P0121
DTC P0121 THROTTLE/PEDAL POSITION SENSOR/SWITCH "A" CIRCUIT RANGE/PERFORMANCEComponent Location:
COMPONENT LOCATION
GENERAL DESCRIPTION
Throttle Position (TP) Sensor measures the opening angle of throttle valve and mounted on the side of the throttle body and is connected to the throttle blade shaft. The TP sensor's resistance changes according to the throttle blade shaft position. TP Sensor has a potentiometer whose resistance changes along with the Throttle valve position. The Powertrain Control Module (PCM) provides a 5 volt reference voltage to the TP Sensor. The PCM reads the voltage across the TP Sensor and converts it into throttle position. During acceleration, the TP Sensor resistance decreases. During deceleration, the TP Sensor resistance increases. The PCM uses the TP Sensor signal to adjust timing and injector pulse width. The TP Sensor signal along with the MAF sensor signal is used by the PCM to calculate engine load. Throttle angle information to the PCM to be used for the detection of engine status such as idle, part load, full throttle, and acceleration fuel enrichment.
DTC DESCRIPTION
If the sensor output voltage is out of threshold value, the PCM determines that a malfunction exists and a DTC is stored.
DTC Detecting Condition:
Schematic Diagram:
Signal Waveform & Data:
MONITOR SCANTOOL DATA
1. Ignition "OFF" & Engine "OFF"
2. Install Scantool then, Ignition "ON" & Engine "OFF".
3. Monitor "TPS VALUE" parameter on CURRENT DATA.
Specification
Throttle valve fully closed: Approx. 0.2 - 0.8 V
Throttle valve fully open: Approx. 4.0 - 4.4 V
TP sensor signal should increase smoothly as throttle is opened.
4. Is Current data displayed correctly?
YES: Fault is intermittent caused by poor contact in the sensor's and/or PCM's connector or was repaired and PCM 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 "Component Inspection" procedure.
COMPONENT INSPECTION
1. Check TPS Performance Test
1. Ignition "ON" & Engine "ON"
2. Install Scantool and select the "TP SENSOR" parameter on the CURRENT DATA.
3. Monitor signal waveform of the "TP SENSOR" on the Scantool.
Specification: TPS value changes smoothly in proportion with the MAFS.
4. Is the TPS value within specification?
YES: Check TPS for contamination, deterioration, or damage. Clean TPS with suitable cleaner as necessary and let air dry before reinstalling. If problem still exists, test with a new TP sensor and check for proper operation. If problem is corrected, replace TPS sensor and go to "Verification vehicle Repair" procedure.
NO: Go to "Check TPS resistance" as below.
2. Check TPS resistance.
1. Ignition "OFF" & Engine "OFF"
2. Disconnect TPS connector.
3. Measure resistance between terminals 1 and 2 of the TPS connector. (to TP sensor side).
Specification: Approx. 3.5 - 6.5 Ohms (with throttle valve fully closed) at 20 °C (68 °F)
4. With still TPS connector disconnected, measure resistance between terminals 1 and 3 of the sensor connector(To sensor side).
5. Operate the throttle valve slowly from the idle position to the full open position and check the resistance changes smoothly in proportion with the throttle valve opening angle.
Specification: Resistance changes smoothly in proportion with the throttle valve opening angle.
6. Is the measured resistance within specification?
YES: Go to "Check PCM" as below.
NO: Substitute with a known - good TPS and check for proper operation. If the problem is corrected,replace TPS and go to "Verification of Vehicle Repair" procedure.
3. Check PCM
1. Ignition "OFF" & Ignition "ON"
2. Connect Scantool and Ignition "ON"
3. Select simulation function on scantool.
4. Simulate voltage at terminal 3 of TP sensor signal connector.
5. Is TP sensor signal value changed according to simulation voltage?
YES: Fault is intermittent caused by poor contact in the sensor's and/or PCM's connector. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification vehicle Repair" procedure.
NO: Substitute with a known - good PCM and check for proper operation.
If the problem is corrected, replace PCM and go to "Verification of Vehicle Repair" procedure.
VERIFICATION OF VEHICLE REPAIR
After a repair, it is essential to verify that the fault has been corrected.
1. Monitor and record the Freeze Frame Data for the Diagnostic Trouble Code(DTC) which has been diagnosed.
2. Using a Scantool, Clear the DTCs.
3. Operate the vehicle within conditions noted in the freeze frame data or enable conditions.
4. Monitor that all readiness tests have been verified as "Complete"
5. Are any DTCs present?
YES: Go to the applicable troubleshooting procedure.
NO: System is performing to specification at this time.