Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual: Low Pressure Fuel System Pressure - Too Low (P008A00)

DESCRIPTION

In order to supply the optimal fuel pressure according to the driving conditions and usage environment, the variable fuel system sends a drive signal from the ECM to the fuel pump control ECU assembly, steplessly performing variable control of the fuel pump (for low pressure side) and receiving feedback about the fuel pressure (for low pressure side) from the fuel pressure sensor (for low pressure side).

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	MIL	Memory	Note
P008A00	Low Pressure Fuel System Pressure - Too Low	Actual fuel pressure (for low pressure side) value less than target fuel pressure (for low pressure side) by threshold or more (1 trip detection logic).	Leak of fuel Fuel pump control ECU assembly Fuel pressure sensor (for low pressure side) Fuel pump (for low pressure side) Fuel main valve assembly (for high pressure) ECM	Does not come on	DTC stored	SAE Code: P008A

MONITOR DESCRIPTION

If the fuel pressure (for low pressure side) decreases despite an increase request signal being sent to the fuel pump control ECU assembly by the ECM, the ECM will store this DTC.

MONITOR STRATEGY

Frequency of Operation

Continuous

CONFIRMATION DRIVING PATTERN

CAUTION / NOTICE / HINT

HINT:

Read freeze frame data using the Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE

1.	CHECK FUEL LEAK

(a) Check around and beneath the vehicle for fuel leaks, fumes, etc.

OK:

No fuel leaks present.

NG

REPAIR OR REPLACE FUEL LEAK POINT

OK

2.	CHECK OTHER DTCS OUTPUT (IN ADDITION TO DTC P008A00)

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine / Trouble Codes.

(e) Read the DTCs.

Powertrain > Engine > Trouble Codes

Result	Proceed to
DTC P008A00 is output	A
DTC P008A00 and other DTCs are output	B

HINT:

If any DTCs other than P008A00 are output, troubleshoot those DTCs first.

B

GO TO DTC CHART

A

3.	PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE FUEL PUMP DUTY RATIO)

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine / Active Test / Control the Fuel Pump Duty Ratio.

Powertrain > Engine > Active Test

Tester Display
Control the Fuel Pump Duty Ratio

(e) Check whether the fuel pump operating sound occurs when performing the Active Test on the Techstream.

Standard:

Techstream Operation	Standard
High	Operating sounds can be heard from fuel pump (for low pressure side)

NG

GO TO FUEL PUMP CONTROL CIRCUIT

OK

4.	PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE FUEL PUMP DUTY RATIO)

(a) Discharge the fuel pressure.

HINT:

DTCs may be stored during this inspection. Check for DTCs and clear them using the Techstream.

(1) Remove the FUEL PMP fuse from the engine room relay block and junction block assembly.

(2) Start the engine.

(3) After the engine has stopped on its own, turn the engine switch off.

(4) Crank the engine again and make sure that the engine does not start.

(5) Install the FUEL PMP fuse.

(b) Connect the Techstream to the DLC3.

(c) Turn the engine switch on (IG).

(d) Turn the Techstream on.

(e) Enter the following menus: Powertrain / Engine / Active Test / Control the Fuel Pump Duty Ratio / Data List / Fuel Pressure (Low) / Fuel Pressure 2.

Powertrain > Engine > Active Test

Active Test Display
Control the Fuel Pump Duty Ratio

Data List Display
Fuel Pressure (Low) / Fuel Pressure 2

(f) Read the value displayed on the Techstream when the Active Test was performed.

Standard:

Techstream Operation	Standard
Low to High	When switching from Low to High, Fuel Pressure (Low) / Fuel Pressure 2 value changes

HINT:

Once the fuel pressure becomes high, the fuel pressure will not decrease, even when switched from High to Low. Therefore, make sure that the fuel pressure is low before checking that the fuel pressure changes when switching from Low to High.

NG

GO TO STEP 9

OK

5.	PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE FUEL PUMP DUTY RATIO)

(a) Discharge the fuel pressure.

HINT:

DTCs may be stored during this inspection. Check for DTCs and clear them using the Techstream.

(1) Remove the FUEL PMP fuse from the engine room relay block and junction block assembly.

(2) Start the engine.

(3) After the engine has stopped on its own, turn the engine switch off.

(4) Crank the engine again and make sure that the engine does not start.

(5) Install the FUEL PMP fuse.

(b) Connect the Techstream to the DLC3.

(c) Turn the engine switch on (IG).

(d) Turn the Techstream on.

(e) Enter the following menus: Powertrain / Engine / Active Test / Control the Fuel Pump Duty Ratio / Data List / Fuel Pressure (Low) / Fuel Pressure 2.

Powertrain > Engine > Active Test

Active Test Display
Control the Fuel Pump Duty Ratio

Data List Display
Fuel Pressure (Low) / Fuel Pressure 2

(f) Read the value displayed on the Techstream when the Active Test was performed.

