Circuit Description
The throttle body assembly contains 2 throttle position (TP) sensors. The TP sensors are mounted to the throttle body assembly and are not serviceable. The TP sensors provide a signal voltage that changes relative to throttle blade angle. The engine control module (ECM) supplies the TP sensors with a common 5-volt reference circuit, a common low reference circuit, and 2 independent signal circuits.
The TP sensors have opposite functionality. TP sensor 1 signal voltage decreases from above 4 volts at idle to below 1 volt at wide open throttle (WOT). TP sensor 2 signal voltage increases from below 1 volt at idle to above 4 volts at WOT.
If the ECM detects TP sensor 1 signal voltage is too low or too high, this DTC sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0120 Throttle Position (TP) Sensor 1 Circuit
Conditions for Running the DTC
| • | DTCs P0341, P0351, P0601, P0602, P0603, P0604, P0606, P0607 are not set. |
| • | The ignition is ON, with the engine OFF, or the engine is operating. |
| • | The ignition 1 voltage is more than 5.23 volts. |
| • | DTC P0120 runs continuously once the above conditions are met. |
Conditions for Setting the DTC
The ECM detects the TP sensor 1 signal voltage is less than 0.275 volts for less than 1 second.
The ECM detects the TP sensor 1 signal voltage is more than 4.725 volts for less than 1 second.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records. |
| • | The control module commands the TAC system to operate in the Reduced Engine Power mode. |
| • | A message center or an indicator displays Reduced Engine Power. |
| • | Under certain conditions the control module commands the engine OFF. |
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
| • | Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector. |
| • | If there is a condition with the TP sensors, the ECM defaults to reduced power mode for the entire ignition cycle, even if the condition is corrected. |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls 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 |
Are any other DTCs set? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to DTC P0121 | |
