Nissan Xterra. Manual - part 328

EC-438

< DTC/CIRCUIT DIAGNOSIS >

[VQ40DE]

P2122, P2123 APP SENSOR

Diagnosis Procedure

INFOID:0000000009484192

1.

CHECK GROUND CONNECTIONS

1. Turn ignition switch OFF.

2. Loosen and retighten three ground screws on the body. Refer to 

EC-152, "Ground Inspection"

.

OK or NG

OK

>> GO TO 2.

NG

>> Repair or replace ground connections.

2.

CHECK APP SENSOR 1 POWER SUPPLY CIRCUIT

1. Disconnect accelerator pedal position (APP) sensor harness connector.

2. Turn ignition switch ON.

3. Check voltage between APP sensor terminal 2 and ground with CONSULT or tester.

OK or NG

OK

>> GO TO 3.

NG

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

3.

CHECK APP SENSOR 1 GROUND CIRCUIT FOR OPEN AND SHORT

1. Turn ignition switch OFF.

2. Disconnect ECM harness connector.

3. Check harness continuity between APP sensor terminal 4 and ECM terminal 100.

Refer to Wiring Diagram.

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

OK

>> GO TO 4.

NG

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

4.

CHECK APP SENSOR INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT

1. Check harness continuity between ECM terminal 97 and APP sensor terminal 3.

Refer to Wiring Diagram.

2. Also check harness for short to ground and short to power.

BBIA0539E

Voltage: Approximately 5V

BBIA0556E

Continuity should exist.

Continuity should exist.

P2122, P2123 APP SENSOR

EC-439

< DTC/CIRCUIT DIAGNOSIS >

[VQ40DE]

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OK or NG

OK

>> GO TO 5.

NG

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

5.

CHECK APP SENSOR

Refer to 

EC-439, "Component Inspection"

.

OK or NG

OK

>> GO TO 7.

NG

>> GO TO 6.

6.

REPLACE ACCELERATOR PEDAL ASSEMBLY

1. Replace accelerator pedal assembly. Refer to 

ACC-3, "Component"

.

2. Perform 

EC-125, "Accelerator Pedal Released Position Learning"

.

3. Perform 

EC-125, "Throttle Valve Closed Position Learning"

.

4. Perform 

EC-125, "Idle Air Volume Learning"

.

>> INSPECTION END

7.

CHECK INTERMITTENT INCIDENT

Refer to 

GI-40, "Intermittent Incident"

.

>> INSPECTION END

Component Inspection

INFOID:0000000009484193

ACCELERATOR PEDAL POSITION SENSOR

1. Reconnect all harness connectors disconnected.
2. Turn ignition switch ON.
3. Check voltage between ECM terminals 97 (APP sensor 1 signal), 98 (APP sensor 2 signal) and ground

under the following conditions.

4. If NG, replace accelerator pedal assembly and go to next step.
5. Perform 

EC-125, "Accelerator Pedal Released Position Learning"

.

6. Perform 

EC-125, "Throttle Valve Closed Position Learning"

.

7. Perform 

EC-125, "Idle Air Volume Learning"

.

Terminal

Accelerator pedal

Voltage

97
 (Accelerator pedal position 
sensor 1)

Fully released

0.65 - 0.87V

Fully depressed

More than 4.3V

98
(Accelerator pedal position 
sensor 2)

Fully released

0.28 - 0.48V

Fully depressed

More than 2.0V

EC-440

< DTC/CIRCUIT DIAGNOSIS >

[VQ40DE]

P2127, P2128 APP SENSOR

P2127, P2128 APP SENSOR

Component Description

INFOID:0000000009484194

The accelerator pedal position sensor is installed on the upper end

of the accelerator pedal assembly. The sensor detects the accelera-

tor position and sends a signal to the ECM.

Accelerator pedal position sensor has two sensors. These sensors

are a kind of potentiometers which transform the accelerator pedal

position into output voltage, and emit the voltage signal to the ECM.

In addition, these sensors detect the opening and closing speed of

the accelerator pedal and feed the voltage signals to the ECM. The

ECM judges the current opening angle of the accelerator pedal from

these signals and controls the throttle control motor based on these

signals.

Idle position of the accelerator pedal is determined by the ECM

receiving the signal from the accelerator pedal position sensor. The ECM uses this signal for the engine oper-

ation such as fuel cut.

On Board Diagnosis Logic

INFOID:0000000009484195

These self-diagnoses have the one trip detection logic.

FAIL-SAFE MODE

When the malfunction is detected, ECM enters fail-safe mode and the MIL illuminates.

DTC Confirmation Procedure

INFOID:0000000009484196

NOTE:

If DTC Confirmation Procedure has been previously conducted, always perform the following before conduct-

ing 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:

Before performing the following procedure, confirm that battery voltage is more than 10V at idle.
1. Start engine and let it idle for 1 second.
2. Check DTC.
3. If DTC is detected, go to 

EC-440, "Diagnosis Procedure"

.

Diagnosis Procedure

INFOID:0000000009484197

1.

CHECK GROUND CONNECTIONS

1. Turn ignition switch OFF.

PBIB1741E

DTC No.

Trouble diagnosis name

DTC detecting condition

Possible cause

P2127
2127

Accelerator pedal posi-
tion sensor 2 circuit low 
input

An excessively low voltage from the APP sen-
sor 2 is sent to ECM.

• Harness or connectors

(The APP sensor 2 circuit is open or 
shorted.)
(The TP sensor circuit shorted.)

• Accelerator pedal position sensor

(APP sensor 2)

• Electric throttle control actuator

(TP sensor 1 and 2)

P2128
2128

Accelerator pedal posi-
tion sensor 2 circuit high 
input

An excessively high voltage from the APP sen-
sor 2 is sent to ECM.

Engine operating condition in fail-safe mode

The ECM controls the electric throttle control actuator in regulating the throttle opening in order for the idle position to be within +10 
degrees.
The ECM regulates the opening speed of the throttle valve to be slower than the normal condition.
So, the acceleration will be poor. 

P2127, P2128 APP SENSOR

EC-441

< DTC/CIRCUIT DIAGNOSIS >

[VQ40DE]

C

D

E

F

G

H

I

J

K

L

M

A

EC

N

P

O

2. Loosen and retighten three ground screws on the body, Refer to 

EC-152, "Ground Inspection"

.

OK or NG

OK

>> GO TO 2.

NG

>> Repair or replace ground connections.

2.

CHECK APP SENSOR 2 POWER SUPPLY CIRCUIT-I

1. Disconnect accelerator pedal position (APP) sensor harness connector.

2. Turn ignition switch ON.

3. Check voltage between APP sensor terminal 1 and ground with CONSULT or tester.

OK or NG

OK

>> GO TO 7.

NG

>> GO TO 3.

3.

CHECK APP SENSOR 2 POWER SUPPLY CIRCUIT-II

1. Turn ignition switch OFF.

2. Disconnect ECM harness connector.

3. Check harness continuity between APP sensor terminal 1 and ECM terminal 103.

Refer to wiring diagram.

OK or NG

OK

>> GO TO 4.

NG

>> Repair open circuit.

4.

CHECK THROTTLE POSITION SENSOR 2 POWER SUPPLY CIRCUIT-III

Check harness for short to power and short to ground, between the following terminals.

OK or NG

OK

>> GO TO 5.

NG

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

5.

CHECK THROTTLE POSITION SENSOR

BBIA0539E

Voltage: Approximately 5V

BBIA0556E

Continuity should exist.

ECM terminal

Sensor terminal

103

APP sensor terminal 1

24

Electric throttle control actuator terminal 2