SFI SYSTEM (w/o Electronic Throttle Control System), Diagnostic DTC:P0122, P0123

DTC Code DTC Name
P0122 Throttle Position Sensor Circuit Low Input
P0123 Throttle Position Sensor Circuit High Input

DESCRIPTION

The throttle position sensor is mounted on the throttle body and detects the throttle valve opening angle. When the throttle valve is fully closed, a voltage of approximately 0.4 to 0.9 V is applied to terminal VTA of the ECM. The voltage applied to terminal VTA of the ECM increases in proportion to the opening angle of the throttle valve and becomes approximately 3.6 to 4.3 V when the throttle valve is fully open. The ECM monitors the vehicle driving conditions through these signals input from terminal VTA, and uses them as one of the conditions for determining the air-fuel ratio correction, power increase correction and fuel-cut control, etc.

Tech Tips

When the throttle position sensor output voltage is outside the normal range, the ECM determines this as a malfunction.

DTC No. DTC Detection Condition Trouble Area
P0122

VTA stays less than 3.14% for 0.08 seconds or more

(3 trip detection logic)

  • Throttle position sensor (built in throttle body)

  • Short in VTA circuit and E2 circuit

  • Open in VC circuit

  • ECM
P0123

VTA stays more than 95.7% for 0.08 seconds or more

(3 trip detection logic)

  • Throttle position sensor (built in throttle body)

  • Open in E2 circuit

  • VC and VTA circuit are short-circuited

  • ECM

Tech Tips


  • These DTCs are detected when the engine idles for approximately 15 seconds.

  • After confirming DTCs, confirm the throttle valve opening percentage and closed throttle position switch condition using the intelligent tester.

Throttle Valve Fully Closed Throttle Valve Fully Open Trouble Area
7 to 18 % Approximately 75 to 95 % - (Normal)
0 % 0 %

  • VC circuit open

  • VTA circuit short to GND
Approximately 100 % Approximately 100 %

  • E2 circuit open

  • VTA circuit open or +B short

FAIL-SAFE

If DTC P0122 or P0123 is detected, the ECM performs engine control using a throttle position calculated from the engine speed.

WIRING DIAGRAM

A0138JOE01

INSPECTION PROCEDURE

Tech Tips

Read freeze frame data using the intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE


  1. READ VALUE OF THROTTLE POSITION SENSOR


    1. A0137OPE08

      Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON (do not start the engine).

    3. Select the following menu items: Powertrain / Engine and ECT / Data List / Throttle POS.

    4. Read the value displayed on the intelligent tester when the accelerator pedal is operated (releasing and depressing).

      Result
      Throttle Valve Opening Position (%) Proceed To
      0 A
      Approximately 8 to 88 (Varies according to accelerator pedal opening position) B
      Approximately 100 C

    B

    GO TO "CHECK FOR INTERMITTENT PROBLEMS"

    C

    INSPECT THROTTLE POSITION SENSOR (SENSOR RESISTANCE) Click here

    A

  2. INSPECT THROTTLE POSITION SENSOR (SENSOR RESISTANCE)


    1. A013610E01

      Disconnect the B20 throttle position sensor connector.

    2. Measure the resistance between the terminals of the throttle position sensor.

      Standard resistance
      Tester Connection Specified Condition
      VC (B20-1) - E2 (B20-2) 2.5 to 5.0 kΩ
      VTA (B20-3) - E2 (B20-2) 0.3 to 6.0 kΩ

    3. Reconnect the throttle position sensor connector.


    NG

    REPLACE THROTTLE BODY ASSEMBLY

    OK

  3. CHECK HARNESS AND CONNECTOR (THROTTLE POSITION SENSOR - ECM)


    1. A0136LGE01

      Disconnect the B25 ECM connector.

    2. Disconnect the B20 throttle position sensor connector.

    3. Measure the resistance.

      Standard resistance
      Tester Connection Specified Condition
      VC (B20-1) - E2 (B20-2) 2.5 to 5.0 kΩ
      VTA (B20-3) - E2 (B20-2) 0.3 to 6.0 kΩ
      Standard resistance (check for short to GND)
      Tester Connection Specified Condition
      VC (B20-2) - Body ground 10 kΩ or higher
      VTA (B20-3) - Body ground 10 kΩ or higher

    4. Reconnect the throttle position sensor connector.

    5. Reconnect the ECM connector.


    NG

    REPAIR OR REPLACE HARNESS AND CONNECTOR

    OK

    REPLACE ECM

  4. INSPECT THROTTLE POSITION SENSOR (SENSOR RESISTANCE)


    1. A013610E01

      Disconnect the B20 throttle position sensor connector.

    2. Measure the resistance between the terminals of the throttle position sensor.

      Standard resistance
      Tester Connection Specified Condition
      VC (B20-1) - E2 (B20-2) 2.5 to 5.0 kΩ
      VTA (B20-3) - E2 (B20-2) 0.3 to 6.0 kΩ

    3. Reconnect the throttle position sensor connector.


    NG

    REPLACE THROTTLE BODY ASSEMBLY

    OK

  5. CHECK HARNESS AND CONNECTOR (THROTTLE POSITION SENSOR - ECM)


    1. A0136LGE01

      Disconnect the B25 ECM connector.

    2. Disconnect the B20 throttle position sensor connector.

    3. Measure the resistance.

      Standard resistance (check for open)
      Tester Connection Specified Condition
      VC (B20-1) - VC (B25-29) Below 1 Ω
      VTA (B20-3) - VTA (B25-80) Below 1 Ω
      E2 (B20-2) - ETA (B25-40) Below 1 Ω
      Standard resistance (check for + B short)
      Tester Connection Specified Condition
      VC (B20-1) or VC (E19-52) - VTA (B20-3) or VTA (E19-21) 10 kΩ or higher

    4. Reconnect the throttle position sensor connector.

    5. Reconnect the ECM connector.


    NG

    REPAIR OR REPLACE HARNESS AND CONNECTOR

    OK

    REPLACE ECM