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Tim West
Tim West, ASE Certified Technician
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2 codes on a 98 nissan maxima 3.0, P0450, EVAP sytem pressure

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2 codes on a 98 nissan maxima 3.0, P0450, EVAP sytem pressure sensor, and
P0141 rear heated o2 Sensor. does one have to do with the other? Is it more times than not the evap sensor or the canister, please help!
Thanks for visiting Just Answer,
These are 2 different problems.
The p0450 - canister purge valve/ vent solenoid. click heregraphicgraphic

p0141 - o2 sensor REAR B1S2

1. Check for battery voltage to the rear O2 sensor on the Red/Black wire (harness side color) with the key ON.

2. Check the ground for the right bank rear O2 sensor heater on the Red wire (harness side color). The Engine Control Module (ECM) should ground the rear O2 sensor heater with engine RPM below 3600 RPM. If the ECM is not grounding the rear O2 sensor, try clearing the code and see if the ECM will attempt to ground the rear O2 sensor heater then.

3. Unplug the rear O2 sensor and ohm the rear O2 sensor heater across the two wires on the rear O2 sensor side of the connector that match up with the Red/Black and Red wires on the harness side of the connector - resistance specification is 2.3 - 4.3 ohms but have seen some Nissan O2 sensor heaters closer to 6.0 ohms.

4. Ground the right bank rear O2 sensor heater at the ECM through an ammeter to ground by back probing one lead of the ammeter into the Red wire at terminal 107 of the ECM and turn the key on and ground the other lead of the ammeter and measure the current flow - look for around 2.0 - 6.0 amps.

5. Check the ECM pin terminal connections for being clean and tight.

6. Check the ECM grounds - look for 0.0


5 volts or less on all.
Customer: replied 6 years ago.
A little confused on the click here link, your saying i should check the lines and canister components for nests, or replace the canister purge valve vent solenoid? the evap Control system pressure sensor is fine? o2 sensor information great!!
Well, the click here was a TSB that may apply to you. Not sure if it will, but it covers some of the code.

The EVAP pressure sensor is a rare cause for this code.


Notes




COMPONENT DESCRIPTION
The EVAP control system pressure sensor is installed in the purge line. The sensor detects the pressure inside the purge line and modifies the voltage signal sent from the ECM. The modified signal will then be returned to the ECM as an input voltage signal. As the pressure increases, the voltage rises. The EVAP control system pressure sensor is not directly used to control the engine system. It is used only for on board diagnosis.



CONSULT REFERENCE VALUE IN DATA MONITOR MODE
Specification data are reference values.



ECM TERMINALS AND REFERENCE VALUE
Specification data are reference values, and are measured between each terminal and (25) (ECCS ground).



ON BOARD DIAGNOSIS LOGIC

DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCEDURE

NOTE: If "DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCEDURE" has been previously conducted, always turn ignition switch "OFF" and wait at least 5 seconds before conducting the next test.

TESTING CONDITION:
Always perform test at a temperature of 5°C (41°F) or more.

With CONSULT

(1) Start engine and warm it up to normal operating temperature.
(2) Check that tank fuel temperature is above 0°C (32°F).
(3) Turn ignition switch "OFF" and wait at least 5 seconds.
(4) Turn ignition switch "ON".
(5) Select "DATA MONITOR" mode with CONSULT
(6) Wait at least 10 seconds.



Electrical Diagrams



Circuit Connectors

1 Of 2

2 Of 2


DIAGNOSTIC PROCEDURE




COMPONENT INSPECTION
EVAP control system pressure sensor

  1. Remove EVAP control system pressure sensor from bracket with its harness connector connected.
  2. Remove hose from EVAP control system pressure sensor.
  3. Apply vacuum and pressure to EVAP control system pressure sensor with pump as shown in figure.
  4. Check output voltage between terminal (52) and (25) (ECM ground). CAUTION:
    • Always calibrate the vacuum pump gauge when using it.
    • Do not apply below -20 kPa (-150 mmHg, -5.91 inHg) or over 20 kPa (150 mmHg, 5.91 inHg) of pressure.
  1. If NG, replace EVAP control system pressure sensor.



 



1. With the Evaporative (EVAP) emission system pressure sensor plugged in and back probing, check the EVAP system pressure sensor output voltage on the White (W) wire with the key on. Should be 3.3 volts key on engine off. If the voltage is low (0.5 to 1.0 volts), disconnect the vacuum line. If the voltage goes up to 3.3, then there is a problem in the canister, most likely the canister vent control valve is stuck closed not allowing the canister to vent. (go to test 5)

2. Check voltages (back probing) on the Red (R) wire at the Evaporative (EVAP) emission system pressure sensor. Key on engine off voltage should be 5.0 (reference voltage).

