brake sensor INFINITI QX56 2004 Factory Workshop Manual

DTC P1772 LOW COAST BRAKE SOLENOID VALVE
AT-169
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Revision: August 20072004 QX56
DTC P1772 LOW COAST BRAKE SOLENOID VALVEPFP:31940
DescriptionUCS002H C
Low coast brake solenoid valve is turned “ON” or “OFF” by the TCM in response to signals sent from the PNP
switch, vehicle speed sensor and accelerator pedal position sensor (throttle position sensor). Gears will then
be shifted to the optimum position.
CONSULT-II Reference ValueUCS002H D
On Board Diagnosis LogicUCS002HE

This is an OBD-II self-diagnostic item.

Diagnostic trouble code “LC/B SOLENOID/CIRC” with CONSULT-II or P1772 without CONSULT-II is
detected when TCM detects an improper voltage drop when it tries to operate the solenoid valve.
Possible CauseUCS002HF

Harness or connectors
(The solenoid circuit is open or shorted.)

Low coast brake solenoid valve
DTC Confirmation ProcedureUCS002HG
NOTE:
If “DTC Confirmation Procedure” has been previously performed, always turn ignition switch “OFF”
and wait at least 10 seconds before performing the next test.
After the repair, perform the following procedure to confirm the malfunction is eliminated.
WITH CONSULT-II
1. Turn ignition switch “ON”. (Do not start engine.)
2. Select “DATA MONITOR” mode for “ENGINE” with CONSULT-II.
3. Start engine.
4. Drive vehicle and maintain the following conditions for at least 5
consecutive seconds.
Selector lever: “1” or “2”
Gear position: “1st” or “2nd” gear (LC/B ON/OFF)
5. If DTC is detected, go to AT - 1 7 0 , "
Diagnostic Procedure" .
WITH GST
Follow the procedure “With CONSULT-II”.
Item name Condition Display value (ON-OFF display)
ON OFF SOLLow coast brake engaged. Refer to AT-2 1
.ON
Low coast brake disengaged. Refer to AT- 2 1
.OFF
BCIA0030E

AT-170
DTC P1772 LOW COAST BRAKE SOLENOID VALVE
Revision: August 20072004 QX56
Diagnostic ProcedureUCS002HH
1. CHECK INPUT SIGNAL
With CONSULT-II
1. Turn ignition switch “ON”. (Do not start engine.)
2. Select “SELECTION FROM MENU” in “DATA MONITOR” mode
for “A/T” with CONSULT-II.
3. Start the engine.
4. Read out the value of “ON OFF SOL” while driving.
OK or NG
OK >> GO TO 6.
NG >> GO TO 2.
2. CHECK TCM
Perform TCM input/output signals inspection. Refer to AT- 9 0 , "
TCM Input/Output Signal Reference Values" .
OK or NG
OK >> GO TO 3.
NG >> GO TO 5.
3. CHECK DTC
Perform “DTC Confirmation Procedure”.

Refer to AT-169, "DTC Confirmation Procedure" .
OK or NG
OK >>INSPECTION END
NG >> GO TO 4.
4. DETECT MALFUNCTIONING ITEM
Check the following items:

The A/T assembly harness connector terminals for damage or loose connection with harness connector.
OK or NG
OK >> Replace the control valve with TCM. Refer to AT-241, "Control Valve With TCM and A/T Fluid
Temperature Sensor 2" .
NG >> Repair or replace damaged parts.
5. DETECT MALFUNCTIONING ITEM
Check the following items:

Power supply and ground circuit for TCM.

The A/T assembly harness connector terminals for damage or loose connection with harness connector.
OK or NG
OK >> GO TO 6.
NG >> Repair or replace damaged parts.
Item name Condition Display value (ON-OFF display)
ON OFF SOLLow coast brake engaged.
Refer to AT- 2 1
.ON
Low coast brake disengaged.
Refer to AT- 2 1
.OFFSCIA4794E

AT-172
DTC P1774 LOW COAST BRAKE SOLENOID VALVE FUNCTION
Revision: August 20072004 QX56
DTC P1774 LOW COAST BRAKE SOLENOID VALVE FUNCTIONPFP:31940
DescriptionUCS002HI

Low coast brake solenoid valve is turned “ON” or “OFF” by the TCM in response to signals sent from the
PNP switch, vehicle speed sensor and accelerator pedal position sensor (throttle position sensor). Gears
will then be shifted to the optimum position.

