Nissan Xterra. Manual - part 308

EC-358

< DTC/CIRCUIT DIAGNOSIS >

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P0550 PSP SENSOR

P0550 PSP SENSOR

Component Description

INFOID:0000000009484073

Power steering pressure (PSP) sensor is installed to the power

steering high-pressure tube and detects a power steering load. This

sensor is a potentiometer which transforms the power steering load

into output voltage, and emits the voltage signal to the ECM. The

ECM controls the electric throttle control actuator and adjusts the

throttle valve opening angle to increase the engine speed and

adjusts the idle speed for the increased load.

On Board Diagnosis Logic

INFOID:0000000009484074

The MIL will not illuminate for this diagnosis.

NOTE:

If DTC P0550 is displayed with DTC P0643, first perform the trouble diagnosis for DTC P0643. Refer to

EC-366

.

DTC Confirmation Procedure

INFOID:0000000009484075

1. If DTC Confirmation Procedure has been previously conducted, always perform the following before con-

ducting the next step.

a. Turn ignition switch OFF and wait at least 10 seconds.
b. Turn ignition switch ON.
c.

Turn ignition switch OFF and wait at least 10 seconds.

2. Start engine and let it idle for at least 5 seconds.
3. Check 1st trip DTC.
4. If 1st trip DTC is detected, go to 

EC-358, "Diagnosis Procedure"

.

Diagnosis Procedure

INFOID:0000000009484076

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.

BBIA0552E

DTC No.

Trouble diagnosis name

DTC detecting condition

Possible cause

P0550
0550

Power steering pressure 
sensor circuit

An excessively low or high voltage from the 
sensor is sent to ECM.

• Harness or connectors

(The sensor circuit is open or shorted)

• Power steering pressure sensor

BBIA0539E

P0550 PSP SENSOR

EC-359

< DTC/CIRCUIT DIAGNOSIS >

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CHECK PSP SENSOR POWER SUPPLY CIRCUIT

1. Disconnect power steering pressure (PSP) sensor harness con-

nector.

2. Turn ignition switch ON.

3. Check voltage between PSP sensor terminal 3 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 PSP SENSOR GROUND CIRCUIT FOR OPEN AND SHORT

1. Turn ignition switch OFF.

2. Disconnect ECM harness connector.

3. Check harness continuity between PSP sensor terminal 1 and ECM terminal 72.

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 PSP SENSOR INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT

1. Check harness continuity between ECM terminal 65 and PSP sensor terminal 2.

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

Refer to 

EC-359, "Component Inspection"

.

OK or NG

OK

>> GO TO 6.

NG

>> Replace PSP sensor. Refer to 

ST-19, "Removal and Installation"

.

6.

CHECK INTERMITTENT INCIDENT

Refer to 

GI-40, "Intermittent Incident"

.

>> INSPECTION END

Component Inspection

INFOID:0000000009484077

POWER STEERING PRESSURE SENSOR

1. Reconnect all harness connectors disconnected.
2. Start engine and let it idle.
3. Check voltage between ECM terminal 65 and ground under the following conditions.

Voltage: Approximately 5V

BBIA0552E

Continuity should exist.

Continuity should exist.

EC-360

< DTC/CIRCUIT DIAGNOSIS >

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P0550 PSP SENSOR

Condition

Voltage

Steering wheel: being turned

0.5 - 4.5V

Steering wheel: not being turned

0.4 - 0.8V

P0603 ECM POWER SUPPLY

EC-361

< DTC/CIRCUIT DIAGNOSIS >

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P0603 ECM POWER SUPPLY

Component Description

INFOID:0000000009484078

Battery voltage is supplied to the ECM even when the ignition switch

is turned OFF for the ECM memory function of the DTC memory, the

air-fuel ratio feedback compensation value memory, the idle air vol-

ume learning value memory, etc.

On Board Diagnosis Logic

INFOID:0000000009484079

DTC Confirmation Procedure

INFOID:0000000009484080

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

before conducting the next step.

a. Turn ignition switch OFF and wait at least 10 seconds.
b. Turn ignition switch ON.
c. Turn ignition switch OFF and wait at least 10 seconds.
2. Turn ignition switch ON, wait at least 10 seconds.
3. Turn ignition switch OFF, wait at least 5 minutes.
4. Turn ignition switch ON, wait at least 10 seconds.
5. Repeat steps 2 to 3 for 5 times.
6. Check 1st trip DTC.
7. If 1st trip DTC is detected, go to 

EC-361, "Diagnosis Procedure"

.

Diagnosis Procedure

INFOID:0000000009484081

1.

CHECK ECM POWER SUPPLY

1. Turn ignition switch OFF.

2. Disconnect ECM harness connector.

3. Check voltage between ECM terminal 26 and ground with CONSULT or tester.

OK or NG

OK

>> GO TO 3.

NG

>> GO TO 2.

2.

DETECT MALFUNCTIONING PART

Check the following.

• Harness connector F32, E2

• 20 A fuse (No. 53)

• IPDM E/R harness connector E121

• Harness for open or short between ECM and battery

PBIB1164E

DTC No.

Trouble diagnosis name

DTC detecting condition

Possible cause

P0603
0603

ECM power supply cir-
cuit

ECM back up RAM system does not function 
properly.

• Harness or connectors

[ECM power supply (back up) circuit is 
open or shorted.]

• ECM

Voltage: Battery voltage