Troubleshooting

DTC P0120 THROTTLE/PEDAL POSITION SENSOR/SWITCH "A" CIRCUIT MALFUNCTION


CIRCUIT DESCRIPTION

DTC Detecting condition:

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 V is applied to terminal VTA1 of the ECM. The voltage applied to terminals VTA1 of the ECM increases in proportion to the opening angle of the throttle valve and becomes approximately 2.7 - 5.2 V when the throttle valve is fully opened. The ECM judges the vehicle driving conditions by these signals output from terminals VTA1 and uses them as one of the conditions for deciding the air-fuel ratio correction, power increase correction and fuel-cut control etc.






HINT: After confirming DTC P0120, use the OBD II scan tool or LEXUS hand-held tester to confirm the throttle valve opening percentage and closed throttle position switch condition.

Wiring Diagram:

Steps 1 - 2:

Steps 3 - 4:

Step 5:

INSPECTION PROCEDURE

HINT: If DTCs P0110, P0115 and P0120 are output simultaneously, E2 (sensor ground) bay be open. Read freeze frame data using LEXUS hand-held tester or OBD II scan tool, as freeze frame data 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 was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.

CHECK FOR INTERMITTENT PROBLEMS

HINT:
LEXUS hand-held tester only:
By putting the vehicle's ECM in the check mode, 1 trip detection logic is possible instead of 2 trip detection logic and the sensitivity to detect open circuits is increased. This makes it easier to detect intermittent problems.

a. Clear the DTC (See step 2).
b. Set the check mode (See step 3).
c. Perform a simulation test.
d. Check the connector and terminal.
e. Handle the connector.