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P1451








3MZ-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P1451: Fuel Tank Pressure Sensor Range/Performance

DTC P1451 - Fuel Tank Pressure Sensor Range/Performance

DTC P1452 - Fuel Tank Pressure Sensor Low Input

DTC P1453 - Fuel Tank Pressure Sensor High Input

DTC SUMMARY





DESCRIPTION

While the engine is running, if predetermined conditions (closed loop, etc.) are met, the purge VSV is opened by the ECM (included in the hybrid vehicle control ECU) and stored fuel vapors in the canister are purged to the intake manifold. The ECM will change the duty cycle ratio of the Purge VSV to control purge flow volume.
Purge flow volume is also determined by the intake manifold pressure. Atmospheric pressure is allowed to enter the canister through the vent valve to ensure that purge flow is maintained when negative pressure (vacuum) is applied to the canister.
The ECM monitors the condition of both the key-off monitor and purge flow monitor to ensure proper operation of the EVAP system.





























Key-off monitor

This monitoring system checks for canister pump module malfunctions and leaks from the EVAP and closed tank systems. Be sure to leave the vehicle for at least 5 hours to sufficiently cool the fuel and stabilize fuel tank pressure. This makes EVAP system monitoring more accurate.
HINT: If the engine coolant temperature is 35°C or more, 5 hours after the power switch has been turned off, the ECM (included in the hybrid vehicle control ECU) will begin performing a monitor check after another 2 hours. If the engine coolant temperature is still 35°C or more, 7 hours after the power switch has been turned off, the ECM will begin performing a monitor check after another 2.5 hours.

There are two methods for monitoring the EVAP system.
1. If the fuel tank pressure is higher or lower than the atmospheric pressure, the system determines that there are no leaks in the closed tank system and the system will check for leaks from the piping and canister between the purge VSV and canister pump module. (Method A)
2. If the fuel tank pressure is almost the same as the atmospheric pressure, vacuum will be allowed to enter the fuel tank and the system will check for leaks from the fuel tank after checking for leaks from the canister. (Method B)









HINT: *: If there is only a small amount of fuel in the fuel tank, stabilizing the EVAP pressure takes longer than usual.





Purge flow monitor

If EVAP system pressure change is less than 7.5 mmHg (1 kPa) when the engine is running and the purge VSV is turned ON (closed), the ECM (included in the hybrid vehicle control ECU) determines that the purge flow is insufficient.





MONITOR DESCRIPTION

1. DTC P1451: Pressure sensor abnormal voltage fluctuation or being constant
If the pressure sensor output voltage fluctuates rapidly for 10 seconds, the ECM (included in the hybrid vehicle control ECU) stops the EVAP system monitor. The ECM interprets this as the pressure sensor voltage fluctuating, and stops the EVAP system monitor. The ECM then illuminates the MIL and sets the DTC.
Alternatively, if the sensor output voltage does not change for 10 seconds, the ECM interprets this as the sensor voltage being constant, and stops the monitor. The ECM then illuminates the MIL and sets the DTC.
(Both malfunctions are detected by 2 trip detection logic).





2. DTC P1452: Pressure sensor voltage low
If the pressure sensor output voltage is below 0.45 V, the ECM (included in the hybrid vehicle control ECU) interprets this as an open or short circuit in the pressure sensor or its circuit, and stops the EVAP system monitor. The ECM then illuminates the MIL and sets the DTC (1 trip detection logic).
3. DTC P1453: Pressure sensor voltage high
If the pressure sensor voltage output is 4.9 V or more, the ECM (included in the hybrid vehicle control ECU) interprets this as an open or short circuit in the pressure sensor or its circuit, and stops the EVAP system monitor. The ECM then illuminates the MIL and sets the DTC (1 trip detection logic).

