My 1999 Lexus Es300 had 8 codes. 2 old ( both knock sensors, both have been replaced along with the wiring harness). Yesterday car started to smell faintly of gas fumes. Today car was running fine , then at stoplight it started to idle rough and stumble. And 6 new codes along with it. P0120, P0441 (shows this code twice), P0300, P0304 and P0305
The 3 p0300 codes are all misfire codes. P0300 is a multiple misfire code and P0304 is cylinder # 4 and P0305 is cylinder #5. Could be a blown head gasket or a glitch if it continues after trying to reset codes and test. As for the other codes I have outlined there meaning below. The P0441 will not effect drivability so I would concentrate on the other codes first.
Code P0120 – Throttle/Pedal position sensor/switch “A” circuit malfunction
Code P0120 Description
The throttle position sensor is mounted in the throttle body and detects the throttle valve opening angle. When the throttle valve is fully closed, a voltage of approximately 0.7 is applied to terminal VTA and the ECM. This voltage increases in proportion to the opening angle of the throttle valves and becomes approximately 2.7 ~ 5.2V when throttle is fully open. The ECM judges the vehicle driving conditions from these signals input from terminals VTA and uses them as one of the conditions for deciding the air-fuel-ratio correction, power increase correction and fuel-cut control etc.
Inspection Procedure
HINT: If DTCs P0110 (Intake Air Temp. Circuit Malfunction) and P0115 (Engine Coolant Temp. Circuit Malfunction) and P0120 (Throttle/Pedal Position Sensor/Switch ”A” Circuit Malfunction) are output simultaneously, E2 (sensor ground) bay be open. Read freeze frame data using LEXUS hand-held tester or OBD II scan tool. Because freeze frame records the engine conditions when the malfunction is detected, when troubleshooting it is useful for determining whether the vehicle was running or stopped, the engine warmed up or not, the air-fuel ratio lean or rich, etc. at the time of the malfunction.
Code P0120 Possible Causes
- Open or short in throttle position sensor circuit
- Throttle Position Sensor
- ECM
Throttle Position Wiring Diagram
Code P0441 – Evaporative Emission Control System Incorrect Purge Flow
Code P0441 Description
The vapor pressure sensor and VSV for vapor pressure sensor are used to detect abnormalities in the evaporative emission control system. The ECM decides whether there is an abnormality in the evaporative emission control system based on the vapor pressure sensor signal. DTCs P0441 and P0446 are recorded by the ECM when evaporative emissions leak from the components within the dotted line in fig. 1 below, or when there is a malfunction in either the VSV for EVAP, the VSV for vapor pressure sensor, or in the vapor pressure sensor itself.