Standard:

Techstream Operation	Fuel Pressure (Low) / Fuel Pressure 2
Low	50 kPag or higher
High	420 kPag or higher

HINT:

Once the fuel pressure becomes high, the fuel pressure will not decrease, even when switched from High to Low. Therefore, make sure that the fuel pressure is low before checking that the fuel pressure changes when switching from Low to High.

OK:

Actual Low and High values are as shown above.

NG

GO TO STEP 8

OK

6.	PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE FUEL PUMP DUTY RATIO)

(a) Install the fuel pressure gauge (for low pressure line of low pressure side).

Click here

(b) Connect the Techstream to the DLC3.

(c) Turn the engine switch on (IG).

(d) Turn the Techstream on.

(e) Enter the following menus: Powertrain / Engine / Active Test / Control the Fuel Pump Duty Ratio / Data List / Fuel Pressure (Low) / Fuel Pressure 2.

Powertrain > Engine > Active Test

Active Test Display
Control the Fuel Pump Duty Ratio

Data List Display
Fuel Pressure (Low) / Fuel Pressure 2

(f) Compare the values in the Data List using the Techstream and the fuel pressure gauge when the Active Test was performed.

Standard:

Techstream Operation	Result
Low	Data List value and fuel pressure gauge are within +/-50 kPa of each other
High

HINT:

Perform "Inspection After Repair" after replacing the fuel pressure sensor (for low pressure side).

Click here

NG

REPLACE FUEL DELIVERY PIPE SUB-ASSEMBLY (FUEL PRESSURE SENSOR (FOR LOW PRESSURE SIDE))

OK

7.	CHECK WHETHER DTC OUTPUT RECURS (DTC P008A00)

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Clear the DTCs.

Powertrain > Engine > Clear DTCs

(e) Turn the engine switch off and wait for at least 30 seconds.

(f) Start the engine and warm it up.

(g) Turn the Techstream on.

(h) Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.

(i) Enter the following menus: Powertrain / Engine / Utility / All Readiness.

Powertrain > Engine > Utility

Tester Display
All Readiness

(j) Input the DTC: P008A00.

(k) Check the DTC judgment result.

Result	Proceed to
NORMAL (DTCs are not output)	A
ABNORMAL (DTC P008A00 is output)	B

A

CHECK FOR INTERMITTENT PROBLEMS

B

REPLACE ECM

8.	READ VALUE USING TECHSTREAM (FUEL PRESSURE (LOW) / FUEL PRESSURE 2)

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Start the engine.

(e) Enter the following menus: Powertrain / Engine / Data List / Fuel Pressure (Low) / Fuel Pressure 2.

Powertrain > Engine > Data List

Tester Display
Fuel Pressure (Low) / Fuel Pressure 2

(f) Record the Fuel Pressure (Low) / Fuel Pressure 2 value.

(g) Turn the engine switch off.

(h) Wait for 10 seconds.

(i) Turn the engine switch on (IG).

(j) Turn the Techstream on.

(k) Enter the following menus: Powertrain / Engine / Data List / Fuel Pressure (Low) / Fuel Pressure 2.

Powertrain > Engine > Data List

Tester Display
Fuel Pressure (Low) / Fuel Pressure 2

(l) Compare the Fuel Pressure (Low) / Fuel Pressure 2 value recorded with the engine running to the Fuel Pressure (Low) / Fuel Pressure 2 value currently shown on the Techstream.

Result	Proceed to
Fuel Pressure (Low) / Fuel Pressure 2 value is maintained	A
Fuel Pressure (Low) / Fuel Pressure 2 value drops	B

HINT:

Perform "Inspection After Repair" after replacing the fuel pump (for low pressure side).

Click here

A

REPLACE FUEL PUMP (FOR LOW PRESSURE SIDE)

B

REPLACE FUEL MAIN VALVE ASSEMBLY (FOR HIGH PRESSURE)

9.	PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE FUEL PUMP DUTY RATIO)

(a) Install the fuel pressure gauge (for low pressure line of low pressure side).

Click here

(b) Connect the Techstream to the DLC3.

(c) Turn the engine switch on (IG).

(d) Turn the Techstream on.

(e) Enter the following menus: Powertrain / Engine / Active Test / Control the Fuel Pump Duty Ratio / Data List / Fuel Pressure (Low) / Fuel Pressure 2.

Powertrain > Engine > Active Test

Active Test Display
Control the Fuel Pump Duty Ratio

Data List Display
Fuel Pressure (Low) / Fuel Pressure 2

(f) Read the values in the Data List using the Techstream and the fuel pressure gauge when the Active Test was performed.

Techstream Operation	Result	Proceed to
Low to High	Data List value does not change, but fuel pressure gauge changes	A
	Data List value and fuel pressure gauge do not change	B

HINT:

Perform "Inspection After Repair" after replacing the fuel pressure sensor (for low pressure side).

Click here

A

REPLACE FUEL DELIVERY PIPE SUB-ASSEMBLY (FUEL PRESSURE SENSOR (FOR LOW PRESSURE SIDE))

B

REPLACE FUEL PUMP CONTROL ECU ASSEMBLY