Circuit Description
The Powertrain Control Module (PCM) supplies a 5.0 V reference signal and a ground to the throttle position (TP) 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 V at closed throttle, to more than 4.65 V at wide open throttle (WOT).
Conditions for Running the DTC
| • | A DTC P0107 or a DTC P0108 is not set. |
| • | The engine is running. |
| • | The manifold absolute pressure (MAP) is less than 60 kPa. |
| • | The engine speed is less than 1500 RPM. |
| OR: |
| • | A DTC P0107 or a DTC P0108 is not set. |
| • | The engine is running. |
| • | The MAP is more than 60 kPa. |
| • | The engine speed is more than 1500 RPM. |
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: |
| • | The TP sensor voltage is more than 4.8 volts when the engine speed is more than 1500 RPM. |
Action Taken When the DTC Sets
| • | The Malfunction Indicator Lamp (MIL) will illuminate after 2 consecutive ignition cycles in which the diagnostic runs with the fault active. |
| • | The PCM will record the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers. |
| • | A history DTC stores. |
| • | The coolant fan turns on. |
| • | The TP angle will default to 0 percent when the vehicle speed is less than 3 km/h (2 mph) and 10 percent when the vehicle speed is more than 3 km/h (2 mph). The scan tool will display 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. |
| • | Use a scan tool to clear the DTCs. |
Diagnostic Aids
If a DTC P0123 cannot be duplicated, the information included in the Freeze Frame data can be useful. Use the scan tool DTC information data to determine the status of the DTC. If the DTC occurs intermittently, use the DTC P0105 diagnostic table in order to help isolate the problem.
With the ignition on, the engine off, and the throttle at closed position, the voltage should measure between 0.20 V and 0.90 V and increase steadily to over 4.5 V at wide open throttle (WOT).
Test Description
The numbers below refer to step numbers on the diagnostic table.
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With the throttle closed, the TP sensor voltage should measure less than 0.80 volts. If the TP sensor voltage does not measure 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 disconnected.
-
Probing the ground circuit with a test lamp checks the circuit for a high resistance which will cause DTC P0123 to set.
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Important: The 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 to B+, 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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The replacement PCM must be programmed and the Crankshaft Position System Variation Learn procedure must be preformed.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | |
Is the TP sensor voltage more than the specified value? | 0.8 V | Go to Step 4 | Go to Step 3 | |
3 |
Does the DTC reset? | -- | Go to Step 4 | Go to Diagnostic Aids |
Is the TP sensor voltage less than the specified value? | 0.3 V | Go to Step 5 | Go to Step 6 | |
Does the test lamp illuminate? | -- | Go to Step 7 | Go to Step 9 | |
6 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11 |
|
Important:: The 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 to B+, the other 5.0 volt reference circuits will also have a low or high voltage.
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 8 | |
8 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 |
9 |
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 |
10 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Did you complete the repair? | -- | Go to Step 13 | -- |
11 | Inspect for a poor connection at the PCM connector. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 |
|
Important:: The repalcment PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the repair? | -- | Go to Step 13 | -- | |
13 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
