Dtc P1251 Turbocharger / Supercharger Overboost Condition (Too High)

DESCRIPTION

WIRING DIAGRAM

INSPECTION PROCEDURE

CHECK FOR ANY OTHER DTCS OUTPUT (RECORD STORED DTC AND FREEZE FRAME DATA)

CHECK AIR INTAKE SYSTEM

REPAIR OR REPLACE AIR INTAKE SYSTEM

CHECK TURBOCHARGER SUB-ASSEMBLY (DC MOTOR OPERATION)

PERFORM ACTIVE TEST USING INTELLIGENT TESTER (ACTIVATE THE EGR VALVE CLOSE)

CHECK ELECTRIC EGR CONTROL VALVE ASSEMBLY (CHECK VACUUM)

REMOVE DEPOSIT (ELECTRIC EGR CONTROL VALVE ASSEMBLY)

REPAIR OR REPLACE VACUUM HOSE

READ VALUE USING INTELLIGENT TESTER (INJECTION VOLUME)

REPLACE INJECTOR ASSEMBLIES OF ALL CYLINDERS

BLEED AIR FROM FUEL SYSTEM

REGISTER INJECTOR COMPENSATION CODE AND PERFORM PILOT QUANTITY LEARNING

CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED

CHECK HARNESS AND CONNECTOR (TURBO MOTOR DRIVER - TURBOCHARGER SUB-ASSEMBLY)

DESCRIPTION

HINT:

Refer to DTC P0046 (Toyota Fortuner RM000002NCM00TX_06.html).

HINT:

*: The threshold value changes depending on the engine speed.

HINT:

If DTC P1251 is stored due to the VN turbo vane being stuck closed, the following symptoms may appear:

1. Vehicle surge when driving with full load
   
2. Sudden lack of power due to power being limited
   

WIRING DIAGRAM

1. Refer to DTC P0046 (Toyota Fortuner RM000002NCM00TX_07.html).
   
2. Refer to DTC P2563 (Toyota Fortuner RM000002PPN01HX_02.html).
   

INSPECTION PROCEDURE

NOTICE:

After replacing the ECM, the new ECM needs registration (Toyota Fortuner RM0000012XK030X.html) and initialization (Toyota Fortuner RM0000012X2005X.html).

HINT:

Read freeze frame data using the intelligent tester. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, and other data from the time the malfunction occurred.

1. Connect the intelligent tester to the DLC3.
   

2. Turn the ignition switch to ON and turn the tester on.
   

3. Enter the following menus: Powertrain / Engine and ECT / DTC.
   

4. Read the DTCs.
   

   HINT:

   1. Record the stored DTC and Freeze Frame Data.
      
   2. Be sure to carefully examine "MAP" and "Target Booster Pressure" in the freeze frame data.
      

   Result

   Result	Proceed to
   P1251 is output	A
   P1251 and other DTCs are output	B

   HINT:

   DC motor-related DTCs: P0046 (Toyota Fortuner RM000002NCM00TX.html), P0047 and P0048 (Toyota Fortuner RM000002PPL01YX.html).

   Nozzle vane position sensor-related DTCs: P2563, P2564, P2565, P2588 and P2589 (Toyota Fortuner RM000002PPN01HX.html).

1. Check if the hoses between the air cleaner and turbocharger, and turbocharger and intake manifold are damaged or disconnected.
   

   Result

   Result	Proceed to
   Hoses or pipes are damaged or disconnected	A
   No hoses or pipes are damaged or disconnected	B

   HINT:

   1. Be sure to check if the hoses and pipes between the air cleaner and compressor are disconnected as disconnection of a hose or pipe can cause overboost. Also, check the high pressure hoses for disconnection due to overboost.
      
   2. Check for disconnection of the exhaust pipes.
      
   3. Using your hand, check whether the pipes and hoses in the intake system are securely connected.
      
   4. Check for any modifications in the intake system made by the user.
      

1. Repair or replace the malfunctioning part in the air intake system.
   

1. Check the turbocharger sub-assembly (Toyota Fortuner RM00000143S002X.html).
   

   HINT:

   Check the movement of the actuator rod when the ignition switch is turned from ON to off.

1. Connect the intelligent tester to the DLC3.
   

2. Start the engine and warm it up, and make sure the A/C switch and all accessory switches are off.
   

3. Turn the ignition switch off. Wait for 30 seconds, and then restart the engine.
   

4. Turn the tester on.
   

5. Enter the following menus: Powertrain / Engine and ECT / Data List / MAF.
   

6. Read the MAF value displayed on the tester while the engine is idling.
   

7. Enter the following menus: Powertrain / Engine and ECT / Active Test / Activate the EGR Valve Close.
   

8. Read the MAF value when the EGR valve is closed using the Active Test function.
   

   HINT:

   1. If idling continues for 15 minutes or more, the EGR valve target opening angle becomes 0% (EGR valve fully closed). As this makes diagnosis impossible, it becomes necessary to drive the vehicle or to restart the engine.
      
   2. Before performing the diagnosis, confirm that the EGR valve target opening angle is not 0%.
      

   Result

   Active Test	Result	Proceed to
   Activate the EGR Valve Close: Off (Open) to On (Closed)	MAF value does not change	A
   	MAF value changes	B

   NOTICE:

   As the measured values may differ from those shown below due to factors such as differences in measuring environments and changes in vehicle condition due to aging, do not use these values to determine whether the vehicle is malfunctioning or not.

   HINT:

   The problem may be a temporary one, due to the entry of deposits or foreign matter. Check that there are no deposits or foreign matter in the electric vacuum regulating valve assembly or mass air flow meter.

