Circuit Description
The Throttle Position (TP) sensor circuit provides a voltage signal that changes relative to throttle blade angle. The signal voltage will vary from below 1 volt at closed throttle to above 4 volts at Wide Open Throttle (WOT). The TP signal is one of the most important inputs used by the PCM for fuel control and most of the PCM-controlled outputs. DTC P0123 will set when the PCM detects an excessively high signal voltage on the throttle position sensor signal circuit.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
| • | TP sensor signal voltage is greater than 4.9 volts. |
| • | Above conditions are present for longer than 5 seconds. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) during the first trip in which the diagnostic test has been run and failed. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed. |
| • | The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool. |
Diagnostic Aids
Check for the following conditions:
| • | Poor connection at PCM. |
| Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. |
| • | Damaged harness. |
| Inspect the wiring harness for damage. If the harness appears to be OK, observe the TP sensor display on the scan tool while moving connectors and wiring harnesses related to the TP sensor. A change in the display will indicate the location of the malfunction. |
| • | Malfunctioning TP sensor. |
| With the key ON, engine not running, observe the TP sensor display on the scan tool while slowly depressing the accelerator to wide open throttle. If a voltage over 4.71 volts is seen at any point in normal accelerator travel, replace the TP sensor. |
If DTC P0123 cannot be duplicated, the information included in the Fail Records data can be useful in determining vehicle mileage since the DTC was last set. If it is determined that the DTC occurs intermittently, performing the DTC P1121 Diagnostic Table may isolate the cause of the malfunction.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain OBD System Check performed? | -- | ||
2 |
Is TP Sensor above the specified value? | 4.9V | ||
3 |
Does scan tool indicate DTC P0123 failed? | -- | Go to Diagnostic Aids | |
4 |
Is the TP Sensor Voltage near the specified value? | 0.0V | ||
5 | Probe the TP sensor ground circuit at the TP sensor harness connector with a test light connected to B+. Is the test light on? | -- | ||
6 | Check for a Short to voltage on the TP signal circuit and repair if necessary. Refer to Wiring Repairs in Wiring Systems. Was a repair necesssary? | -- | ||
7 | Check for a poor connection in the TP sensor ground circuit at the PCM and replace termainals if necessary. Refer to Repairing Connector Terminals in Wiring Systems. Was a repair necessary? | -- | ||
8 | Check for an open in the sensor ground circuit and repair if necessary. Refer to Wiring Repairs in Wiring Systems. Was a repair necessary? | -- | ||
9 | Check for a poor connection at the sensor harness connector and replace terminals if necessary. Refer to Repairing Connector Terminals in Wiring Systems. Was a repair necessary? | -- | ||
10 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Is the action complete? | -- | -- | |
|
Important: : Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | -- | ||
12 |
Does scan tool indicate DTC P0123 failed? | -- | System OK |