This is not only caused by electrical malfunction (circuits open or shorted) but also by mechanical mal-
function such as control valve sticking, improper solenoid valve operation.
CONSULT-II Reference ValueUCS002HJ
On Board Diagnosis LogicUCS002HK

This is an OBD-II self-diagnostic item.

Diagnostic trouble code “LC/B SOLENOID FNCT” with CONSULT-II or P1774 without CONSULT-II is
detected under the following conditions.
–When TCM detects that actual gear ratio is irregular, and relation between gear position and condition of
ATF pressure switch 2 is irregular during depressing accelerator pedal. (Other than during shift change)
–When TCM detects that relation between gear position and condition of ATF pressure switch 2 is irregular
during releasing accelerator pedal. (Other than during shift change)
Possible CauseUCS002HL

Harness or connectors
(The solenoid and switch circuits are open or shorted.)

Low coast brake solenoid valve

ATF pressure switch 2
DTC Confirmation ProcedureUCS002HM
CAUTION:
Always drive vehicle at a safe speed.
NOTE:
If “DTC Confirmation Procedure” has been previously performed, always turn ignition switch “OFF”
and wait at least 10 seconds before performing the next test.
After the repair, perform the following procedure to confirm the malfunction is eliminated.
WITH CONSULT-II
1. Start engine.
2. Accelerate vehicle to maintain the following conditions.
Selector lever: “1” or “2” position
Gear position: “1st” or “2nd” gear (LC/B ON/OFF)
3. Perform step “2” again.
4. Turn ignition switch “OFF”, then perform step “1” to “3” again.
5. Check “SELF-DIAG RESULTS” mode for “A/T” with CONSULT-
II. If DTC (P1774) is detected, refer to AT-173, "
Diagnostic Pro-
cedure" .
If DTC (P1772) is detected, go to AT-170, "
Diagnostic Proce-
dure" .
WITH GST
Follow the procedure “With CONSULT-II”.
Item name Condition Display value (ON-OFF display)
ON OFF SOLLow coast brake engaged. Refer to AT- 2 1
. ON
Low coast brake disengaged. Refer to AT- 2 1
. OFF
ATF PRES SW 2Low coast brake engaged. Refer to AT- 2 1
. ON
Low coast brake disengaged. Refer to AT- 2 1
. OFF
BCIA0030E

DTC P1774 LOW COAST BRAKE SOLENOID VALVE FUNCTION
AT-173
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Diagnostic ProcedureUCS002H N
1. CHECK INPUT SIGNALS
With CONSULT-II
1. Turn ignition switch “ON”. (Do not start engine.)
2. Select “SELECTION FORM MENU” in “DATA MONITOR” mode
for “A/T” with CONSULT-II.
3. Start the engine.
4. Drive vehicle in the manual mode (“M1-1st” or “M2-2nd” gear),
and confirm the ON/OFF actuation of the “ATF PRES SW 2” and
“ON OFF SOL”.
OK or NG
OK >> GO TO 6.
NG >> GO TO 2.
2. CHECK TCM
Perform TCM input/output signals inspection. Refer to AT-90, "
TCM Input/Output Signal Reference Values" .
OK or NG
OK >> GO TO 3.
NG >> GO TO 5.
3. CHECK DTC
Perform “DTC Confirmation Procedure”.

Refer to AT- 1 7 2 , "DTC Confirmation Procedure" .
OK or NG
OK >>INSPECTION END
NG >> GO TO 4.
4. DETECT MALFUNCTIONING ITEM
Check the following items:

The A/T assembly harness connector terminals for damage or loose connection with harness connector.
OK or NG
OK >> Replace the control valve with TCM. Refer to AT - 2 4 1 , "Control Valve With TCM and A/T Fluid
Temperature Sensor 2" .
NG >> Repair or replace damaged parts.
Item name Condition Display value
(ON-OFF dis-
play)
ON OFF SOLLow coast brake engaged. Refer to
AT- 2 1
.ON
Low coast brake disengaged. Refer
to AT-2 1
.OFF
ATF PRES
SW 2Low coast brake engaged. Refer to
AT- 2 1
.ON
Low coast brake disengaged. Refer
to AT-2 1
.OFF
SCIA4794E

