recheck for the DTCs after each substitution.

  • DTC 2 and 5 simultaneously: Check for an open in the YEL wire between multiplex control unit terminal E10 and ECM/PCM terminal E24, If the wire is OK, substitute a known-good multiplex control unit, gauge assembly, and ECM/PCM one at a time, in that order, and recheck for the DTCs after each substitution.

  • DTC 1, and 6 simultaneously: Check for an open in the GRY/RED wire between multiplex control unit terminal K10 and gauge assembly terminal A1, If the wire is OK, substitute a known-good multiplex control unit, gauge assembly, and ECM/PCM one at a time, in that order, and recheck for the DTCs after each substitution.

  • DTC 1 only (no other DTCs present): Substitute a known-good multiplex control unit, and a gauge assembly one at a time, in that order, and recheck for the DTCs after each substitution.

  • DTC 2 only (no other DTCs present): Substitute a known-good multiplex control unit and a ECM/PCM one at a time, in that order, and recheck for the DTCs after each substitution.

  • DTC 3 only (no other DTCs present): Substitute a known-good multiplex control unit, and recheck for the DTC.

  • DTC 5 only (no other DTCs present): Substitute a known-good gauge assembly, and recheck for the DTC.
  • DTC 6 only (no other DTCs present): Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM, then recheck.If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM.n


DTC Cause 
The multiplex control unit cannot receive signals from the gauge assembly. 
The multiplex control unit cannot receive signals from the ECM/PCM. 
The multiplex control unit cannot receive signals from itself. 
The gauge assembly cannot receive signals from multiplex control unit and the ECM/PCM. 
The ECM/PCM cannot receive signals from multiplex control unit and the gauge assembly. 

9.From Mode 1, disconnect the special tool from the multiplex control inspection connector for about 5 to 10 seconds, then reconnect it. The ceiling light should come on for 2 seconds, then blink twice more at 0.2 second intervals. This means the system has gone from Mode 1 to Mode 2.

MODE 2: Ceiling Light Blinking Pattern 

NOTE: To cancel Mode 2, disconnect the SCS service connector from the multiplex control inspection connector for more than 10 seconds or turn the ignition switch OFF.

10.Look in the following table for the switches most closely related to the problem. While still in Mode 2, operate the switches and the control unit. If the circuit is OK, the spotlight and ceiling light should blink once. If the circuit is faulty, there will be no indication.

Does the ceiling light blink?


YES - Go to 12.


NO - Go to 11.

In each table below is a list of circuits that can be checked in Mode 2.

Taillight relay
Windshield washer switch (ON)
Windshield wiper motor (INT, Auto stop)
Driver's door switch (door opened)
Front passenger's door switch (door opened)
Left rear door switch (door opened)
Right rear door switch (door opened)
Ignition key switch (key in switch)
Tailgate switch (talgate opened)
Parking brake switch (ON)
Driver's door lock knob switch (LOCK/UNLOCK)
Passenger's door lock knob switch (UNLOCK)(KE model)
Left rear door lock knob switch (UNLOCK)(KE model)
Right rear door lock knob switch (UNLOCK)(KE model)
Driver's door key cylinder switch (LOCK/UNLOCK)
Driver's door lock switch (LOCK/UNLOCK)
Front passenger's door key cylinder switch (LOCK/UNLOCK)
Driver's seat belt switch (UNLATCH)
A/C switch (with fan switch ON)
Combination light switch
ECM/PCM communication line
Gauge assembly communication line
ABS communication
Front fog light switch(KE model)
Hatch glass (open) 

11.Check two or three other circuits listed above.

Does the spotlight and ceiling light blink for each circuit?


YES - The additional circuits are OK. Repair the short or open in the circuit that failed the test in step 10.n


NO - Multiplex failed circuits can mean that the control unit has failed, but without triggering a DTC. Test a few more circuits. If they also fail, test the multiplex control unit inputs. If all the input test are OK, substitute a known-good control unit, gauge assembly, or  ECM/ PCM, one at a time, then recheck. If the system works properly, the original control unit is faulty; replace it. If there is still a malfunction, substitute a known-good control unit for the next most likely faulty control unit, then recheck. If the system works properly, that control unit is faulty; replace it.n

12.Shift to the sleep mode:
Turn the ignition switch OFF, and remove the key.
If the control unit receivers no inputs from the inputs listed below, it will go into the sleep mode after about 20 seconds.

Multiplex Control Unit 
Taillight relay (combination switch OFF)
Driver's door switch (door closed)
Front passenger's door switch (door closed)
Left rear door switch (door closed)
Right rear door switch (door closed)
Tailgate switch (tailgate closed)
Driver's door key cylinder switch (LOCK/UNLOCK)
Hatch glass (glass closed) 

13.Comfirm the sleep mode:
Check for voltage on the YEL and WHT/GRN wires. There should be battery voltage in the sleep mode. Check the parasitic draw at the battery while shifting into the sleep mode. Amperage should change from about 70 through 80 mA to less than 10 mA.

14.Shift to the wake up mode:
When the ignition switch is turned ON (II), the multiplex control unit, gauge assembly, and ECM/PCM wake up at the same time without ‘‘talking'' to each other through the communication lines. When any switch in the multiplex system is turned on, it wakes up its related control unit which, in turn, wakes up the other units.

After confirming the sleep mode, look in the following table for the switch most closely related to the problem. Operate that switch and see if its control unit wakes up.

NOTE: If any control unit is faulty and will not wake up, several parts of the system will malfunction at the same time.
In the table below, the control unit is followed by a list of the switches and input signals that can wake it up.


Multiplex Control Unit No. 9 (10 A) under-hood fuse 
Communication lines (ECM/PCM, Gauge assembly) 
Taillight relay (combination switch ON)
Driver's door switch (door open)
Front passenger's door switch (door open)
Left rear door switch (door open)
Right rear door switch (door open)
Driver's door key cylinder switch (LOCK/UNLOCK)
Driver's door lock knob switch (LOCK/UNLOCK)
Driver's door lock switch (LOCK/UNLOCK)
Front passenger's door key cylinder switch (UNLOCK)
Ignition key switch (key in switch)
Tailgate switch (tailgate open) 

Is the wake-up function OK?


YES - Intermittent failure; the system is OK at this time.


NO - Test the multiplex control unit inputs.