Circuit Description
The throttle position (TP) sensor is used by the powertrain control module PCM in order to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer sensor with a 5-volt reference circuit, a low reference circuit, and a signal circuit. Rotation of the TP sensor from the closed throttle position to the wide open throttle (WOT) position provides the PCM with a signal voltage from below 1 volt to more than 4 volts through the TP sensor signal circuit. If the PCM detects an excessively high signal voltage, this DTC will set.
DTC Descriptors
This diagnostic procedure supports the following DTC.
DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage
Conditions for Running The DTC
The ignition is ON.
Conditions for Setting The DTC
| • | The TP sensor signal voltage is more than 4.8 volts. |
| • | The condition exists for 10 seconds. |
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. |
Diagnostic Aids
| • | The PCM 5-volt reference circuits are internally connected within the PCM. If all the TP sensor circuits are OK, inspect the MAP sensor for malfunctions. |
| • | If the DTC occurs intermittently, performing the DTC P1121 diagnostic test may isolate the cause of the fault. Refer to DTC P1121 . |
| • | For an intermittent condition , refer to Intermittent Conditions . |
Test Description
The number below refers to the step number on the diagnostic table.
-
This step verifies that a condition exists.
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This step tests the signal circuit for a short to voltage. If scan tool displays a voltage after the TP sensor is disconnected, the circuit is shorted to a voltage.
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This step isolates the condition. Test the 5 volt reference circuit for a short to voltage if the measured voltage is more than the specified value.
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This step isolates the condition. Test the low reference circuit for an open or high resistance if the measured voltage is less than the specified value.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
Does the scan tool indicate that the TP sensor voltage is less than the specified value? | 4.8 V | Go to Step 3 | Go to Step 4 | |
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to DTC P1122 |
Does the scan tool indicate that the TP voltage is less than the specified value? | 0.2 V | Go to Step 5 | Go to Step 8 | |
Measure the voltage between the 5-volt reference circuit and the low reference circuit of the TP sensor with a DMM. Is the voltage less than the specified value? | 5.2 V | Go to Step 6 | Go to Step 9 | |
Is the voltage less than the specified value? | 4.8 V | Go to Step 7 | Go to Step 10 | |
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 14 | Go to Step 11 |
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 14 | Go to Step 11 |
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 14 | Go to Step 11 |
10 | Test for an intermittent and for a poor connection at the TP sensor harness connector. 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 14 | Go to Step 12 |
11 | Test for an intermittent and for a poor connection at the PCM harness connector. 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 14 | Go to Step 13 |
12 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
13 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
14 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 15 |
15 | Observe the Capture Info with a scan tool. Are there any DTCs that you have not diagnosed? | -- | System OK | |
