Infiniti QX56 (JA60). Manual - part 423

 

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Infiniti QX56 (JA60). Manual - part 423

 

 

EC-344

< COMPONENT DIAGNOSIS >

[VK56DE]

P1572 ASCD BRAKE SWITCH

P1572 ASCD BRAKE SWITCH

Component Description

INFOID:0000000005149404

When the brake pedal is depressed, ASCD brake switch is turned

OFF and stop lamp switch is turned ON. ECM detects the state of

the brake pedal by this input of two kinds (ON/OFF signal).

Refer to 

EC-33, "System Description"

 for the ASCD function.

On Board Diagnosis Logic

INFOID:0000000005149405

• This self-diagnosis has the one trip detection logic.

• The MIL will not light up for this self-diagnosis.

NOTE:

• If DTC P 1572 is displayed with DTC P0605, first perform the trouble diagnosis for DTC P0605. Refer

to 

EC-286, "On Board Diagnosis Logic"

.

• This self-diagnosis has the one trip detection logic. When malfunction A is detected, DTC is not

stored in ECM memory. And in that case, 1st trip DTC and 1st trip freeze frame data are displayed.

1st trip DTC is erased when ignition switch OFF. And even when malfunction A is detected in two

consecutive trips, DTC is not stored in ECM memory.

DTC Confirmation Procedure

INFOID:0000000005149406

CAUTION:

Always drive vehicle at a safe speed.

NOTE:

• Procedure for malfunction B is not described here. It takes extremely long time to complete procedure for

malfunction B. By performing procedure for malfunction A, the incident that causes malfunction B can be

detected. 

• If DTC Confirmation Procedure has been previously conducted, always perform the following procedure

before conducting the next step.

1. Turn ignition switch OFF and wait at least 10 seconds.
2. Turn ignition switch ON.
3. Turn ignition switch OFF and wait at least 10 seconds.
TESTING CONDITION:

Steps 3 and 6 may be conducted with the drive wheels lifted in the shop or by driving the vehicle. If a

road test is expected to be easier, it is unnecessary to lift the vehicle.

1. Start engine (VDC switch OFF).

2. Press MAIN switch and make sure that CRUISE indicator lights up.

3. Drive the vehicle for at least 5 consecutive seconds under the following condition.

BBIA0373E

DTC No.

Trouble Diagnosis 

Name

DTC Detecting Condition

Possible Cause

P1572
1572

ASCD brake switch

A)

When the vehicle speed is above 30km/h (19 
MPH), ON signals from the stop lamp switch 
and the ASCD brake switch are sent to ECM 
at the same time.

• Harness or connectors

(The stop lamp switch circuit is shorted.)

• Harness or connectors

(The ASCD brake switch circuit is shorted.)

• Stop lamp switch
• ASCD brake switch
• Incorrect stop lamp switch installation
• Incorrect ASCD brake switch installation
• ECM

B)

ASCD brake switch signal is not sent to ECM 
for extremely long time while the vehicle is 
driving

P1572 ASCD BRAKE SWITCH

EC-345

< COMPONENT DIAGNOSIS >

[VK56DE]

C

D

E

F

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A

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4. Check 1st trip DTC.

5. If 1st trip DTC is detected, go to 

EC-345, "Diagnosis Procedure"

.

If 1st trip DTC is not detected, go to the following step.

6. Drive the vehicle for at least 5 consecutive seconds under the following condition.

7. Check 1st trip DTC.

8. If 1st trip DTC is detected, go to 

EC-345, "Diagnosis Procedure"

.

Diagnosis Procedure

INFOID:0000000005149407

1.

CHECK OVERALL FUNCTION-I

 With CONSULT-III

1. Turn ignition switch ON.

2. Select “BRAKE SW1” in “DATA MONITOR” mode with CONSULT-III.

3. Check “BRAKE SW1” indication under the following conditions.

 Without CONSULT-III

1. Turn ignition switch ON.

2. Check voltage between ECM terminal 108 and ground under the

following conditions.

