HVAC DTC Troubleshooting: 4
DTC indicator 4: An Open in the Mode Control Motor Circuit
1.
Problem verification:

Problem verification
?1.
Turn the ignition switch to LOCK (0) and then back to ON (II).

?2.
Do the Self-Diagnostic Function with the HVAC control unit.

?3.
Check for DTCs.

Is DTC 4 indicated?

     
YES
     
     
     
Go to step 2.
     
NO
     
     
     
Intermittent failure. Check for loose wires or poor connections on the mode control motor circuit.?
2.
Open wire check (MDD-P/MODE-P line):

Open wire check (MDD-P/MODE-P line)
?1.
Turn the ignition switch to LOCK (0).

?2.
Disconnect the following connectors.

?3.
Check for continuity between test points 1 and 2.
Test condition
IG LOCK (0)
HVAC control unit 32P connector: disconnected
Mode control motor 7P connector: disconnected
Test circuit
MDD-P/MODE-P
Test point 1
HVAC control unit 32P connector No. 14 (GRN)
Test point 2
Mode control motor 7P connector No. 2 (PUR)


Is there continuity?

     
YES
     
     
     
The MDD-P/MODE-P wire is not open. Go to step 3.
     
NO
     
     
     
Repair an open in the wire between the HVAC control unit and the mode control motor.?
3.
Open wire check (SENSOR COM/SENS-COM line):

Open wire check (SENSOR COM/SENS-COM line)
?1.
Check for continuity between test points 1 and 2.
Test condition
IG LOCK (0)
HVAC control unit 32P connector: disconnected
Mode control motor 7P connector: disconnected
Test circuit
SENSOR COM/SENS-COM
Test point 1
Climate control unit 32P connector No. 20 (BLU)
Test point 2
Mode control motor 7P connector No. 3 (RED)


Is there continuity?

     
YES
     
     
     
The SENSOR COM/SENS-COM wire is not open. Go to step 4.
     
NO
     
     
     
Repair an open in the wire between the HVAC control unit and the mode control motor.?
4.
Shorted wire check (S 5V/S5V line to MDD-P/MODE-P line):

Shorted wire check (S 5V/S5V line to MDD-P/MODE-P line)
?1.
Check for continuity between test points 1 and 2.
Test condition
IG LOCK (0)
HVAC control unit 32P connector: disconnected
Mode control motor 7P connector: disconnected
Test circuit
S 5V, MDD-P
Test point 1
HVAC control unit 32P connector No. 14 (GRN)
Test point 2
HVAC control unit 32P connector No. 16 (BLK)


Is there continuity?

     
YES
     
     
     
Repair a short in the wires between the HVAC control unit and the mode control motor.?
     
NO
     
     
     
The S 5V/S5V wire to MDD-P/MODE-P wire are not shorted. Go to step 5.
5.
Mode control motor internal resistance check (S5V and SENS-COM):

Mode control motor internal resistance check (S5V and SENS-COM)
?1.
Measure the resistance between test points 1 and 2.
Test condition
IG LOCK (0)
HVAC control unit 32P connector: disconnected
Mode control motor 7P connector: disconnected
Test circuit
S5V, SENS-COM
Test point 1
Mode control motor No. 1
Test point 2
Mode control motor No. 3


Is the resistance 6 k?1.8 k??

     
YES
     
     
     
Go to step 6.
     
NO
     
     
     
6.
Mode control motor internal resistance check (S 5V and MDD-P):

Mode control motor internal resistance check (S 5V and MDD-P)
?1.
Reconnect the mode control motor 7P connector.

?2.
Connect the battery power and ground to terminals A and B, then reverse the connections.
Terminal A
HVAC control unit 32P connector No. 7 (GRN)
Terminal B
HVAC control unit 32P connector No. 8 (WHT)

NOTE: Incorrectly applying power and ground to the motor will damage it. Follow the instructions carefully. When the motor stops running, disconnect battery power immediately.


?3.
Measure the resistance between test points 1 and 2.
Test condition
IG LOCK (0)
HVAC control unit 32P connector: disconnected
Test circuit
S 5V, MDD-P
Test point 1
HVAC control unit 32P connector No. 14 (GRN)
Test point 2
HVAC control unit 32P connector No. 16 (BLK)

NOTE: Continuity between S 5V and MDD-P may disappear when the motor is turned to the stop. Usually the climate control unit does not turn the motor to the stop.


Does resistance change between about 0?6 k?1.8 k??

     
YES
     
     
     
     
NO