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P0120

Throttle Position Sensor (TPS) Circuit:






CIRCUIT OPERATION
- A 5-volt power supply is applied on the TPS power terminal (terminal 4) from the PCM (terminal 46).
The ground terminal (terminal 4) is grounded with PCM (terminal 57).
- 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 PCM checks whether the voltage is within a specified range. In addition, it checks that the voltage output does not become too large while the engine is at idle.

DTC SET CONDITIONS

Check Condition
- 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.

Check Condition
- Two seconds or more have passed since the staring sequence was completed.
- Engine speed is lower than 3,000 r/min.
- Volumetric efficiency is lower than 30 percent.

Judgement Criteria
- TPS output voltage has continued to be 4.6 volts or higher for 2 seconds.

Check Condition
- Two seconds or more have passed since the staring sequence was completed.
- Engine speed is higher than 2,000 r/min.
- Volumetric efficiency is higher than 60 percent.

Judgement Criteria
- TPS output voltage has continued to be 0.8 volt or lower for 2 seconds.

TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- TPS failed or misadjusted.
- Open or shorted TPS circuit, or loose connector.
- PCM failed.

DIAGNOSIS
Required Special Tool:
MB991502: Scan Tool (MUT-II)

CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.




STEP 1. Using scan tool MB991502, check data list item 14: Throttle Position Sensor.
1. Connect scan tool MB991502 to the data link connector.
2. Turn the ignition switch to "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 volt.
- 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 "LOCK" (OFF) position.

If not within specifications, go to Step 2.

If within specifications, this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction.




STEP 2. Check the throttle position sensor (TPS).
1. Disconnect the TPS connector B-05.




2. Measure the resistance between the TPS side connector terminals 1 and 4.

Standard value: 3.5 - 6.5 kOhms




3. Measure the resistor between the TPS side connector terminals 1 and 3. With test probes in place, 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.

If all checks above meet the specifications, go to Step 3.

If any check above does not meet the specifications, replace the TPS. Refer to Throttle Body - Disassembly and Assembly. Then go to Step 8.




STEP 3. Check the circuits at the throttle position sensor (TPS) connector B-05.
1. Disconnect connector B-05 and measure at the harness side.
2. Turn the ignition switch to "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 "LOCK" (OFF) position.
5. Check for the continuity between terminal 1 and ground.
- Should be less than 2 Ohms.

If all checks above meet the specifications, go to Step 4.

If any check above does not meet the specifications, go to Step 6.




STEP 4. Check harness connector B-05 at the TPS for damage.
If harness connector B-05 is in good condition, go to Step 5.

If harness connector B-05 is damaged, repair or replace it.

Refer to Harness Connector Inspection.

Then go to Step 7.




STEP 5. Check harness connectors C40, C41 at the PCM for damage.
If harness connectors C-40, C-41 are damaged, repair or replace it. Refer to Harness Connector Inspection. Then go to Step 7.

If harness connectors C-40, C-41 are in good condition, go to Step 6.







STEP 6. Check the harness wire between throttle position sensor (TPS) connector B-05 and PCM connectors C40, C41.
If the wire between TPS connector B-05 and PCM connectors C-40, C-41 are not damaged, replace the PCM. Then go to Step 7.

If the wire between TPS connector B-05 and PCM connectors C-40, C-41 are damaged, repair it. Then go to Step 7.

STEP 7. Test the OBD-II drive cycle
1. Carry out a test drive with the drive cycle pattern. Procedure 6 - Other Monitor.
2. Read the diagnostic trouble code, and confirm that diagnostic trouble code P0120 dose not reset.
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