Dtc P0234 Turbocharger / Supercharger Overboost Condition
Lexus IS250 IS220d GSE20 ALE20 2AD-FHV ENGINE CONTROL SYSTEM
DESCRIPTION
WIRING DIAGRAM
INSPECTION PROCEDURE
CHECK OTHER DTC OUTPUT (IN ADDITION TO DTC P0234, P0299 AND/OR P1251)
CHECK CONNECTION OF VACUUM HOSES
CHECK VACUUM (TURBOCHARGER - E-VRV FOR TURBOCHARGER CONTROL)
CHECK TERMINAL VOLTAGE (E-VRV POWER SOURCE)
CHECK E-VRV FOR TURBOCHARGER CONTROL (E-VRV OPERATION)
CHECK E-VRV FOR TURBOCHARGER CONTROL (E-VRV RESISTANCE)
CHECK HARNESS AND CONNECTOR (E-VRV FOR TURBOCHARGER CONTROL - ECM)
INSPECT TURBOCHARGER SUB-ASSEMBLY
INSPECT EGR VALVE ASSEMBLY
CHECK MANIFOLD ABSOLUTE PRESSURE SENSOR
DTC P0234 Turbocharger / Supercharger Overboost Condition
DTC P0299 Turbocharger / Supercharger Underboost
DTC P1251 Turbocharger / Supercharger Overboost Condition (Too High)
DESCRIPTION
DTC No. | DTC Detection Condition | Trouble Area |
P0234 |
Turbochaging pressure is higher than the threshold for 60 seconds. (1 trip detection logic) | E-VRV for turbocharger control
Open or short in VRV circuit
Turbocharger
Vacuum hose
EGR valve
ECM
|
P0299 |
Turbochaging pressure is lower than the threshold for 40 seconds when the turbochaging pressure deviates from the requirement. (2 trip detection logic) |
P1251 |
Turbochaging pressure is higher than the requirement for 0.5 seconds. (1 trip detection logic) |
WIRING DIAGRAM

INSPECTION PROCEDURE
- After replacing the ECM, the new ECM needs registration and initialization .
1.CHECK OTHER DTC OUTPUT (IN ADDITION TO DTC P0234, P0299 AND/OR P1251) |
Connect the intelligent tester to the DLC3.
Turn the engine switch ON (IG) and turn the intelligent tester ON.
Enter the following menus: "Powertrain / Engine / DTC".
Read DTCs.
- Result:
Display (DTC output) | Proceed to |
P0234, P0299 and/or P1251 | A |
P0234, P0299 and/or P1251 and other DTCs | B |
4.CHECK TERMINAL VOLTAGE (E-VRV POWER SOURCE) |
Disconnect the E79 E-VRV connector.
Measure the voltage.
- Standard voltage:
Tester Connection | Specified Condition |
VRV (E79-1) - Body ground | 9 to 14 V |
| REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
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5.CHECK E-VRV FOR TURBOCHARGER CONTROL (E-VRV OPERATION) |
Check the E-VRV operation .
| REPLACE E-VRV FOR TURBOCHARGER CONTROL |
|
|
6.CHECK E-VRV FOR TURBOCHARGER CONTROL (E-VRV RESISTANCE) |
Measure the E-VRV resistance .
- Standard resistance:
- 11.1 to 12.5 Ω
| REPLACE E-VRV FOR TURBOCHARGER CONTROL |
|
|
7.CHECK HARNESS AND CONNECTOR (E-VRV FOR TURBOCHARGER CONTROL - ECM) |
Disconnect the E79 E-VRV connector.
Disconnect the E59 ECM connector.
Check the resistance between the wire harness side connectors.
- Standard resistance (Check for open):
Tester Connection | Specified Condition |
VN (E59-84) - VRV (E79-2) | Below 1 Ω |
- Standard resistance (Check for short):
Tester Connection | Specified Condition |
VN (E59-84) or VRV (E79-2) - Body ground | 10 kΩ or higher |
Reconnect the E-VRV connector.
Reconnect the ECM connector.
| REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
|
8.INSPECT TURBOCHARGER SUB-ASSEMBLY |
Check the turbocharging pressure .
- Standard:
- 48 to 53 kPa (0.49 to 0.54 kgf/cm2, 6.9 to 7.7 psi)
| REPLACE TURBOCHARGER SUB-ASSEMBLY |
|
|
9.INSPECT EGR VALVE ASSEMBLY |
Disconnect the E64 EGR valve connector.
Measure the resistance between the terminals of the EGR valve.
- Standard resistance:
Tester Connection | Condition | Specified Condition |
1 - 5 | 20°C (68°F) | 6.5 to 7.5 Ω |
Reconnect the EGR valve connector.
| REPLACE EGR VALVE ASSEMBLY |
|
|
10.CHECK MANIFOLD ABSOLUTE PRESSURE SENSOR |
Connect an intelligent tester to the DLC3.
Turn the engine switch ON (IG) and turn the tester on.
Select the following menu items: Powertrain / Engine and ECT / Data List / Map and Atmosphere Pressure.
Read the value displayed on the tester.
- OK:
- MAP:
- Same as atmospheric pressure.
- 1 bar of atmospheric pressure is 101 kPa.
Apply a negative pressure of 40 kPa (300 mmHg, 11.8 in.Hg) to the manifold absolute pressure sensor.
- OK:
- MAP:
- MAP decreases 40 kPa from atmospheric pressure.
Apply a positive pressure of 69 kPa (518 mmHg, 20.4 in.Hg) to the manifold absolute pressure sensor.
- OK:
- MAP:
- MAP increases 69 kPa from atmospheric pressure.
- Even if the value output from the manifold absolute sensor is within the standard level, there may be a problem with the sensor due to deterioration because of age.
| REPLACE MANIFOLD ABSOLUTE PRESSURE SENSOR |
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LEXUS IS250, IS220d / GSE20 ALE20