P0121
CIRCUIT OPERATION
- A 5-volt power supply is applied on the TPS power terminal (terminal 4) from the ECM (terminal 42)
- When the throttle valve shaft is turned from the idle position to the fully opened position, the resistor between the TPS output terminal (terminal 3) and ground terminal will increase according to the rotation.
TECHNICAL DESCRIPTION
- The TPS outputs voltage which corresponds to the throttle valve opening angle.
- The ECM
DTC SET CONDITIONS
Check Conditions
- Two seconds or more have passed since the starting sequence was completed.
Judgement Criteria
- The sensor output voltage remains 2 volts or more for two seconds when engine speed is 1,000 r/min or less, and volumetric efficiency is 60% or less. or
- TPS output voltage has continued to be 0.2 volt or lower for 2 seconds.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- TPS failed or maladjusted.
- Open or shorted TPS circuit, or loose connector.
- ECM failed.
DIAGNOSIS
Required Special Tools
MB991502: Scan Tool(MUT-II)
STEP 1. Using scan tool MB991502, check data list item 14: Throttle Position Sensor.
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK"(OFF) position before connecting or disconnecting scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Set scan tool MB991502 to the data reading mode for item 14, Throttle Position Sensor.
- With the throttle valve in the idle position, voltage should be between 0.535 and 0.735 volts.
- With the throttle valve in the full-open position, voltage should be between 4.5 and 5.5 volts.
4. Turn the ignition switch to the "LOCK"(OFF) position.
Q: Is the sensor operating properly?
YES: It can be assumed that this malfunction is intermittent.
Refer to How to Use Troubleshooting/Inspection Service Points.
NO: Go to Step 2.
STEP 2. Check connector B-07 at throttle position sensor for damage.
Q: Is the connector in good condition?
YES: Go to Step 3.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 14.
STEP 3. Check the sensor supply voltage at throttle position sensor harness side connector B-07.
1. Disconnect the connector B-07 and measure at the harness side
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 4 and ground.
- Voltage should be between 4.8 and 5.2 volts.
4. Turn the ignition switch to the "LOCK"(OFF) position.
Q: Is the voltage normal?
YES: Go to Step 6.
NO: Go to Step 4.
STEP 4. Check connector C-118 at ECM
Q: Is the connector in good condition?
YES: Go to Step 5.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 14.
STEP 5. Check for open circuit and short circuit to ground between throttle position sensor connector B-07 terminal 4 and ECM connector C-118 terminal 42
Q: Is the harness wire in good condition?
YES: Replace the ECM or PCM. Then go to Step 14.
NO: Repair it. Then go to Step 14.
STEP 6. Check the continuity at throttle position sensor harness side connector B-07.
1. Disconnect the connector B-07 and measure at the harness side.
2. Measure the continuity between terminal 1 and ground. Should be less than 2 Ohms.
Q: Is the continuity normal?
YES: Go to Step 9.
NO: Go to Step 7.
STEP 7. Check connector C-118 at ECM
Q: Is the connector in good condition?
YES: Go to Step 8.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 14.
STEP 8. Check for open circuit and harness damage between throttle position sensor connector B-07 terminal 1 and ECM connector C-118 terminal 49
Q: Is the harness wire in good condition?
YES: Replace the ECM or PCM. Then go to Step 14.
NO: Repair it. Then go to Step 14.
STEP 9. Check the throttle position sensor.
1. Disconnect the connector B-07.
2. Measure the resistance between throttle position sensor side connector terminal 1 and 4.
Standard value: 3.5 - 6.5 kOhms
3. Measure resistance between the throttle position sensor side connector terminal 1 and 3.
4. Move the throttle valve from the idle position to the full-open position.
- Resistance should change smoothly in proportion to the opening angle of the throttle valve.
Q: Is the resistance normal?
YES: Go to Step 10.
NO: Replace the throttle position sensor. Then go to Step 14.
STEP 10. Check connector C-118, C-122 at ECM
Q: Is the connector in good condition?
YES: Go to Step 11.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 14.
STEP 11. Check for open circuit and short circuit to ground between throttle position sensor connector B-07 terminal 3 and ECM connector C-122 terminal 78
Q: Is the harness wire in good condition?
YES: Go to Step 12.
NO: Repair it. Then go to Step 14.
STEP 12. Check for short circuit to ground between throttle position sensor connector and auto-cruise control ECU.
Refer to Auto Cruise Control System - Diagnostic Trouble Code Chart.
Q: Is the harness wire in good condition?
YES: Go to Step 13.
NO: Repair it. Then go to Step 14.
STEP 13. Using scan tool MB991502, check data list item 14: Throttle Position Sensor.
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK"(OFF) position before connecting or disconnecting scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Set scan tool MB991502 to the data reading mode for item 14, Throttle Position Sensor.
- With the throttle valve in the idle position, voltage should be between 0.535 and 0.735 volts.
- With the throttle valve in the full-open position, voltage should be between 4.5 and 5.5 volts.
4. Turn the ignition switch to the "LOCK"(OFF) position.
Q: Is the sensor operating properly?
YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points.
NO: Replace the ECM or PCM. Then go to Step 14.
STEP 14. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Procedure 6 - Other Monitor.
2. Check the diagnostic trouble code(DTC).
Q: Is the DTC P0121 is output?
YES: Retry the troubleshooting.
NO: The inspection is complete.