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DTC P0121: Throttle Position Sensor (main) Plausibility
 
 
 
 
TECHNICAL DESCRIPTION
  • Compare the actual measurement of volumetric efficiency by a mass airflow sensor signal with the volumetric efficiency estimated from a throttle position sensor (main) signal.
  • Compare the actual measurement of manifold pressure by a manifold absolute pressure sensor signal with the manifold pressure estimated from a throttle position sensor (main) signal.
 
 
MONITOR EXECUTION
Continuous
 
 
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC set in memory for the item monitored below)
  • Not applicable
Sensor (The sensor below is determined to be normal)
  • Not applicable
 
 
DTC SET CONDITIONS
Logic Flow Chart
Check Conditions
  • The volumetric efficiency estimated by the throttle position sensor (main) subtracted from the actual volumetric efficiency is more than 0 percent. Or, the volumetric efficiency is 60 percent or less.
  • Engine speed is 750 r/min or higher.
Judgment Criterion
  • For 0.4 second, the difference between the actual volumetric efficiency and the volumetric efficiency estimated by the throttle position sensor (main) is 33 percent or more.
  • For 0.4 second, the difference between the volumetric efficiency estimated by the throttle position sensor (main) and the volumetric efficiency estimated by the throttle position sensor (sub) is 8.8 percent or more.
 
 
DTC SET CONDITIONS
Logic Flow Chart
Check Conditions
  • The manifold pressure estimated by the throttle position sensor (main) subtracted from the actual manifold pressure is more than 0 kPa (0 in.Hg). Or, the manifold pressure is 73 kPa (21.6 in.Hg) or less.
  • Engine speed is 750 r/min or higher.
Judgment Criterion
  • For 0.4 second, the difference between the actual manifold pressure and the manifold pressure estimated by the throttle position sensor (main) is 40 kPa (11.8 in.Hg) or more.
  • For 0.4 second, the difference between the manifold pressure estimated by the throttle position sensor (main) and the manifold pressure estimated by the throttle position sensor (sub) is 7 kPa (2.1 in.Hg) or more.
 
 
FAIL-SAFE AND BACKUP FUNCTION
  • Throttle opening degree is restricted.
  • Throttle opening degree position is in default position if throttle position sensor (sub) fails.
 
 
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle Pattern 7 .
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are: )
  • Throttle position sensor (main) failed.
  • Harness damage in throttle position sensor (main) circuit or loose connector contact.
  • Intake air system failed.
  • There is some foreign matter around mass airflow sensor failed.
  • Intake charge pressure control system failed.
  • ECM failed.
 
 
 
DIAGNOSIS
Required Special Tool:
  • MB991658: Test Harness
STEP 1. Using scan tool (M.U.T.-IIISE), read the diagnostic trouble code (DTC).
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-IIISE).
(1) Connect scan tool (M.U.T.-IIISE). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-IIISE) .
(2) Turn the ignition switch to the "ON" position.
(3) Read the DTC.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the diagnostic trouble code other than P0121 set?
Refer to, Diagnostic Trouble Code Chart .
Go to Step 2.
 
STEP 2. Using scan tool (M.U.T.-IIISE), check data list item 13: Throttle Position Sensor (main).
(1) Detach the intake air hose at the throttle body.
(2) Disconnect the connector of the throttle body assembly.
(3) Use test harness special tool (MB991658) to connect only terminals TPSE, TPSM, TPS5 and TPSS line.
(4) Turn the ignition switch to the "ON" position.
(5) Set scan tool (M.U.T.-IIISE) to the data reading mode for item 13, Throttle Position Sensor (main).
  • Output voltage should be between 300 and 700 millivolts when the throttle valve is fully closed with your finger.
  • Output voltage should be 4,000 millivolts or more when the throttle valve is fully open with your finger.
(6) Turn the ignition switch to the "LOCK" (OFF) position.
Is the sensor operating properly?
Go to Step 3.
Refer to, DTC P0122 - Throttle Position Sensor (main) Circuit Low Input , DTC P0123 - Throttle Position Sensor (main) Circuit High Input .
 
STEP 3. Check air intake from intake hose and intake manifold.
Are there any abnormalities?
Repair it. Then go to Step 7.
Go to Step 4.
 
STEP 4. Check for foreign matter being around the mass airflow sensor.
Are there any foreign matter?
Repair it. Then go to Step 7.
Go to Step 5.
 
STEP 5. Check Intake charge pressure.
Refer to GROUP 15, On-vehicle Service - Intake Charge Pressure Check .
Are there any abnormalities?
Repair it. Then go to Step 7.
Go to Step 6.
 
STEP 6. Check the trouble symptoms.
(1) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle Pattern 7 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P0121 set?
Replace the ECM (Refer to Removal and Installation ). Then go to Step 7.
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .
 
STEP 7. Test the OBD-II drive cycle.
(1) Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle Pattern 7 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P0121 set?
Retry the troubleshooting.
The inspection is complete.