DTC Troubleshooting: C1851-18 (63-01)
DTC C1851-18: Motor Circuit Low Current
NOTE: Before you troubleshoot, review the General Troubleshooting Information.

DTC Description
DTC
Freeze Frame
C1851-18 Motor Circuit Low Current
    

1.
Problem verification (with engine idling):

Problem verification (with engine idling)
?1.
Turn the vehicle to the ON mode.

?2.
Clear the DTC with the HDS.


?3.
Turn the vehicle to the OFF (LOCK) mode.

?4.
Start the engine.

?5.
Check for DTCs with the HDS.
DTC Description
DTC
Freeze Frame
C1851-18 Motor Circuit Low Current
    

Is DTC C1851-18 indicated?

     
YES
     
     
     
The failure is duplicated. Go to step 3.
     
NO
     
     
     
Go to step 2.
2.
Problem verification (with rear differential pump motor running):

Problem verification (with rear differential pump motor running)
?1.
Clear the DTC with the HDS.


?2.
Turn the vehicle to the OFF (LOCK) mode.

?3.
Turn the vehicle to the ON mode.

?4.
Select the ADJUSTMENT in the REAL TIME AWD with the HDS.

?5.
With the engine running, do the AIR BLEEDING in the ADJUSTMENT with the HDS.

  

?6.
Check for DTCs with the HDS.
DTC Description
DTC
Freeze Frame
C1851-18 Motor Circuit Low Current
    

Is DTC C1851-18 indicated?

     
YES
     
     
     
The failure is duplicated. Go to step 3.
     
NO
     
     
     
Intermittent failure, the system is OK at this time. If the freeze data/on-board snapshot of this DTC is recorded, try to reproduce the failure under the same conditions with the freeze data/on-board snapshot.?
3.
Open wire check (GND line):

Open wire check (GND line)
?1.
Turn the vehicle to the OFF (LOCK) mode.

?2.
Disconnect the following connector.
AWD control unit 24P connector

?3.
Check for continuity between test points 1 and 2.
Test condition
Vehicle OFF (LOCK) mode
 
AWD control unit 24P connector: disconnected
Test point 1
AWD control unit 24P connector No. 4
Test point 2
Body ground

Is there continuity?

     
YES
     
     
     
The GND wire is OK. Go to step 4.
     
NO
     
     
     
Check for poor connections or loose terminals between the AWD control unit and ground (G503). If the connections are OK, repair an open in the GND wire between the AWD control unit and ground (G503).?
4.
Determine possible failure area (short in MH, ML lines, open in MH, ML lines):

Determine possible failure area (short in MH, ML lines, open in MH, ML lines)
?1.
Check for continuity between test points 1 and 2.
Test condition
Vehicle OFF (LOCK) mode
 
AWD control unit 24P connector: disconnected
Test point 1
AWD control unit 24P connector No. 1
Test point 2
Body ground

Is there continuity?

     
YES
     
     
     
Go to step 7.
     
NO
     
     
     
Go to step 5.
5.
Determine possible failure area (MH, ML lines, AWD control unit):

Determine possible failure area (MH, ML lines, AWD control unit)
?1.
Measure the resistance between test points 1 and 2.
Test condition
Vehicle OFF (LOCK) mode, At normal air temperature
 
AWD control unit 24P connector: disconnected
Test point 1
AWD control unit 24P connector No. 1
Test point 2
AWD control unit 24P connector No. 3

Is there about 10 ? or less?

     
YES
     
     
     
Check for any authorized service information related to the DTCs or symptoms you are troubleshooting or substitute a known-good AWD control unit, and recheck. If the symptom/indication goes away with a known-good AWD control unit, replace the original AWD control unit.?
     
NO
     
     
     
Go to step 6.
6.
Rear differential pump motor internal open check:

Rear differential pump motor internal open check
?1.
Disconnect the following connector.
Rear differential pump motor 2P connector

?2.
On the rear differential pump motor side, measure the resistance between test points 1 and 2.
Test condition
Vehicle OFF (LOCK) mode
 
AWD control unit 24P connector: disconnected
 
Rear differential pump motor 2P connector: disconnected
Test point 1
Rear differential pump motor 2P connector (male terminals) No. 1:
Test point 2
Rear differential pump motor 2P connector (male terminals) No. 2:


Is there about 10 ? or less?

     
YES
     
     
     
Repair an open in the MH and/or ML wires between the rear differential pump motor and the AWD control unit.?
     
NO
     
     
     
7.
Rear differential pump motor internal shorted check:

Rear differential pump motor internal shorted check
?1.
Disconnect the following connector.
Rear differential pump motor 2P connector

?2.
Check for continuity between the following test points 1 and 2 individually (see table).
Test condition
Vehicle OFF (LOCK) mode
 
AWD control unit 24P connector: disconnected
 
Rear differential pump motor 2P connector: disconnected

Connector
Test point 1
Test point 2
Rear differential pump motor 2P connector (male terminals)
No. 1:
Rear differential pump motor body
No. 2:


Are there continuity?

     
YES
     
     
     
     
NO
     
     
     
Repair a short to ground in the MH and/or ML wires between the rear differential pump motor and the AWD control unit.?