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 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 diagnostic trouble code (DTC) is designed to detect intermittent low signal voltage on the TP sensor signal circuit.
Conditions for Running The DTC
The engine is running.
Conditions for Setting The DTC
The TP sensor voltage is less than 0.25 volts for less than 1 second.
Action Taken When the DTC Sets
| • | The control module stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records. |
| • | The driver information center, if equipped, may display a message. |
Conditions for Clearing the DTC
| • | 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 non-emission related diagnostic. |
| • | Clear the DTC with a scan tool. |
Diagnostic Aids
The scan tool reads throttle position in volts. The TP should read between 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 the wide open throttle (WOT) position.
Also, some scan tools will read the throttle angle. 0 percent equals closed throttle and 100 percent equals WOT.
An intermittent open or short to ground in the 5-volt reference circuit or the TP sensor signal circuit could result in a DTC P1122. If a low voltage reading is present, additional sensor circuit voltage codes could be set. Refer to any non-intermittent DTCs that are set.
Observe the TP sensor while depressing the accelerator pedal with the ignition turned ON, leaving the engine OFF. The display should vary from about 0.5 volts (500 mV) with the throttle closed, to more than 4.5 volts (4,500 mV) when throttle is held at the wide open throttle (WOT) position.
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 number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
Is the TP sensor voltage less than the specified value? | 0.25 V | Go to DTC P0122 | Go to Step 3 | |
3 |
Did you find a problem? | -- | Go to Step 6 | Go to Step 4 |
4 |
Did you find a problem? | -- | Go to Step 6 | Go to Step 5 |
5 |
Did the voltage decrease? | -- | Go to Step 6 | Go to Diagnostic Aids |
6 | Repair the circuit as necessary. Refer to Wiring Repairs or Connector Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 7 | -- |
7 |
Does the scan tool indicate the diagnostic Passed? | -- | Go to Step 8 | Go to Step 2 |
8 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to the applicable DTC table | System OK |
