Troubleshooting

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

HINT: This is the purpose of the "throttle position sensor".

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 0.3 to 0.8 V is applied to terminal VTA of the ECM. The voltage applied to the terminals VTA of the ECM increases in proportion to the opening angle of the throttle valve and becomes approximately 3.2 to 4.9 V when the throttle valve is fully opened. The ECM judges the vehicle driving conditions from this signal input from terminal VTA, and uses it 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, confirm the throttle valve opening percentage and closed throttle position switch condition using the hand-held tester or the OBD II scan tool.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

Component Operating Range:

The throttle position sensor varies its resistance with the angle of the throttle valve. The ECM applies a regulated reference voltage to the throttle position sensor positive terminal and calculates the angle of the throttle valve based on the current voltage at the throttle position sensor "signal" terminal. When the throttle valve is near the fully closed position, the output voltage of the throttle position sensor is low. When it is near the fully open position, the output voltage is high. If the ECM detects that the output voltage of the throttle position sensor is out of the normal range, the ECM interprets this as a malfunction in the throttle position sensor and sets a DTC.

Wiring Diagram:

INSPECTION PROCEDURE

Step 1 - 2:

Step 3 - 4:

Step 5:

Hand-held tester

Step 1 - 2:

OBD II scan tool (excluding hand-held tester)

HINT:
- If different DTCs related to different systems that have terminal E2 as the ground terminal are output simultaneously, terminal E2 may be open.
- Read freeze frame data using the hand-held tester or the OBD II scan tool. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, as well as other data from the time when a malfunction occurred.

CHECK FOR INTERMITTENT PROBLEMS

Hand held tester only:
Inspect the vehicle's ECM using check mode. Intermittent problems are easier to detect when the ECM is in check mode with hand held tester. In check mode, the ECM uses 1 trip detection logic, which has a higher sensitivity to malfunctions than normal mode (default), which uses 2 trip detection logic.
a. Clear the DTCs. (See step 2)
b. Set the check mode. (See step 3)
c. Perform a simulation test.
d. Check the connector and terminal.
e. Wiggle the harness and connector.