Circuit Description
The throttle position (TP) sensor is a 3 wire variable resistor called a potentiometer. The powertrain control module (PCM) supplies a 5.0 volt reference, a signal and a ground circuit to the sensor. The TP sensor sends a voltage signal back to the PCM relative to the throttle plate opening. The voltage will vary from approximately 0.35 volts at closed throttle, to over 4.65 volts at wide open throttle (WOT).
Conditions for Running the DTC
| • | DTCs P0107 or P0108 are not set. |
| • | MAP is less than 60 kPa. |
| • | Engine speed is less than 1500 RPM. |
| Or |
| • | DTCs P0107 or P0108 not set. |
Conditions for Setting the DTC
The TP sensor voltage is more than 3.9 volts for 13.75 seconds when the engine speed is less than 1500 RPM.
Or
TP sensor voltage is more than 4.8 volts for 13.75 seconds when engine speed is more than 1500 RPM.
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) illuminates after 2 consecutive ignition cycles with the malfunction present. |
| • | The PCM records the operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers stores this information. |
| • | A history DTC is stored. |
| • | The TP angle will default to 0 percent when the vehicle speed is less than 2 mph. The TP angle defaults to 10 percent when the vehicle speed is more than 2 mph. The scan tool shows the defaulted value. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after 3 consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm up cycles without a fault. |
| • | A scan tool can clear the DTCs. |
Diagnostic Aids
The TP should read about 0.45 to 0.85 volts with the throttle closed and the ignition ON or at idle. The voltage should increase at a steady rate as the throttle is moved toward WOT. A short to voltage on the signal or the 5 volt reference, or an open ground circuit will result in a DTC P0123. Scan the TP sensor while depressing the throttle with the engine OFF and the ignition ON. The voltage should vary from below 1.25 volts to over 4.5 volts with the throttle at WOT.
Whenever this DTC cannot be duplicated, use the information included in the Freeze Frame data in order to duplicate the conditions when the DTC set. Thoroughly check any circuits or components suspected of causing an intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems for information on testing.
A faulty A/C pressure sensor circuit or sensor could cause DTC P0123 to set. Disconnect the A/C electrical connector. If the TP reading returns to normal, diagnose the A/C refrigerant sensor circuit.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the Freeze Frame and Failure Records data on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The scan tool stores this data for later reference.
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With the throttle closed, the TP sensor voltage should read less than 0.80 volts. If the TP sensor voltage does not read less than 0.80 volts, check for a binding or a sticking throttle cable.
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The PCM and the wiring are OK if the TP sensor voltage is less than 0.3 volts with the TP sensor electrical connector disconnected.
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Probing the ground circuit with a test lamp checks the circuit for high resistance which will cause a DTC P0123 to set.
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Important: The powertrain control module (PCM) uses a single internal 5.0 volt power supply to supply power to all the engine control components. If one component shorts the 5.0 volt reference circuit to ground or battery voltage, the other 5.0 volt reference circuits will also have a low or high voltage.
A shorted 5.0 volt reference circuit will also set additional DTCs.
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Reprogram the replacement PCM and perform the Crankshaft Position System Variation Learn Procedure. Refer to the latest Techline information for PCM programming .
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Is the TP sensor voltage more than the specified value? | 0.8 V | |||
3 |
Is the TP sensor voltage more than the specified value? | 3.9 V | Go to Diagnostic Aids | |
Is the TP sensor voltage less than the specified value? | 0.3 V | |||
Does the test lamp illuminate? | -- | |||
6 |
Was a repair necessary? | -- | ||
Was a repair necessary? | -- | |||
8 | Check the TP sensor electrical connector for a poor electrical connection and repair as necessary. Refer to Connector Repairs in Wiring Systems. Was a repair necessary? | -- | ||
9 |
Was a repair necessary? | -- | ||
10 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Is the action complete? | -- | -- | |
11 | Check for a poor electrical connection at the PCM electrical connector and repair as necessary. Refer to Connector Repairs in Wiring Systems. Did you find a condition? | -- | ||
|
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||
13 |
Does the scan tool indicate that the diagnostic Ran and Passed? | -- | ||
14 | Check to see if any additional DTCs are set. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to applicable DTC table | System OK |