3. Check the Black (B) ground wire for voltage. Should be near 0.0.

4. Applying a vacuum to the EVAP pressure sensor while watching the voltage, the voltage should decrease while applying vacuum. At 2.3 inches of vacuum applied, the output voltage would normally read approximately 0.5 volts on the White wire.

5. The canister vent control valve is located on the end of the canister. At the 2-pin connector on the canister vent control valve there is battery voltage key on engine off and the ground circuit back to the ECM. This is a normally open valve and the ECM grounds the Black wire to close it. Remove the canister vent control valve and bench test, first, checking to see if it's stuck closed, then apply a power and a ground while blowing through the valve. Test it many times, as it could have an intermittent problem either electrically or mechanically.
Well, the click here was a TSB that may apply to you. Not sure if it will, but it covers some of the code.

The EVAP pressure sensor is a rare cause for this code.


Notes




COMPONENT DESCRIPTION
The EVAP control system pressure sensor is installed in the purge line. The sensor detects the pressure inside the purge line and modifies the voltage signal sent from the ECM. The modified signal will then be returned to the ECM as an input voltage signal. As the pressure increases, the voltage rises. The EVAP control system pressure sensor is not directly used to control the engine system. It is used only for on board diagnosis.



CONSULT REFERENCE VALUE IN DATA MONITOR MODE
Specification data are reference values.



ECM TERMINALS AND REFERENCE VALUE
Specification data are reference values, and are measured between each terminal and (25) (ECCS ground).



ON BOARD DIAGNOSIS LOGIC

DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCEDURE

NOTE: If "DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCEDURE" has been previously conducted, always turn ignition switch "OFF" and wait at least 5 seconds before conducting the next test.

TESTING CONDITION:
Always perform test at a temperature of 5°C (41°F) or more.

With CONSULT

(1) Start engine and warm it up to normal operating temperature.
(2) Check that tank fuel temperature is above 0°C (32°F).
(3) Turn ignition switch "OFF" and wait at least 5 seconds.
(4) Turn ignition switch "ON".
(5) Select "DATA MONITOR" mode with CONSULT
(6) Wait at least 10 seconds.



Electrical Diagrams



Circuit Connectors

1 Of 2

2 Of 2


DIAGNOSTIC PROCEDURE




COMPONENT INSPECTION
EVAP control system pressure sensor

  1. Remove EVAP control system pressure sensor from bracket with its harness connector connected.
  2. Remove hose from EVAP control system pressure sensor.
  3. Apply vacuum and pressure to EVAP control system pressure sensor with pump as shown in figure.
  4. Check output voltage between terminal (52) and (25) (ECM ground). CAUTION:
    • Always calibrate the vacuum pump gauge when using it.
    • Do not apply below -20 kPa (-150 mmHg, -5.91 inHg) or over 20 kPa (150 mmHg, 5.91 inHg) of pressure.
  1. If NG, replace EVAP control system pressure sensor.



 



1. With the Evaporative (EVAP) emission system pressure sensor plugged in and back probing, check the EVAP system pressure sensor output voltage on the White (W) wire with the key on. Should be 3.3 volts key on engine off. If the voltage is low (0.5 to 1.0 volts), disconnect the vacuum line. If the voltage goes up to 3.3, then there is a problem in the canister, most likely the canister vent control valve is stuck closed not allowing the canister to vent. (go to test 5)

2. Check voltages (back probing) on the Red (R) wire at the Evaporative (EVAP) emission system pressure sensor. Key on engine off voltage should be 5.0 (reference voltage).

3. Check the Black (B) ground wire for voltage. Should be near 0.0.

4. Applying a vacuum to the EVAP pressure sensor while watching the voltage, the voltage should decrease while applying vacuum. At 2.3 inches of vacuum applied, the output voltage would normally read approximately 0.5 volts on the White wire.

5. The canister vent control valve is located on the end of the canister. At the 2-pin connector on the canister vent control valve there is battery voltage key on engine off and the ground circuit back to the ECM. This is a normally open valve and the ECM grounds the Black wire to close it. Remove the canister vent control valve and bench test, first, checking to see if it's stuck closed, then apply a power and a ground while blowing through the valve. Test it many times, as it could have an intermittent problem either electrically or mechanically.































































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