   Reference:

   EGR Valve Condition (Opening)	Measuring Condition	MAF (Reference)
   Open (55%)	Atmosphere pressure: 101 kPa Intake air temperature: 30°C (86°F) Engine coolant temperature: 88°C (190°F)	3.0 to 9.0 gm/s
   Closed (0%)		15 to 22 gm/s

1. Disconnect the vacuum hose from the electric EGR control valve assembly.
   

2. Start the engine.
   

3. Check if there is suction from the vacuum hose during idling.
   

   HINT:

   If idling continues for 15 minutes or more, the EGR valve target opening angle becomes 0% (EGR valve fully closed). As this makes diagnosis impossible, it becomes necessary to drive the vehicle or to restart the engine.

   OK:

   Suction exists.
   

1. Remove the electric EGR control valve assembly (Toyota Fortuner RM00000141A004X.html).
   

2. Visually check the electric EGR control valve assembly for deposits. If there are deposits, clean the electric EGR control valve assembly.
   

   HINT:

   1. If the EGR valve is stuck closed, the intake air amount increases and engine vibration may worsen.
      
   2. If the EGR valve does not operate due to clogging or disconnection of the vacuum hose, repair the hose.
      
   3. If the EGR valve does not close properly or is stuck open, EGR becomes excessive and combustion becomes unstable. Also, there may be a lack of power.
      

3. Reinstall the electric EGR control valve assembly (Toyota Fortuner RM000001417004X.html).
   

1. Repair or replace of the EGR valve system vacuum hose.
   

1. Connect the intelligent tester to the DLC3.
   

2. Start the engine and warm it up until the engine coolant temperature reaches 70°C (158°F) or higher.
   

3. Allow the engine to idle for 1 minute or more.
   

   HINT:

   The A/C switch and all accessory switches should be off with a fully warm engine.

4. Turn the tester on.
   

5. Enter the following menus: Powertrain / Engine and ECT / Data List / Injection Volume.
   

6. Read the values during engine idling.
   
   

   Result

   Result	Proceed to
   Injection Volume is less than 5 mm3/st	A
   Except above	B

   HINT:

   1. If the injector assembly is malfunctioning, the compensatory injection volume remains at 5.0 mm³/st.
      
   2. If there is a disconnection, the feedback value will increase and +5.0 mm³/st will be indicated, because it will become impossible for the injector to inject.
      

1. Replace the injector assemblies (Toyota Fortuner RM000002SY100QX.html).
   

1. Bleed the air from the fuel system (Toyota Fortuner RM0000014FK006X_01_0002.html).
   

1. Register the injector compensation code (Toyota Fortuner RM0000012XK030X_02_0003.html).
   

2. Perform the injector pilot quantity learning (Toyota Fortuner RM0000012XK030X_02_0009.html).
   

1. Connect the intelligent tester to the DLC3.
   

2. Clear the DTCs (Toyota Fortuner RM0000012WY00LX.html).
   

3. Turn the ignition switch off.
   

4. Start the engine and warm it up.
   

5. Confirm the value of Engine Speed from the Freeze Frame Data recorded previously, and then drive the vehicle according to the Engine Speed value.
   

   HINT:

   Take a snapshot of MAP and Target Boost Pressure in the Data List with the intelligent tester while driving the vehicle.

6. Read the DTCs.
   
   

   Result

   Result	Proceed to
   P1251 is not output and the amount by which MAP exceeds Target Boost Pressure is 20 kPa or less	A
   Except above	B*

   HINT:

   *: Return to "Check Air Intake System" and inspect areas that have not been inspected yet.

1. Disconnect the T10 DC motor connector.
   

2. Disconnect the T11 nozzle vane position sensor connector.
   

3. Disconnect the T34 turbo motor driver connector.
   

4. Measure the resistance according to the value(s) in the table below.
   

   Standard Resistance (Check for Open):

   Tester Connection	Condition	Specified Condition
   M+ (T10-2) - M+ (T34-12)	Always	Below 1 Ω
   M- (T10-1) - M- (T34-5)	Always	Below 1 Ω
   VTA1 (T11-1) - VTA1 (T34-9)	Always	Below 1 Ω
   VNE2 (T11-2) - VNE2 (T34-8)	Always	Below 1 Ω
   VNVC (T11-3) - VNVC (T34-1)	Always	Below 1 Ω
   VTA2 (T11-4) - VTA2 (T34-10)	Always	Below 1 Ω
   E2S (T11-5) - E2S (T34-11)	Always	Below 1 Ω
   VCS (T11-6) - VCS (T34-6)	Always	Below 1 Ω

   Standard Resistance (Check for Short):

   Tester Connection	Condition	Specified Condition
   M+ (T10-2) or M+ (T34-12) - Body ground	Always	10 kΩ or higher
   M- (T10-1) or M- (T34-5) - Body ground	Always	10 kΩ or higher
   VTA1 (T11-1) or VTA1 (T34-9) - Body ground	Always	10 kΩ or higher
   VNE2 (T11-2) or VNE2 (T34-8) - Body ground	Always	10 kΩ or higher
   VNVC (T11-3) or VNVC (T34-1) - Body ground	Always	10 kΩ or higher
   VTA2 (T11-4) or VTA2 (T34-10) - Body ground	Always	10 kΩ or higher
   E2S (T11-5) or E2S (T34-11) - Body ground	Always	10 kΩ or higher
   VCS (T11-6) or VCS (T34-6) - Body ground	Always	10 kΩ or higher

5. Reconnect the T10 DC motor connector.
   

6. Reconnect the T11 nozzle vane position sensor connector.
   

7. Reconnect the T34 turbo motor driver connector.