Circuit Description
The throttle position (TP) sensor is a potentiometer. The powertrain control module (PCM) supplies the TP sensor a reference voltage, a signal, and low reference 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 diagnostic trouble code (DTC) determines if the throttle position (TP) sensor signal input to the powertrain control module (PCM) does not closely match what the predicted value for the TP sensor should be. The PCM calculates what the TP signal voltage should be based on 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
| • | DTCs P0112, P0113, P0122, P0506, or P0507 are not set. |
| • | The engine is running. |
| • | The barometric pressure (BARO) is not in default. |
| • | The throttle position is steady. |
Conditions for Setting the DTC
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) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
The scan tool displays the throttle position in volts. The scan tool should display about 0.45-0.85 volts with the throttle closed and the ignition ON or at idle. The voltage should increase at a steady rate as the throttle is moved toward wide open throttle (WOT).
The scan tool will read the throttle angle percentage. 0 percent equals closed throttle. 100 percent equals wide open throttle (WOT).
Inspect the condition of the connector and the sensor terminals for moisture or corrosion, and clean or replace the terminals as necessary. If corrosion is found, inspect the condition of the connector seal and repair or replace the seal as necessary. If DTC P0121 is intermittent, refer to Symptoms - Engine Controls .
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.
-
The TP sensor has an auto zeroing feature. If the voltage reading is within the range of about 0.2-0.9 volt, the PCM uses 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 a damaged linkage. If the throttle shaft and the linkage are okay, continue with the diagnosis.
-
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, low reference voltage or a poor connection could be possible causes.
-
With the TP sensor disconnected, the TP sensor signal voltage should go low if the PCM and the wiring are okay and a DTC P0122 may set.
-
Reference voltage less than 4.5 volts could cause a poor TP performance condition. Be sure to check both 5-volt reference circuits for conditions that could cause low voltage on the TP sensor circuit.
-
The throttle shaft, throttle linkage, or accelerator cable not closing due to sticking or binding could cause a TP sensor poor performance condition.
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||
1 |
Important: Before clearing the DTCs, use the scan tool Capture Info to save the Freeze Frame/Failure Records for reference. The control modules data is deleted once the Clear Info function is used. Did you perform the Diagnostic System Check-Engine Controls ? | -- | Go to Step 2 | |||||
Does the scan tool display the throttle angle more than the specified value? | 2% | Go to Step 6 | Go to Step 3 | |||||
|
Important: The engine must remain OFF for this step. Depress the throttle slowly to wide open throttle (WOT) while watching the throttle angle increase through the specified range. Does the TP sensor range reach the maximum specified value? | 0-100% | Go to Step 4 | Go to Step 10 | |||||
4 | Release the throttle. Does the scan tool display the throttle angle more than the specified value? | 2% | Go to Step 6 | Go to Step 5 | ||||
5 | The DTC is intermittent. Are any additional DTCs set? | -- | Go to Diagnostic Aids | |||||
Disconnect the TP sensor harness connector. Does the scan tool display the TP sensor at the specified value? | 0 V | Go to Step 7 | Go to Step 9 | |||||
7 |
Is the test lamp ON? | -- | Go to Step 8 | Go to Step 14 | ||||
8 |
Is the voltage more than the specified value? | 5.2 V | Go to Step 15 | Go to Step 19 | ||||
9 |
Is the voltage more than the specified value? | 0 V | Go to Step 13 | Go to Step 22 | ||||
10 |
Does the scan tool display the throttle angle at the specified value? | 100% | Go to Step 17 | Go to Step 11 | ||||
11 |
Is the voltage near the specified value? | 5.2 V | Go to Step 12 | Go to Step 16 | ||||
12 |
Is the resistance near the specified value? | 0 ohms | Go to Step 22 | Go to Step 18 | ||||
13 | Repair the short to voltage on the TP sensor signal circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 24 | -- | ||||
14 | Repair the open in the TP sensor ground circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 24 | -- | ||||
15 | Repair the short to voltage in the 5-volt reference circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 24 | -- | ||||
Repair the low voltage condition on the 5-volt reference circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 24 | -- | |||||
17 | Check for a poor connection at the TP sensor. Did you find a problem? | -- | Go to Step 18 | Go to Step 19 | ||||
18 | Repair the circuit as necessary. Refer to Wiring Repairs or Connector Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 24 | -- | ||||
Check the throttle shaft, linkage, throttle and cruise cables for the following conditions:
Did you find a problem? | -- | Go to Step 20 | Go to Step 21 | |||||
20 | Repair the throttle shaft, linkage, or cables as necessary. Is the action complete? | -- | Go to Step 24 | -- | ||||
21 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Is the action complete? | -- | Go to Step 24 | -- | ||||
22 |
Did you find a problem? | -- | Go to Step 24 | Go to Step 23 | ||||
23 |
Is the action complete? | -- | Go to Step 24 | -- | ||||
24 |
Does the scan tool indicate the diagnostic Passed? | -- | Go to Step 25 | Go to Step 2 | ||||
25 | Does the scan tool display any additional undiagnosed DTCs? | -- | System OK | |||||
