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 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.
The 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 in history after the first failure but will not illuminate the malfunction indicator lamp (MIL). |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores the failure information in the scan tools Freeze Frame/Failure Records. |
Conditions for Clearing the MIL/DTC
| • | 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 temperature exceeds 70°C (160°F) during the same ignition cycle. |
| • | Use the scan tool Clear Information function. |
Diagnostic Aids
The scan tool reads throttle position in volts. The TP should read 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).
Also, some scan tools will read the throttle angle. Zero percent equals closed throttle. One hundred 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 the 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) when throttle was closed, to over 4.5 volts (4,500 mV) when throttle is held at the 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 numbers below refer to the step numbers on the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | |
Is the TP sensor voltage less than the specified value? | 0.25 V | Go to DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage | 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 |