AT-176
DTC P1841 ATF PRESSURE SWITCH 1
Revision: August 20072004 QX56
Diagnostic ProcedureUCS002HT
1. CHECK INPUT SIGNAL
With CONSULT-II
1. Start engine.
2. Select “ECU INPUT SIGNALS” or “MAIN SIGNALS” in “DATA
MONITOR” mode for “A/T” with CONSULT-II.
3. Drive vehicle in the “D” position (3rd

4th gear), and confirm
the ON/OFF actuation of the “ATF PRES SW 1”.
OK or NG
OK >> GO TO 6.
NG >> GO TO 2.
2. CHECK TCM
Perform TCM input/output signals inspection. Refer to AT- 9 0 , "
TCM Input/Output Signal Reference Values" .
OK or NG
OK >> GO TO 3.
NG >> GO TO 5.
3. CHECK DTC
Perform “DTC Confirmation Procedure”.

Refer to AT-175, "DTC Confirmation Procedure" .
OK or NG
OK >>INSPECTION END
NG >> GO TO 4.
4. DETECT MALFUNCTIONING ITEM
Check the following items:

The A/T assembly harness connector terminals for damage or loose connection with harness connector.
OK or NG
OK >> Replace the control valve with TCM. Refer to AT-241, "Control Valve With TCM and A/T Fluid
Temperature Sensor 2" .
NG >> Repair or replace damaged parts.
5. DETECT MALFUNCTIONING ITEM
Check the following items:

Power supply and ground circuit for TCM.

The A/T assembly harness connector pin terminals for damage or loose connection with harness connec-
tor.
OK or NG
OK >> GO TO 6.
NG >> Repair or replace damaged parts.
Item name Condition Display value (ON-OFF
display)
ATF PRES
SW 1Front brake engaged. Refer to AT-2 1
.ON
Front brake disengaged. Refer to AT-2 1
.OFFPCIA0067E

TROUBLE DIAGNOSIS FOR SYMPTOMS
AT-195
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Revision: August 20072004 QX56
5. CHECK SYMPTOM
Check again. Refer to AT- 6 2 , "
Check at Idle" .
OK or NG
OK >>INSPECTION END
NG >> GO TO 6.
6. PERFORM TCM INSPECTION
1. Perform TCM input/output signals inspection. Refer to AT-90, "
TCM Input/Output Signal Reference Val-
ues" .
2. If NG, recheck A/T assembly harness connector terminals for damage or loose connection with harness
connector.
OK or NG
OK >>INSPECTION END
NG >> Repair or replace damaged parts.
Large Shock (“N” to “D” Position)UCS002IM
SYMPTOM:
A noticeable shock occurs when the selector lever is shifted from the “N” to “D” position.
DIAGNOSTIC PROCEDURE
1. CHECK SELF-DIAGNOSTIC RESULTS
Perform self-diagnosis. Refer to AT- 9 3 , "
SELF-DIAGNOSTIC RESULT MODE" .
Do the self-diagnostic results indicate A/T fluid temperature sensor, engine speed signal, accelerator pedal
position sensor, ATF pressure switch 1, front brake solenoid valve, CAN communication line?
YES >> Check the malfunctioning system. Refer to AT-131, "DTC P1710 A/T FLUID TEMPERATURE
SENSOR CIRCUIT" , AT-115, "DTC P0725 ENGINE SPEED SIGNAL" ., AT- 1 2 9 , "DTC P1705
THROTTLE POSITION SENSOR" , AT-175, "DTC P1841 ATF PRESSURE SWITCH 1" , AT-
151, "DTC P1757 FRONT BRAKE SOLENOID VALVE" , AT- 1 0 3 , "DTC U1000 CAN COMMUNI-
CATION LINE" .
NO >> GO TO 2.
2. ENGINE IDLE SPEED
Check the engine idle speed. Refer to EC-32, "
Idle Speed and Ignition Timing Check" .
OK or NG
OK >> GO TO 3.
NG >> Repair.
3. CHECK CONTROL CABLE
Check the control cable.

