Circuit Description
The throttle position (TP) sensor contains a potentiometer whose resistance value changes with the changes in the throttle valve position. The powertrain control module (PCM) provides a 5 volt reference voltage to the TP sensor. The PCM reads the voltage across the TP sensor and converts the voltage into a throttle angle. The TP sensor resistance decreases as the throttle-valve opening increases, and the TP sensor resistance increases as the throttle-valve opening decreases. The TP sensor voltage that is being monitored by the PCM will increase as the throttle-valve opening increases.
Conditions for Setting the DTC
| • | A low voltage input is indicated at the PCM with the engine running. |
| • | Above condition is present for at least 0.5 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL). |
| • | The PCM records the operating conditions at the time that the diagnostic fails. The Freeze Frame buffer stores this information. |
| • | The PCM enters the Fail-Safe Function and assumes the throttle angle is 20 degrees while stopping ISC control. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns OFF after three consecutive passing trips without a fault present. |
| • | A History DTC clears after 40 consecutive warm-up cycles without a fault. |
| • | Use the Clear DTC Information function on the scan tool, or disconnect the PCM battery feed in order to clear the DTC. |
Diagnostic Aids
Check for any of the following conditions:
| • | A TP sensor that adjusted incorrectly, or a binding or a stuck throttle plate, may cause a DTC P0122 to set. Refer to Throttle Position Sensor Adjustment . |
| • | Check the resistance of the TP sensor. TP sensor resistance between terminals 1 and 4 should be 2.87 ohms to 5.33k ohms. TP sensor resistance between terminals 1 and 3 should be 100 ohms to 20k ohms. Replace the TP sensor if the measured resistance is not within the specified values. Refer to Throttle Position Sensor Replacement . |
| • | Check for an open reference circuit if a DTC P0107 and P0122 are set together. |
| • | A faulty electrical connection to the PCM. |
A fault in the TP sensor electrical circuit may cause an intermittent malfunction. Inspect the wiring harness and the components for any of the following conditions:
| • | Backed out terminals |
| • | Incorrect mating of terminals |
| • | Broken electrical connector locks |
| • | Incorrectly formed terminals or damaged terminals |
| • | Faulty terminal-to-wire connections |
| • | Physical damage to the wiring harness |
| • | A broken wire inside the insulation |
| • | Corrosion of electrical connections, of electrical splices, or of terminals |
If a DTC P0122 cannot be duplicated, the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was set.
Test Description
The numbers below refer to the step numbers in the Diagnostic Table.
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The Powertrain OBD system check prompts the technician to complete some basic checks, and to save the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data that was taken when the fault occurred. The scan tool saves the information for later reference.
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This step determines if a fault is present. The vehicle must be at operating temperature.
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The TP sensor adjustment must be checked and set to specifications. Replace the TP sensor if the correct adjustments cannot be made. Refer to Throttle Position Sensor Adjustment and Throttle Position Sensor Replacement to .
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Is the TP sensor percentage at the specified value or below the specified value? | 2% | |||
3 |
Is the TP sensor percentage at the specified value or below the specified value? | 2% | Go to Diagnostic Aids | |
4 |
Is the TP sensor signal voltage within the specified value? | 4 to 5 volts | ||
5 | Measure the voltage from the 5 volt reference circuit, on the harness side, to ground with the DMM. Is the voltage near the specified value? | 5.0 volts | ||
6 |
Was a repair necessary? | -- | ||
7 |
Was a repair necessary? | -- | ||
8 |
Was a repair necessary? | -- | ||
9 |
Was a repair necessary? | -- | ||
Adjust or replace the TP sensor. Refer to Throttle Position Sensor Adjustment and Throttle Position Sensor Replacement to . Is the action complete? | -- | -- | ||
11 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | |
12 |
Are any DTCs displayed on the scan tool? | -- | Go to the Applicable DTC Table | System OK |
