Circuit Description
The throttle position (TP) sensor is used by the powertrain control module (PCM) to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with 3 circuits:
| • | A 5-volt reference circuit |
| • | A low reference circuit |
| • | A TP sensor signal circuit |
The PCM provides the TP sensor with 5 volts on the 5-volt reference circuit and a ground on the low reference circuit. Rotation of the TP sensor rotor from the closed throttle position to the wide open throttle (WOT) position provides the PCM with a signal voltage from less than 1 volt to more than 4 volts through the TP sensor signal circuit. If the PCM detects an excessively low signal voltage, DTC P0122 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0122 Throttle Position (TP) Sensor 1 Circuit Low Voltage
Conditions for Running the DTC
| • | The engine is running. |
| • | DTC P0122 runs continuously when the above condition is met. |
Conditions for Setting the DTC
The PCM detects that the TP sensor voltage is less than 0.10 volt for more than 2 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. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
The measurement noted in this step will be used in subsequent steps if the measurement is not less than the specified value.
-
This step calculates the resistance in the 5-volt reference circuit.
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views | ||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||
2 |
Is the voltage less than the specified value? | 0.10 V | Go to Step 4 | Go to Step 3 | ||||||
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions | ||||||
4 |
Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 5 | ||||||
Is the voltage more than the specified value? | 4.8 V | Go to Step 8 | Go to Step 6 | |||||||
6 |
Does the voltage measure more than the specified value after either of the sensors are disconnected? | 4.8 V | Go to Step 15 | Go to Step 7 | ||||||
7 |
Is the voltage more than the specified value? | 4.8 V | Go to Step 10 | Go to Step 13 | ||||||
Important: Before any calculations are performed, ensure that all measurements are converted to like units. For example, volts/amps or millivolts/milliamps. Is the result more than the specified value? | 5 ohms | Go to Step 11 | Go to Step 9 | |||||||
9 |
Is the voltage more than the specified value? | 4.9 V | Go to Step 16 | Go to Step 12 | ||||||
10 | Test the 5-volt reference circuit between the powertrain control module (PCM) and the TP sensor for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 14 | ||||||
11 | Test the 5-volt reference circuit between the PCM and the TP sensor for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 14 | ||||||
12 | Test the TP sensor signal circuit between the PCM and the TP sensor for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 14 | ||||||
13 | Test the 5-volt reference circuits of the following sensors for a short to ground:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 14 | ||||||
14 | Test for shorted terminals and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 17 | ||||||
15 | Replace the component for which the voltage changed. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in Heating, Ventilation, and Air Conditioning or Fuel Tank Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 18 | -- | ||||||
16 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 18 | -- | ||||||
17 | Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 18 | -- | ||||||
18 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 19 | ||||||
19 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK | ||||||
