P0123
DTC P0123 Throttle/Pedal Position Sensor/Switch "A" Circuit High Input
COMPONENT 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 the Mass Air Flow Sensor (MAFS) signal along with the TPS signal to adjust fuel injection duration and ignition timing.
DTC DESCRIPTION
ECM sets DTC P0123 if the ECM detects signal voltage higher than the possible range of a properly operating TPS.
DTC Detecting Condition:
Schematic Diagram:
Signal Waveform:
MONITOR DTC STATUS
NOTE: If any codes relating to TPS or MAFS are stored, do ALL REPAIRS associated with those codes before proceeding with further troubleshooting
1. Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode.
2. Press F4(DTAL) to select DTC information from the DTCs menu.
3. Confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions.
4. Read "DTC Status" parameter.
5. Is parameter displayed "History (Not Present) fault"?
NOTE:
- History (Not Present) fault: DTC occurred but has been cleared.
- Present fault: DTC is occurring at present time.
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 loose or poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.
NO: Go to "Air Leakage Inspection" procedure.
TERMINAL AND CONNECTOR INSPECTION
1. Many malfunctions in the electrical system are caused by poor harness(es) 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 "Component Inspection" procedure.
GROUND CIRCUIT INSPECTION
1. Ignition "OFF".
2. Disconnect TPS connector.
3. Ignition "ON" & Engine "OFF".
4. Measure voltage between terminal 2 of the sensor harness connector and chassis ground.
Specification: Approx. 0 V
5. Is voltage within the specification?
YES: Go to step "Signal Circuit Inspection" procedure.
NO: Check the ground circuit for an open.
Repair as necessary and go to "Verification of Vehicle Repair" procedure.
SIGNAL CIRCUIT INSPECTION
1. With sensor connector still disconnected, measure voltage between terminal 3 of the sensor harness connector and chassis ground.
Specification: Approx. 5 V
2. Is voltage within the specification?
YES: Go to "Component Inspection" procedure.
NO:
- Possibility of open or short to power in signal circuit.
- Repair as necessary and go to "Verification of Vehicle Repair" procedure.
COMPONENT INSPECTION
1. Ignition "OFF".
2. Disconnect TPS connector.
3. Measure resistance between terminals 1 and 2 of the sensor connector(Component side).
Specification: Approx. 1.6 - 2.4 K ohms at all throttle position
4. With still TPS connector disconnected, measure resistance between terminals 2 and 3 of the sensor connector(Component 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: 0.71 - 1.38 K ohms at closed throttle valve, 2.7 K ohms at wide open throttle
6. Is resistance within the specification?
YES: Check for poor connection between ECM and component: backed out terminal, improper mating, broken locks or poor terminal to wire connection. Repair as necessary and go to "Verification of Vehicle Repair" procedure.
NO: Check TPS for contamination, deterioration, or damage. 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 Repair" procedure.
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. Press F4(DTAL) and confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions
3. Read "DTC Status" parameter.
4. Is parameter displayed "History (Not Present) fault"?
YES: System performing to specification at this time. Clear the DTC.
NO: Go to the applicable troubleshooting procedure.