2004 INFINITI QX56 check engine

DTC P1774 LOW COAST BRAKE SOLENOID VALVE FUNCTION
AT-173
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Revision: August 20072004 QX56
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

DTC P1841 ATF PRESSURE SWITCH 1
AT-175
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Revision: August 20072004 QX56
DTC P1841 ATF PRESSURE SWITCH 1PFP:25240
DescriptionUCS002HO
Fail-safe function to detect front brake clutch solenoid valve condition.
CONSULT-II Reference ValueUCS002HP
On Board Diagnosis LogicUCS002HQ

This is not an OBD-II self-diagnostic item.

Diagnostic trouble code “ATF PRES SW 1/CIRC” with CONSULT-II is detected when TCM detects that
actual gear ratio is normal, and relation between gear position and condition of ATF pressure switch 1 is
irregular during depressing accelerator pedal. (Other than during shift change)
Possible CauseUCS002H R

ATF pressure switch 1

Harness or connectors
(The switch circuit is open or shorted.)
DTC Confirmation ProcedureUCS002HS
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.
ACCELE POS: 1.5/8 - 2.0/8
Selector lever: “D” position
Gear position: 3rd

4th Gear (FR/B ON/OFF)
Driving location: Driving the vehicle uphill (increased
engine load) will help maintain the driving conditions
required for this test.
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 (P1841) is detected, go to AT-176, "
Diagnostic Procedure" .
If DTC (P1757) is detected, go to AT-152, "
Diagnostic Procedure" .
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
. OFF
BCIA0030E

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

AT-178
DTC P1843 ATF PRESSURE SWITCH 3
Revision: August 20072004 QX56
DTC P1843 ATF PRESSURE SWITCH 3PFP:25240
DescriptionUCS002HU
Fail-safe function to detect input clutch solenoid valve condition.
CONSULT-II Reference ValueUCS002HV
On Board Diagnosis LogicUCS002HW

This is not an OBD-II self-diagnostic item.

Diagnostic trouble code “ATF PRES SW 3/CIRC” with CONSULT-II is detected when TCM detects that
actual gear ratio is normal, and relation between gear position and condition of ATF pressure switch 3 is
irregular during depressing accelerator pedal. (Other than during shift change)
Possible CauseUCS002HX

ATF pressure switch 3

Harness or connectors
(The switch circuit is open or shorted.)
DTC Confirmation ProcedureUCS002HY
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.
ACCELE POS: 1.5/8 - 2.0/8
Selector lever: “D” position
Gear position: 3rd

4th Gear (I/C ON/OFF)
Driving location: Driving the vehicle uphill (increased
engine load) will help maintain the driving conditions
required for this test.
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 (P1843) is detected, go to AT- 1 7 9 , "
Diagnostic Procedure" .
If DTC (P1752) is detected, go to AT- 1 4 6 , "
Diagnostic Procedure" .
Item name Condition Display value (ON-OFF display)
ATF PRES SW 3Input clutch engaged. Refer to AT- 2 1
.ON
Input clutch disengaged. Refer to AT- 2 1
. OFF
BCIA0030E

DTC P1843 ATF PRESSURE SWITCH 3
AT-179
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Revision: August 20072004 QX56
Diagnostic ProcedureUCS002HZ
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 3”.
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 8 , "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.
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)
ATF PRES
SW 3Input clutch engaged. Refer to AT-2 1
.ON
Input clutch disengaged. Refer to AT-2 1
.OFFPCIA0067E

DTC P1845 ATF PRESSURE SWITCH 5
AT-181
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Revision: August 20072004 QX56
DTC P1845 ATF PRESSURE SWITCH 5PFP:25240
DescriptionUCS002I0
Fail-safe function to detect direct clutch solenoid valve condition.
CONSULT-II Reference ValueUCS002I1
On Board Diagnosis LogicUCS002I2

This is not an OBD-II self-diagnostic item.

Diagnostic trouble code “ATF PRES SW 5/CIRC” with CONSULT-II is detected when TCM detects that
actual gear ratio is normal, and relation between gear position and condition of ATF pressure switch 5 is
irregular during depressing accelerator pedal. (Other than during shift change)
Possible CauseUCS002I3

ATF pressure switch 5

Harness or connectors
(The switch circuit is open or shorted.)
DTC Confirmation ProcedureUCS002I4
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.
ACCELE POS: 1.5/8 - 2.0/8
Selector lever: “D” position
Gear position: 1st

2nd Gear (D/C ON/OFF)
Driving location: Driving the vehicle uphill (increased
engine load) will help maintain the driving conditions
required for this test.
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 (P1845) is detected, go to AT-182, "
Diagnostic Procedure" .
If DTC (P1762) is detected, go to AT-158, "
Diagnostic Procedure" .
Item name Condition Display value (ON-OFF display)
ATF PRES SW 5Direct clutch engaged. Refer to AT- 2 1
.ON
Direct clutch disengaged. Refer to AT- 2 1
. OFF
BCIA0030E

AT-182
DTC P1845 ATF PRESSURE SWITCH 5
Revision: August 20072004 QX56
Diagnostic ProcedureUCS002I5
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 (1st

2nd gear), and confirm
the ON/OFF actuation of the “ATF PRES SW 5”.
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-181, "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)
ATF PRES
SW 5Direct clutch egaged. Refer to AT-2 1
.ON
Direct clutch disegaged. Refer to AT-2 1
.OFFPCIA0067E

AT-184
DTC P1846 ATF PRESSURE SWITCH 6
Revision: August 20072004 QX56
DTC P1846 ATF PRESSURE SWITCH 6PFP:25240
DescriptionUCS002I6
Fail-safe function to detect high and low reverse clutch solenoid valve condition.
CONSULT-II Reference ValueUCS002I7
On Board Diagnosis LogicUCS002I8

This is not an OBD-II self-diagnostic item.

Diagnostic trouble code “ATF PRES SW 6/CIRC” with CONSULT-II is detected when TCM detects that
actual gear ratio is normal, and relation between gear position and condition of ATF pressure switch 6 is
irregular during depressing accelerator pedal. (Other than during shift change)
Possible CauseUCS002I9

ATF pressure switch 6

Harness or connectors
(The switch circuit is open or shorted.)
DTC Confirmation ProcedureUCS002IA
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.
ACCELE POS: 1.5/8 - 2.0/8
Selector lever: “D” position
Gear position: 2nd

3rd Gear (HLR/C ON/OFF)
Driving location: Driving the vehicle uphill (increased
engine load) will help maintain the driving conditions
required for this test.
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 (P1846) is detected, go to AT- 1 8 5 , "
Diagnostic Procedure" .
If DTC (P1767) is detected, go to AT- 1 6 4 , "
Diagnostic Procedure" .
Item name Condition Display value (ON-OFF display)
ATF PRES SW 6High and low reverse clutch engaged. Refer to AT- 2 1
.ON
High and low reverse clutch disengaged. Refer to AT- 2 1
. OFF
BCIA0030E