Infiniti QX56 (JA60). Manual - part 947

TM-90

< COMPONENT DIAGNOSIS >

P1772 LOW COAST BRAKE SOLENOID

P1772 LOW COAST BRAKE SOLENOID

Description

INFOID:0000000005148666

Low coast brake solenoid valve is turned “ON” or “OFF” by the TCM in response to signals sent from the trans-

mission range switch, output speed sensor and accelerator pedal position sensor. Gears will then be shifted to

the optimum position.

CONSULT-III Reference Value in Data Monitor Mode

INFOID:0000000005148667

On Board Diagnosis Logic

INFOID:0000000005148668

• This is an OBD-II self-diagnostic item.

• Diagnostic trouble code “P1772 L C BRAKE SOLENOID” with CONSULT-III is detected when TCM detects

an improper voltage drop when it tries to operate the solenoid valve.

Possible Cause

INFOID:0000000005148669

• Harness or connectors

(The solenoid circuit is open or shorted.)

• Low coast brake solenoid valve 

DTC Confirmation Procedure

INFOID:0000000005148670

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-III

1. Turn ignition switch “ON”. (Do not start engine.)

2. Select “DATA MONITOR” mode for “ENGINE” with CONSULT-III.

3. Start engine.

4. Drive vehicle and maintain the following conditions for at least 5 consecutive seconds.

SLCT LVR POSI: “1” or “2”

GEAR: “1st” or “2nd” (LC/B ON/OFF)

5. If DTC is detected, go to 

TM-90, "Diagnosis Procedure"

.

 WITH GST

Follow the procedure “With CONSULT-III”.

Diagnosis Procedure

INFOID:0000000005148671

1.

CHECK INPUT SIGNAL

With CONSULT-III

1. Turn ignition switch “ON”.

2. Select “SELECTION FROM MENU” in “DATA MONITOR” mode for “TRANSMISSION” with CONSULT-III.

3. Start the engine.

4. Read out the value of “ON OFF SOL” while driving.

OK or NG

OK

>> GO TO 4.

Item name

Condition 

Display value

ON OFF SOL

Low coast brake engaged. Refer to 

TM-9

.

ON

Low coast brake disengaged. Refer to 

TM-9

.

OFF

Item name

Condition 

Display value

ON OFF SOL

Low coast brake engaged. Refer to 

TM-9

.

ON

Low coast brake disengaged. Refer to 

TM-9

.

OFF

P1772 LOW COAST BRAKE SOLENOID

TM-91

< COMPONENT DIAGNOSIS >

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NG

>> GO TO 2.

2.

CHECK TCM POWER SUPPLY AND GROUND CIRCUIT

Check TCM power supply and ground circuit. Refer to 

TM-94, "Diagnosis Procedure"

.

OK or NG

OK

>> GO TO 3.

NG

>> Repair or replace damaged parts.

3.

DETECT MALFUNCTIONING ITEM

Check the following items:

• The A/T assembly harness connector pin terminals for damage or loose connection with harness connector.
OK or NG

OK

>> Replace the control valve with TCM. Refer to 

TM-172, "Control Valve with TCM and A/T Fluid

Temperature Sensor 2 and Plug"

.

NG

>> Repair or replace damaged parts.

4.

CHECK DTC

Perform “DTC Confirmation Procedure”.

• Refer to 

TM-90, "DTC Confirmation Procedure"

.

OK or NG

OK

>> INSPECTION END

NG

>> GO TO 2.

TM-92

< COMPONENT DIAGNOSIS >

P1774 LOW COAST BRAKE SOLENOID

P1774 LOW COAST BRAKE SOLENOID

Description

INFOID:0000000005148672

• Low coast brake solenoid valve is turned “ON” or “OFF” by the TCM in response to signals sent from the

transmission rang switch, output speed sensor and accelerator pedal 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 malfunc-

tion such as control valve sticking, improper solenoid valve operation.

CONSULT-III Reference Value in Data Monitor Mode

INFOID:0000000005148673

On Board Diagnosis Logic

INFOID:0000000005148674

• This is an OBD-II self-diagnostic item.

• Diagnostic trouble code “P1774 L C BRAKE SOLENOID” with CONSULT-III 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 Cause

INFOID:0000000005148675

• Harness or connectors

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

• Low coast brake solenoid valve 

• ATF pressure switch 2

DTC Confirmation Procedure

INFOID:0000000005148676

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-III

1. Start engine.

2. Accelerate vehicle to maintain the following conditions. 

SLCT LVR POSI: “1” or “2” position 

GEAR: “1st” or “2nd” (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 “TRANSMISSION” with CONSULT-III. If DTC (P1774) is

detected, refer to 

TM-93, "Diagnosis Procedure"

.

If DTC (P1772) is detected, go to 

TM-90, "Diagnosis Procedure"

.

 WITH GST

Follow the procedure “With CONSULT-III”.

Item name

Condition 

Display value

ON OFF SOL

Low coast brake engaged. Refer to 

TM-9

.

ON

Low coast brake disengaged. Refer to 

TM-9

.

OFF

ATF PRES SW 2

Low coast brake engaged. Refer to 

TM-9

.

ON

Low coast brake disengaged. Refer to 

TM-9

.

OFF

P1774 LOW COAST BRAKE SOLENOID

TM-93

< COMPONENT DIAGNOSIS >

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E

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Diagnosis Procedure

INFOID:0000000005148677

1.

CHECK INPUT SIGNALS

With CONSULT-III

1. Start the engine.

2. Select “SELECTION FROM MENU” in “DATA MONITOR” mode for “TRANSMISSION” with CONSULT-III.

3. Drive vehicle in the “1” or “2” position (“1

1

” or “2

2

” gear) and confirm the ON/OFF actuation of the “ATF

PRES SW 2” and “ON OFF SOL”.

OK or NG

OK

>> GO TO 4.

NG

>> GO TO 2.

2.

CHECK TCM POWER SUPPLY AND GROUND CIRCUIT

Check TCM power supply and ground circuit. Refer to 

TM-94, "Diagnosis Procedure"

.

OK or NG

OK

>> GO TO 3.

NG

>> Repair or replace damaged parts.

3.

DETECT MALFUNCTIONING ITEM

Check the following items:

• The A/T assembly harness connector pin terminals for damage or loose connection with harness connector.
OK or NG

OK

>> Replace the control valve with TCM. Refer to 

TM-172, "Control Valve with TCM and A/T Fluid

Temperature Sensor 2 and Plug"

.

NG

>> Repair or replace damaged parts.

4.

CHECK DTC

Perform “DTC Confirmation Procedure”.

• Refer to 

TM-92, "DTC Confirmation Procedure"

.

OK or NG

OK

>> INSPECTION END

NG

>> GO TO 2.

Item name

Condition 

Display value

ON OFF SOL

Low coast brake engaged. Refer to 

TM-9

.

ON

Low coast brake disengaged. Refer to 

TM-9

.

OFF

ATF PRES SW 2

Low coast brake engaged. Refer to 

TM-9

.

ON

Low coast brake disengaged. Refer to 

TM-9

.

OFF