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS

P1451 (Noise Monitor):





Example of restart time





P1451 (Stuck Monitor):





Example of restart time





P1452 and P1453:





TYPICAL MALFUNCTION THRESHOLDS

P1451: Pressure sensor noise





P1451: Pressure sensor stuck





P1452: Pressure sensor low voltage





P1453: Pressure sensor high voltage





WIRING DIAGRAM





INSPECTION PROCEDURE
NOTICE:
- When a vehicle is brought into the workshop, leave it as it is. Do not change the vehicle condition. For example, do not tighten the fuel tank cap.
- Do not disassemble the canister pump module.
- The Techstream is required to conduct the following diagnostic troubleshooting procedure.

PROCEDURE

1. CONFIRM DTC AND FUEL TANK PRESSURE
(a) Connect the Techstream to the DLC3.
(b) Turn the power switch on (IG).
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
(e) Read the DTCs.
(f) Enter the following menus: Powertrain / Engine and ECT / Data List.
(g) Read the EVAP (Evaporative Emission) pressure displayed on the Techstream.
Result:






C -- GO TO EVAP INSPECTION PROCEDURE
B -- CHECK HARNESS AND CONNECTOR (FUEL TANK PRESSURE SENSOR - HYBRID VEHICLE CONTROL ECU)
A -- Continue to next step.
2. CHECK HARNESS AND CONNECTOR (FUEL TANK PRESSURE SENSOR - HYBRID VEHICLE CONTROL ECU)





(a) Turn the power switch off.
(b) Disconnect the hybrid vehicle control ECU connector.
(c) Measure the resistance between the PTNK terminal of the hybrid vehicle control ECU connector and body ground.
Result:





(d) Reconnect the hybrid vehicle control ECU connector.
B -- REPLACE HYBRID VEHICLE CONTROL ECU
A -- Continue to next step.
3. CHECK HARNESS AND CONNECTOR (FUEL TANK PRESSURE SENSOR - HYBRID VEHICLE CONTROL ECU)





(a) Remove the fuel tank assembly.
(b) Disconnect the fuel tank pressure sensor connector.
(c) Disconnect the hybrid vehicle control ECU connector.
(d) Measure the resistance between the PTNK terminal of the hybrid vehicle control ECU connector and body ground.
Result:





(e) Reconnect the pressure sensor connector.
(f) Reconnect the hybrid vehicle control ECU connector.
B -- REPAIR OR REPLACE HARNESS OR CONNECTOR
A -- REPLACE FUEL TANK PRESSURE SENSOR
4. CHECK HARNESS AND CONNECTOR (FUEL TANK PRESSURE SENSOR - HYBRID VEHICLE CONTROL ECU)





(a) Remove the fuel tank assembly.
(b) Disconnect the fuel tank pressure sensor connector.
(c) Turn the power switch on (IG).
(d) Measure the voltage and resistance according to the value(s) in the table below.
Standard:






Result:





(e) Reconnect the canister connector.
B -- REPAIR OR REPLACE HARNESS OR CONNECTOR
A -- Continue to next step.
5. REPLACE FUEL TANK PRESSURE SENSOR
(a) Replace the fuel tank pressure sensor Components.
NEXT -- CHECK WHETHER DTC OUTPUT RECURS (AFTER REPAIR)
6. REPAIR OR REPLACE HARNESS OR CONNECTOR
HINT: If the exhaust tail pipe has been removed, go to the next step before reinstalling it.

NEXT -- CHECK WHETHER DTC OUTPUT RECURS (AFTER REPAIR)
7. REPLACE HYBRID VEHICLE CONTROL ECU
(a) Replace the hybrid vehicle control ECU Components.
NEXT -- CHECK WHETHER DTC OUTPUT RECURS (AFTER REPAIR)
8. CHECK WHETHER DTC OUTPUT RECURS (AFTER REPAIR)
(a) Connect the Techstream to the DLC3.
(b) Turn the power switch on (IG) and turn the Techstream on.
(c) Wait for at least 60 seconds.
(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
HINT: If no pending DTC is displayed on the Techstream, the repair has been successfully completed.

NEXT -- COMPLETED
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