Power steering pressure (PSP) sensor (1) 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:0000000003936710

The MIL will not illuminate for this self-diagnosis.
NOTE:
If DTC P0550 is displayed with DTC P0643, first perform the trouble diagnosis for DTC P0643. Refer to

EC-775, "DTC Confirmation Procedure"

DTC Confirmation Procedure

INFOID:0000000003936711

If DTC Confirmation Procedure has been previously conducted, always perform the following procedure
before conducting the next step.

Turn ignition switch OFF and wait at least 10 seconds.

Turn ignition switch ON.

Turn ignition switch OFF and wait at least 10 seconds.

Start engine and let it idle for at least 5 seconds.

Check 1st trip DTC.

If 1st trip DTC is detected, go to

EC-767, "Diagnosis Procedure"

Diagnosis Procedure

INFOID:0000000003936712

CHECK GROUND CONNECTIONS

Turn ignition switch OFF.

Loosen and retighten ground screws on the body.
Refer to

EC-568, "Ground Inspection"

OK or NG

>> GO TO 2.

>> Repair or replace ground connections.

ALBIA0361ZZ

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

2009 Pathfinder

EC-768

< COMPONENT DIAGNOSIS >

[VK56DE]

P0550 PSP SENSOR

CHECK PSP SENSOR POWER SUPPLY CIRCUIT

Disconnect power steering pressure (PSP) sensor (1) harness
connector.

Turn ignition switch ON.

Check voltage between PSP sensor terminal 1 and ground with
CONSULT-III or tester.

OK or NG

>> GO TO 3.

>> Repair harness or connectors.

CHECK PSP SENSOR GROUND CIRCUIT FOR OPEN AND SHORT

Turn ignition switch OFF.

Disconnect ECM harness connector.

Check harness continuity between PSP sensor terminal 3 and ECM terminal 67.
Refer to Wiring Diagram.

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

OK or NG

>> GO TO 4.

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

CHECK PSP SENSOR INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT

Check harness continuity between ECM terminal 12 and PSP sensor terminal 2.

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

OK or NG

>> GO TO 5.

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

CHECK PSP SENSOR

Refer to

EC-769, "Component Inspection"

OK or NG

>> GO TO 6.

>> Replace PSP sensor.

CHECK INTERMITTENT INCIDENT

Refer to

GI-49, "Intermittent Incident"

>> INSPECTION END

ALBIA0361ZZ

Voltage: Approximately 5 V

PBIB0188E

Continuity should exist.

2009 Pathfinder

P0550 PSP SENSOR

EC-769

< COMPONENT DIAGNOSIS >

[VK56DE]

Component Inspection

INFOID:0000000003936713

POWER STEERING PRESSURE SENSOR

Reconnect all harness connectors disconnected.

Start engine and let it idle.

Check voltage between ECM terminal 12 and ground under the
following conditions.

Condition

Voltage

Steering wheel: Being turned

0.5 - 4.5V

Steering wheel: Not being turned

0.4 - 0.8V

MBIB0126E

2009 Pathfinder

EC-770

< COMPONENT DIAGNOSIS >

[VK56DE]

P0603 ECM POWER SUPPLY

P0603 ECM POWER SUPPLY

Component Description

INFOID:0000000003936714

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:0000000003936715

DTC Confirmation Procedure

INFOID:0000000003936716

If DTC Confirmation Procedure has been previously conducted, always perform the following procedure
before conducting the next step.

Turn ignition switch OFF and wait at least 10 seconds.

Turn ignition switch ON.

Turn ignition switch OFF and wait at least 10 seconds.

Start engine and let it idle for 1 second.

Turn ignition switch OFF, wait at least 10 seconds and then turn it ON.

Repeat steps 2 to 3 for 4 times.

Check 1st trip DTC.

If 1st trip DTC is detected, go to

EC-770, "Diagnosis Procedure"

Diagnosis Procedure

INFOID:0000000003936717

CHECK ECM POWER SUPPLY

Turn ignition switch OFF.

Disconnect ECM harness connector.

Check voltage between ECM terminal 121 and ground with
CONSULT-III or tester.

OK or NG

>> GO TO 3.

>> GO TO 2.

DETECT MALFUNCTIONING PART

Check the following.

PBIB1164E

DTC No.

Trouble diagnosis name

DTC detecting condition

Possible cause

P0603
0603

ECM power supply circuit

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

MBIB0026E

2009 Pathfinder

P0603 ECM POWER SUPPLY

EC-771

< COMPONENT DIAGNOSIS >

[VK56DE]

• IPDM E/R connector E121
• 20 A fuse (No. 53)
• Harness for open or short between ECM and battery

>> Repair or replace harness or connectors.

CHECK INTERMITTENT INCIDENT

Refer to

GI-49, "Intermittent Incident"

OK or NG

>> GO TO 4.

>> Repair or replace harness or connectors.

PERFORM DTC CONFIRMATION PROCEDURE

Turn ignition switch ON.

Erase DTC. Refer to

EC-525, "Emission-related Diagnostic Information"

Perform DTC Confirmation Procedure. Refer to

EC-770, "DTC Confirmation Procedure"

Is the 1st trip DTC P0603 displayed again?

Yes or No

Yes

>> GO TO 5.

>> INSPECTION END

REPLACE ECM

Replace ECM.

Perform initialization of NVIS(NATS) system and registration of all NVIS(NATS) ignition key IDs. Refer to

SEC-8, "ECM RE-COMMUNICATING FUNCTION : Special Repair Requirement"

(with intelligent key sys-

tem) or

SEC-124, "ECM RE-COMMUNICATING FUNCTION : Special Repair Requirement"

(without intel-

ligent key system).

Perform

EC-499, "VIN Registration"

Perform

EC-500, "Accelerator Pedal Released Position Learning"

Perform

EC-500, "Throttle Valve Closed Position Learning"

Perform

EC-500, "Idle Air Volume Learning"

>> INSPECTION END

2009 Pathfinder

EC-772

< COMPONENT DIAGNOSIS >

[VK56DE]

P0605 ECM

P0605 ECM

Component Description

INFOID:0000000003936718

The ECM consists of a microcomputer and connectors for signal
input and output and for power supply. The ECM controls the engine.

On Board Diagnosis Logic

INFOID:0000000003936719

This self-diagnosis has one or two trip detection logic.

FAIL-SAFE MODE

ECM enters fail-safe mode when the malfunction A is detected.

DTC Confirmation Procedure

INFOID:0000000003936720

Perform PROCEDURE FOR MALFUNCTION A first. If the 1st trip DTC cannot be confirmed, perform
PROCEDURE FOR MALFUNCTION B. If there is no malfunction on PROCEDURE FOR MALFUNCTION
B, perform PROCEDURE FOR MALFUNCTION C.
NOTE:
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.

Turn ignition switch ON.

Turn ignition switch OFF and wait at least 10 seconds.

PROCEDURE FOR MALFUNCTION A

Turn ignition switch ON.

Check 1st trip DTC.

If 1st trip DTC is detected, go to

EC-773, "Diagnosis Procedure"

PROCEDURE FOR MALFUNCTION B

Turn ignition switch ON and wait at least 1 second.

Turn ignition switch OFF, wait at least 10 seconds and then turn it ON.

Check 1st trip DTC.