P0121
P0121Component Location:
General Description
The Throttle Position Sensor (TPS) is mounted on the throttle body and detects the opening angle of the throttle plate. The TPS has a variable resistor (potentiometer) whose characteristic is the resistance changing according to the throttle angle. During acceleration, the TPS resistance between the reference 5 V and the signal terminal decreases and output voltage increases; during deceleration, the TPS resistance increases and TPS output voltage decreases. The ECM supplies a reference 5 V to the TPS and the output voltage increases directly with the opening of the throttle valve. The TPS output voltage will vary from 0.2 - 0.8 V at closed throttle to 4.3 - 4.8 V at wide-open throttle. The ECM determines operating conditions such as idle (closed throttle), part load, acceleration/deceleration, and wide-open throttle from the TPS. Also The ECM uses Manifold Absolute Pressure Sensor (MAPS) signal along with the TPS signal to adjust fuel injection duration and ignition timing.
DTC Description
Once enable conditions are met, if the number of times that the throttle angle input signal rapidly increases over 30% is greater than or equal to 3, P0121 is set.
DTC Detecting Condition:
Specification:
Signal Waveform:
Schematic Diagram:
Monitor Scantool Data
1. Connect scantool to Data Link Connector (DLC).
2. Warm up the engine to normal operating temperature.
3. Monitor the "TPS" parameters on the scantool.
4. Are the parameters displayed correctly?
YES - Fault is intermittent caused by poor contact in the sensor's and/or ECM's connector or was repaired and ECM memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of vehicle Repair" procedure.
NO - Go to "Terminal & Connector Inspection" procedure
Terminal and Connector Inspection
1. Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
2. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.
3. Has a problem been found?
YES - Repair as necessary and go to "Verification of Vehicle Repair" procedure.
NO - Go to "TPS circuit inspection" procedure.
TPS Circuit Inspection
4. Key "OFF".
5. Disconnect TPS connector.
6. Key "ON".
7. Measure the voltage between terminal 1, 2, 3 of TPS harness connector and chassis ground.
Specification :
Terminal 1 : Approx. 5 V
Terminal 2 : Approx. 5 V
Terminal 3 : Approx. 0 V
8. Is the measured voltage within specifications?
YES - Go to "Component inspection" procedure
NO - Check for Open or Short in TPS circuit. Repair as necessary and then go to "Verification of Vehicle Repair" procedure.
Component Inspection
1. Check TPS resistance
1. IG "OFF".
2. Disconnect TPS connector.
3. Measure the resistance between terminal 2 and 3 of TPS component side.
Specification :
4. Is the measured resistance within specification?
YES - Go to "Check ECM" as follows
NO - Substitute with a known-good TPS and check for proper operation. If the problem is corrected, replace TPS and then go to "Verification of Vehicle.
2. Check ECM
1. Key "OFF".
2. Connect the scantool and select "Simulation SCAN" in the menu.
3. Connect channel A of scantool with terminal 1 of TPS harness connector, and key "ON".
4. Simulate voltage at signal line.
5. Does the signal output of TPS change according to simulation voltage?
YES - Thoroughly check connectors for looseness, poor connection, bending, corrosion,contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.
NO - Substitute with a known - good ECM and check for proper operation. If the problem is corrected, replace ECM and go to "Verification of Vehicle Repair" procedure.
NOTE: There is a memory reset function on scantool that can erase optional parts automatically detected and memorized by PCM. Before or after testing PCM on the vehicle, use this function to reuse the PCM on the others
Verification of Vehicle Repair
After a repair, it is essential to verify that the fault has been corrected.
1. Connect scan tool and select "Diagnostic Trouble Codes (DTCs)" mode.
2. Clear the DTCs and Operate the vehicle within DTC Enable conditions in General information.
3. Are any DTCs present?
YES - Go to the applicable troubleshooting procedure.
NO - System is performing to specification at this time.