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 three circuits:
| • | 5-volt reference circuit |
| • | Low reference circuit |
| • | Signal circuit |
The PCM provides the TP sensor with a 5-volt reference circuit and a 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 greater than 4 volts through the TP sensor signal circuit. If the PCM detects an excessively high signal voltage, this diagnostic trouble code (DTC) will set.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
| • | The TP sensor signal voltage is more than 4.9 volts. |
| • | The above conditions are present for longer than 1 second. |
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 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 | |
2 |
Does the scan tool indicate that the TP sensor voltage is greater than the specified value? | 4.9 V | Go to Step 4 | Go to Step 3 |
3 |
Does the DTC fail this ignition? | -- | Go to Step 4 | Go to DTC P1121 |
4 |
Does the scan tool indicate that the TP voltage is at the specified value? | 0 V | Go to Step 5 | Go to Step 8 |
5 | With a DMM, test the TP sensor 5-volt reference circuit for voltage. Does the DMM indicate that the TP voltage parameter is at the specified value? | 5 V | Go to Step 6 | Go to Step 9 |
6 | Connect a test lamp between the TP sensor low reference circuit and battery positive voltage. Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 7 |
7 | Test the low reference circuit of the TP sensor for a high resistance or 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 15 |
8 | Test the signal circuit of the TP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 15 |
9 | Test all 5-volt reference circuits for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 10 |
Did you observe a change in voltage while commanding the EGR? | -- | Go to Step 11 | Go to Step 14 | |
11 |
Did you observe a change in voltage while commanding the EGR? | -- | Go to Step 13 | Go to Step 12 |
12 | Replace the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement . Did you complete the replacement? | -- | Go to Step 17 | -- |
13 | Repair the short between the EGR solenoid control circuit and the 5-volt reference circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 18 | -- |
14 | Inspect for poor connections at the harness connector of the TP sensor. 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 16 |
15 | Inspect for poor connections at the harness connector of 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 |
16 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- |
17 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 18 | -- |
18 |
Does the DTC run and pass? | -- | Go to Step 19 | Go to Step 2 |
19 | With a scan tool, observe the stored information, Capture info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
