Circuit Description
The throttle position (TP) sensors 1 and 2 are located within the throttle body assembly. Each sensor has the following components:
| • | A 5-volt reference circuit |
| • | A low reference circuit |
| • | A signal circuit |
This provides the engine control module (ECM) with a signal voltage proportional to throttle plate movement. TP sensor 1 signal voltage at closed throttle is near the 5-volt reference and decreases as the throttle plate is opened. TP sensor 2 signal voltage at closed throttle is near the low reference and increases as the throttle plate is opened. If the ECM detects the TP sensor 1 signal voltage is not within the predicted range, DTC P0120 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0120 Throttle Position (TP) Sensor 1 Circuit
Conditions for Running the DTC
| • | The ignition switch is in the Crank or Run position. |
| • | DTC P0641 is not set. |
| • | The ignition voltage is greater than 5.23 volts. |
| • | DTC P0120 runs continuously when the above conditions are met. |
Conditions for Setting the DTC
The ECM detects that the TP sensor 1 voltage is less than 0.27 volt or more than 4.67 volts for more than 0.4 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 ECM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic runs and passes. |
| • | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using a scan tool. |
Step | Action | Values | 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 | |
2 | Are DTCs P0122 and P0123 also set? | -- | Go to Step 3 | |
3 |
Does the scan tool indicate voltage less than the first value or greater than the second value? | 0.27 V 4.67 V | Go to Step 6 | Go to Step 4 |
4 | Is DTC P2135 also set? | -- | Go to Step 5 | |
5 |
Did the DTC fail this ignition? | -- | Go to Step 6 | Go to Testing for Intermittent Conditions and Poor Connections |
6 |
Does the scan tool indicate voltage at the specified value? | 0 V | Go to Step 7 | Go to Step 12 |
7 |
Does the scan tool indicate the TP sensor 1 voltage at the specified value? | 5 V | Go to Step 8 | Go to Step 9 |
8 | Probe the TP sensor low reference circuit with a test lamp connected to B+. Does the test lamp illuminate? | -- | Go to Step 18 | Go to Step 14 |
9 | Measure the voltage of the TP sensor 1 5-volt reference circuit with a DMM. Does the DMM indicate voltage at the specified value? | 5 V | Go to Step 11 | Go to Step 10 |
10 | Does the DMM indicate voltage less than the specified value on the TP sensor 1 5-volt reference circuit? | 5 V | Go to Step 15 | Go to Step 17 |
11 | Test the TP sensor 1 signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 13 |
12 | Test the TP sensor 1 signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 20 |
13 | Test the TP sensor 1 signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 20 |
14 | Test the TP sensor 1 low reference circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 20 |
15 | Test the TP sensor 1 5-volt reference circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 16 |
16 | Test the TP sensor 1 5-volt reference circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 20 |
17 | Test the TP sensor 1 5-volt reference circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 22 | -- |
18 | Test for an intermittent and for a poor connection at the throttle body. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 19 |
19 | Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement . Did you complete the replacement? | -- | Go to Step 22 | -- |
20 | Test for an intermittent and for a poor connection at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs. Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 21 |
21 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 22 | -- |
22 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 23 |
23 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
