Circuit Description
The throttle position (TP) sensor is a potentiometer. The control module supplies the TP sensor a reference voltage, a signal, and ground circuits. When the throttle is depressed, the TP sensor signal rises to near the reference voltage. When the throttle is released, the TP sensor signal decreases from the reference voltage. The control module monitors the TP sensor signal circuit voltage in order to determine the throttle blade angle, or opening.
This DTC determines if the TP sensor signal input to the vehicle control module (VCM) does not closely match the predicted value for the TP sensor. The VCM calculates TP signal voltage based on the engine RPM. If the TP sensor voltage and the predicted TP sensor values do not closely match, this DTC will be set.
Conditions for Running the DTC
| • | DTC P0122 is not active. |
| • | No IAC DTCs are active. |
| • | No MAP sensor DTCs are active. |
| • | The engine is running. |
| • | The BARO is not in default. |
| • | The throttle position is steady. |
Stuck High Test
The MAP is less than 50 kPa.
Stuck Low Test
| • | The "stuck high" test has passed. |
| • | The MAP is more than 65 kPa. |
| • | The IAC is between 10-340 counts. |
Conditions for Setting the DTC
The calculated throttle position is less than the actual throttle position for more than 5 seconds.
Stuck High Test
The throttle position is more than the calculated throttle position for more than 5 seconds.
Stuck Low Test
The throttle position is less than the calculated throttle position for more than 5 seconds.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles. |
| • | The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool Freeze Frame/Failure Records. |
Conditions for Clearing the MIL or DTC
| • | The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed. |
| • | A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle. |
| • | Use a scan tool in order to clear the DTCs. |
Diagnostic Aids
The scan tool displays the throttle position in volts. It should display approximately 0.45-0.85 volt with the throttle closed and with the ignition ON or at idle. The voltage should increase steadily as the throttle is moved toward wide open throttle (WOT).
The scan tool will read the throttle angle percentage. 0 percent at closed throttle. A reading of 100 percent indicates wide open throttle (WOT). A MAP-related DTC could set if the TP throttle angle is skewed or stuck at a value of less than 20 percent.
Check the condition of the connector and the sensor terminals for moisture or for corrosion, and clean or replace the terminals as necessary. If you find corrosion, check the condition of the connector seal and repair or replace the seal as necessary. If DTC P0121 is intermittent, refer to Symptoms .
Excessive throttle cable tension or excessive cruise control cable tension could result in this DTC.
An intermittent may be caused by any of the following conditions:
| • | A poor connection |
| • | Rubbed through wire insulation |
| • | A broken wire inside the insulation |
Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The throttle position (TP sensor has an auto-zeroing feature. If the voltage reading is approximately 0.2-0.9 volt, the VCM interprets that value as a closed throttle. If the reading is out of the auto zero range at the closed throttle, check for a binding throttle shaft or for a damaged linkage. If the throttle shaft and the linkage are OK, continue the diagnosis.
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The TP sensor throttle angle should range smoothly from 0-100 percent when the throttle is slowly depressed to the wide open throttle (WOT) position. If not, a skewed out-of-range TP sensor, a low reference voltage, or a faulty connection could be possible causes.
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With the TP sensor disconnected, the TP sensor signal voltage should go low if the VCM and the wiring are OK. DTC P0122 may set.
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Reference voltage that is less than 4.5 volts can cause a faulty TP performance condition. Check both of the 5-volt reference circuits for conditions that could cause low voltage on the TP sensor circuit.
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A TP sensor faulty performance condition could be caused by he throttle shaft, the throttle linkage, or the accelerator cable not closing because of sticking or binding .
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||
Is the throttle angle more than the specified value? | 2% | |||||||
|
Important: The engine must remain OFF for this step. Depress the throttle slowly to wide open throttle (WOT) while you observe the throttle angle increase through the specified range. Does the TP sensor range reach the maximum specified value? | 0-100% | |||||||
4 | Release the throttle. Is the throttle angle more than the specified value? | 2% | ||||||
5 | The DTC is intermittent. Are any additional DTCs set? | -- | Go to applicable DTC | Go to Diagnostic Aids | ||||
Disconnect the TP sensor harness connector. Is the TP sensor at the specified value? | 0 V | |||||||
7 |
Is the test lamp ON? | -- | ||||||
8 |
Is the voltage more than the specified value? | 5.2 V | ||||||
9 |
Is the voltage more than the specified value? | 0 V | ||||||
10 |
Is the throttle angle at the specified value? | 100% | ||||||
11 |
Is the voltage near the specified value? | 5.2 V | ||||||
12 |
Is the resistance near the specified value? | 0ohms | ||||||
13 | Repair the short to voltage on the TP sensor signal circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||
14 | Repair the open in the TP sensor ground circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||
15 | Repair the short to voltage in the 5-volt reference circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||
Repair the low voltage condition on the 5-volt reference circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | ||||||
17 | Check for a faulty connection at the TP sensor. Did you find a problem? | -- | ||||||
18 | Repair the circuit as necessary. Refer to Wiring Repairs or Connector Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||
Check the throttle shaft, the linkage, the throttle, and the cruise cables for:
Did you find a problem? | -- | |||||||
20 | Repair the throttle shaft, the linkage, or the cables as necessary. Is the action complete? | -- | -- | |||||
21 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Is the action complete? | -- | -- | |||||
22 | Check for a faulty connection at the VCM. Repair the connection as necessary. Refer to Connector Repairs in Wiring Systems. Did you find a problem? | -- | ||||||
23 |
Important: The replacement VCM must be programmed. Replace the VCM. Refer to VCM Replacement/Programming . Is the action complete? | -- | -- | |||||
24 |
Does the scan tool indicate the diagnostic passed? | -- | ||||||
25 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to applicable DTC | System OK |