OK or NG

OK

>> GO TO 2.

NG

>> GO TO 3.

2.

CHECK OVERALL FUNCTION-II

 With CONSULT-III

Check “BRAKE SW2” indication in “DATA MONITOR” mode. 

VHCL SPEED SE

More than 30 km/h (19 MPH)

Selector lever

Suitable position 

VHCL SPEED SE

More than 30 km/h (19 MPH)

Selector lever

Suitable position 

Driving location

Depress the brake pedal for more than 
five seconds so as not to come off from 
the above-mentioned condition.

CONDITION

INDICATION

Brake pedal: Slightly depressed

OFF

Brake pedal: Fully released

ON

CONDITION

VOLTAGE

Brake pedal: Slightly depressed

Approximately 0V

Brake pedal: Fully released

Battery voltage

MBIB0061E

CONDITION

INDICATION

Brake pedal: Fully released

OFF

Brake pedal: Slightly depressed

ON

EC-346

< COMPONENT DIAGNOSIS >

[VK56DE]

P1572 ASCD BRAKE SWITCH

 Without CONSULT-III

Check voltage between ECM terminal 101 and ground under the following conditions.

OK or NG

OK

>> GO TO 11.

NG

>> GO TO 7.

3.

CHECK ASCD BRAKE SWITCH POWER SUPPLY CIRCUIT

1. Turn ignition switch OFF.

2. Disconnect ASCD brake switch harness connector.

3. Turn ignition switch ON.

4. Check voltage between ASCD brake switch terminal 1 and

ground with CONSULT-III or tester.

OK or NG

OK

>> GO TO 5.

NG

>> GO TO 4.

4.

DETECT MALFUNCTIONING PART

Check the following.

• Harness connectors M31, E152

• Fuse block (J/B) connector M4

• 10 A fuse (No. 15)

• Harness for open or short between ASCD brake switch and fuse

>> Repair open circuit or short to ground or short to power in harness or connectors.

5.

CHECK ASCD BRAKE SWITCH INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT

1. Turn ignition switch OFF.

2. Disconnect ECM harness connector.

3. Check harness continuity between ECM terminal 108 and ASCD brake switch terminal 2.

Refer to Wiring Diagram.

CONDITION

VOLTAGE

Brake pedal: Fully released

Approximately 0V

Brake pedal: Slightly depressed

Battery voltage

PBIB1537E

BBIA0373E

Voltage: Battery voltage

PBIB0857E

P1572 ASCD BRAKE SWITCH

EC-347

< COMPONENT DIAGNOSIS >

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4. Also check harness for short to ground and short to power.
OK or NG

OK

>> GO TO 6.

NG

>> Repair open circuit or short to ground or short to power in harness or connectors.

6.

CHECK ASCD BRAKE SWITCH

Refer to 

EC-348, "Component Inspection"

.

OK or NG

OK

>> GO TO 11.

NG

>> Replace ASCD brake switch.

7.

CHECK STOP LAMP SWITCH POWER SUPPLY CIRCUIT

1. Turn ignition switch OFF.

2. Disconnect stop lamp switch harness connector.

3. Check voltage between stop lamp switch terminal 3 and ground

with CONSULT-III or tester.

OK or NG

OK

>> GO TO 9.

NG

>> GO TO 8.

8.

DETECT MALFUNCTIONING PART

Check the following.

• Harness connectors M31, E152

• Fuse block (J/B) connector M60

• 10 A fuse (No. 20)

• Harness for open or short between stop lamp switch and battery

>> Repair open circuit or short to ground or short to power in harness or connectors.

9.

CHECK STOP LAMP SWITCH INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT

1. Disconnect ECM harness connector.

2. Check harness continuity between ECM terminal 101 and stop lamp switch terminal 4.

Refer to Wiring Diagram.

3. Also check harness for short to ground and short to power.
OK or NG

OK

>> GO TO 10.

Continuity should exist.

BBIA0373E

Voltage: Battery voltage

PBIB2102E

Continuity should exist.

 

 

 

 

 

 

 

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