Refer to AT- 2 3 4 , "Checking of A/T Position" .
OK or NG
OK >> GO TO 4.
NG >> Adjust control cable. Refer to AT-234, "
Adjustment of A/
T Position" .
LCIA0324E

AT-210
TROUBLE DIAGNOSIS FOR SYMPTOMS
Revision: August 20072004 QX56
8. DETECT MALFUNCTIONING ITEM

Check the malfunction items. If any items are damaged, repair or replace damaged parts. Refer to AT-68,
"Symptom Chart" (Symptom No.11).
OK or NG
OK >> GO TO 9.
NG >> Repair or replace damaged parts.
9. CHECK SYMPTOM
Check again. Refer to AT-63, "
Cruise Test - Part 1" , AT-65, "Cruise Test - Part 2" .
OK or NG
OK >>INSPECTION END
NG >> GO TO 10.
10. PERFORM TCM INSPECTION
1. Perform TCM input/output signals inspection. Refer to AT- 9 0 , "
TCM Input/Output Signal Reference Val-
ues" .
2. If NG, recheck A/T assembly harness connector terminals for damage or loose connection with harness
connector.
OK or NG
OK >>INSPECTION END
NG >> Repair or replace damaged parts.
11 . DETECT MALFUNCTIONING ITEM

Check the malfunction items. If any items are damaged, repair or replace damaged parts. Refer to AT-68,
"Symptom Chart" (Symptom No.11).
OK or NG
OK >> GO TO 9.
NG >> Repair or replace damaged parts.
A/T Does Not Shift: D3 → D4UCS002IS
SYMPTOM:

The vehicle does not shift-up from the D3 to D4 gear at the specified speed.

The vehicle does not shift-up from the D3 to D4 gear unless A/T is warmed up.
DIAGNOSTIC PROCEDURE
1. CONFIRM THE SYMPTOM
Check if vehicle creeps forward in “D” position and vehicle can be started from D
1.
OK or NG
OK >> GO TO 2.
NG >> Refer to AT-201, "
Vehicle Does Not Creep Forward In “D” Position" , AT - 2 0 3 , "Vehicle Cannot Be
Started From D1" .
2. CHECK SELF-DIAGNOSTIC RESULTS
Perform self-diagnosis. Refer to AT- 9 3 , "
SELF-DIAGNOSTIC RESULT MODE" .
Do the self-diagnostic results indicate ATF pressure switch 1, ATF pressure switch 3, front brake solenoid
valve, input clutch solenoid valve, accelerator pedal position sensor, vehicle speed sensor A/T (revolution sen-
sor) and vehicle speed sensor MTR?
YES >> Check the malfunctioning system. Refer to AT-175, "DTC P1841 ATF PRESSURE SWITCH 1" ,
AT-178, "
DTC P1843 ATF PRESSURE SWITCH 3" , AT-145, "DTC P1752 INPUT CLUTCH
SOLENOID VALVE" , AT-151, "DTC P1757 FRONT BRAKE SOLENOID VALVE" , AT-129, "DTC

TROUBLE DIAGNOSIS FOR SYMPTOMS
AT-213
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Revision: August 20072004 QX56
A/T Does Not Shift: D4 → D5UCS002IT
SYMPTOM:

The vehicle does not shift-up from the D4 to D5 gear at the specified speed.

The vehicle does not shift-up from the D4 to D5 gear unless A/T is warmed up.
DIAGNOSTIC PROCEDURE
1. CONFIRM THE SYMPTOM
Check if vehicle creeps forward in “D” position and vehicle can be started from D
1.
OK or NG
OK >> GO TO 2.
NG >> Refer to AT- 2 0 1 , "
Vehicle Does Not Creep Forward In “D” Position" , AT-203, "Vehicle Cannot Be
Started From D1" .
2. CHECK SELF-DIAGNOSTIC RESULTS
Perform self-diagnosis. Refer to AT- 9 3 , "
SELF-DIAGNOSTIC RESULT MODE" .
Do the self-diagnostic results indicate ATF pressure switch 1, ATF pressure switch 5, front brake solenoid
valve, direct clutch solenoid valve, accelerator pedal position sensor, turbine revolution sensor, vehicle speed
sensor A/T (revolution sensor) and vehicle speed sensor MTR?
YES >> Check the malfunctioning system. Refer to AT- 1 7 5 , "DTC P1841 ATF PRESSURE SWITCH 1" ,
AT-181, "
DTC P1845 ATF PRESSURE SWITCH 5" , AT-151, "DTC P1757 FRONT BRAKE
SOLENOID VALVE" , AT-157, "DTC P1762 DIRECT CLUTCH SOLENOID VALVE" , AT-129,
"DTC P1705 THROTTLE POSITION SENSOR" , AT-134, "DTC P1716 TURBINE REVOLUTION
SENSOR" , AT - 11 2 , "DTC P0720 VEHICLE SPEED SENSOR A/T (REVOLUTION SENSOR)" ,
AT-136, "
DTC P1721 VEHICLE SPEED SENSOR MTR" .
NO >> GO TO 3.
3. CHECK A/T FLUID LEVEL
Check A/T fluid level. Refer to AT- 1 3 , "
Checking A/T Fluid" .
OK or NG
OK >> GO TO 4.
NG >> Refill ATF.
4. CHECK LINE PRESSURE
Check line pressure at the engine stall point. Refer to AT-59, "
LINE
PRESSURE TEST" .
OK or NG
OK >> GO TO 7.
NG - 1 >> Line pressure high. GO TO 5.
NG - 2 >> Line pressure low. GO TO 6.
SAT6 3 8A
SAT4 9 4G

