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DTC P0121-00: Throttle Position Sensor (main) plausibility check
 
 
 
 
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.
 
 
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 difference between the actual volumetric efficiency and the volumetric efficiency estimated by the throttle position sensor (main) is higher than 0 percent. Or, the volumetric efficiency is 60 percent or lower.
  • Engine speed is 750 r/min or higher.
Judgment Criteria
  • For 0.4 second, the difference between the actual volumetric efficiency and the volumetric efficiency estimated by the throttle position sensor (main) is higher than 33 percent.
  • 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 higher.
Logic Flow Chart
Check Conditions
  • The difference between the actual manifold pressure and the manifold pressure estimated by the throttle position sensor (main) 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 more than 40 kPa (11.8 in.Hg).
  • 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 1 OBD- II DRIVE CYCLE.
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
  • Throttle position sensor (main) system failed.
  • Intake system vacuum leak.
  • There is some foreign matter around mass airflow sensor.
  • ECM failed.
 
 
DIAGNOSIS
Required Special Tools:
  • MB992744: Vehicle communication interface-Lite (V.C.I.-Lite)
  • MB992745: V.C.I.-Lite main harness A
  • MB992747: V.C.I.-Lite USB cable short
  • MB992748: V.C.I.-Lite USB cable long
1.STEP 1. Using scan tool (M.U.T.-III SE), read the DTC.
Use scan tool (M.U.T.-III SE) to check and see if a DTC other than P0121-00 is set.
Q: Is DTC other than P0121-00 set?
Perform troubleshooting for the set DTC (Refer to DIAGNOSTIC TROUBLE CODE CHART).
 
2.STEP 2. Using scan tool (M.U.T.-III SE), check the data list.
Use scan tool (M.U.T.-III SE) to check the data list (Refer to DATA LIST REFERENCE TABLE).
  • Item number 90: TPS (Main)
Q: Is the check result normal?
Perform troubleshooting for the throttle position sensor (main) circuit [Refer to DTC P0122-00: Throttle Position Sensor (main) circuit low input DTC P0122-00: Throttle Position Sensor (main) circuit low input), and Refer to DTC P0123-00: Throttle Position Sensor (main) circuit high input DTC P0123-00: Throttle Position Sensor (main) circuit high input)].
 
3.STEP 3. Check for intake system vacuum leak.
Q: Are there any abnormalities?
Repair it.
 
4.STEP 4. Check for foreign matter being around the mass airflow sensor.
Q: Are there any foreign matter?
Repair it.
 
5.STEP 5. Test the OBD-II drive cycle.
After erasing the DTC, carry out test drive with the drive cycle pattern, and recheck the DTC.
(1) Use scan tool (M.U.T.-III SE) to erase the DTC.
(2) Carry out test drive with the drive cycle pattern (Refer to Diagnostic Function, OBD-II Drive Cycle – Pattern 1 OBD- II DRIVE CYCLE).
(3) Use scan tool (M.U.T.-III SE) to recheck the DTC.
Q: Is DTC P0121-00 set?
Replace the ECM (Refer to ENGINE CONTROL MODULE (ECM) REMOVAL AND INSTALLATION).
Intermittent malfunction (Refer to GENERAL INFORMATION, General Information – How to Use Troubleshooting/Inspection Service Points – How to Cope with Intermittent Malfunctions HOW TO COPE WITH INTERMITTENT MALFUNCTIONS).