AT-220
TROUBLE DIAGNOSIS FOR SYMPTOMS
Revision: August 20072004 QX56
Engine Speed Does Not Return to IdleUCS002IX
SYMPTOM:
When a shift-down is performed, the engine speed does not smoothly return to the idling speed.
DIAGNOSTIC PROCEDURE
1. CHECK A/T FLUID LEVEL
Check A/T fluid level. Refer to AT-13, "
Checking A/T Fluid" .
OK or NG
OK >> GO TO 2.
NG >> Refill ATF.
2. CHECK SELF-DIAGNOSTIC RESULTS
Perform self-diagnosis. Refer to AT- 9 3 , "
SELF-DIAGNOSTIC RESULT MODE" .
Do the self-diagnostic results indicate front brake solenoid valve, direct clutch solenoid valve, ATF pressure
switch 1, ATF pressure switch 5, accelerator pedal position sensor, vehicle speed sensor A/T (revolution sen-
sor) and vehicle speed sensor MTR?
YES >> Check the malfunctioning system. Refer to AT-151, "DTC P1757 FRONT BRAKE SOLENOID
VA LV E" , AT-157, "DTC P1762 DIRECT CLUTCH SOLENOID VALVE" , AT- 1 7 5 , "DTC P1841
ATF PRESSURE SWITCH 1" , AT-181, "DTC P1845 ATF PRESSURE SWITCH 5" , AT-129,
"DTC P1705 THROTTLE POSITION SENSOR" , AT- 11 2 , "DTC P0720 VEHICLE SPEED SEN-
SOR A/T (REVOLUTION SENSOR)" , AT-136, "DTC P1721 VEHICLE SPEED SENSOR MTR" .
NO >> GO TO 3.
3. CHECK A/T FLUID CONDITION
1. Remove oil pan. Refer to AT-241, "
Control Valve With TCM and A/T Fluid Temperature Sensor 2" .
2. Check A/T fluid condition. Refer to AT- 5 8 , "
Fluid Condition
Check" .
OK or NG
OK >> GO TO 4.
NG >> GO TO 7.
4. DETECT MALFUNCTIONING ITEM

Check the malfunction items. If any items are damaged, repair or replace damaged parts. Refer to AT-68,
"Symptom Chart" (Symptom No.65).
OK or NG
OK >> GO TO 5.
NG >> Repair or replace damaged parts.
SAT6 3 8A
SCIA5199E

AT-284
DISASSEMBLY
Revision: August 20072004 QX56
43. Remove parking gear from output shaft.
44. Remove seal rings from output shaft.
45. Remove needle bearing from transmission case.
46. Remove revolution sensor from transmission case.
CAUTION:

Do not subject it to impact by dropping or hitting it.

Be careful not to damage harness with the edge of case.

Do not allow metal filings, etc., to get on the sensor's
front edge magnetic area.

Do not place in an area affected by magnetism.
47. Remove reverse brake snap ring (fixing plate) using 2 flat-
bladed screwdrivers.
NOTE:
Press out snap ring from the transmission case oil pan side gap
using a flat-bladed screwdriver, and remove it using another
screwdriver.
48. Remove reverse brake retaining plate from transmission case.
SCIA5247E
SCIA5209E
SCIA5213E
SCIA2320E
SCIA5032E