For 1990-2009 cars
Engine Controls Components
Engine Data Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### 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 1.0 volts at Closed Throttle to above 4.0 volts at Wide Open Throttle (WOT). DTC P0123 will set when the powertrain control module (PCM) detects an excessively high signal voltage on the TP sensor signal circuit.

### Conditions for Running the DTC

Ignition is ON.

### Conditions for Setting the DTC

• | TP sensor signal voltage is more than 4.9 volts.

• | The above conditions are present for longer than 1 second.

### Action Taken When the DTC Sets

• | The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive 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/Failure Records data.

### Conditions for Clearing the MIL/DTC

• | The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has 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 a scan tool.

### Diagnostic Aids

Inspect for the following conditions:

• | High voltage condition on the TP 5 volt reference circuit

• | Short to voltage on the TP sensor signal circuit

• | Open or high resistance on the TP sensor ground circuit

• | A malfunctioning TP sensor

Many situations may lead to an intermittent condition. Perform each inspection or test as directed.

Important: : Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

• | Loose terminal connection

- | Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair.

- | Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair.

• | Damaged harness--Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair.

• | Inspect the powertrain control module (PCM) and the engine grounds for clean and secure connections. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair.

If the condition is determined to be intermittent, reviewing the Snapshot or Freeze Frame/Failure Records may be useful in determining when the DTC or condition was identified.

### Test Description

The numbers below refer to the step numbers on the diagnostic table:

1. The malfuntioning components that share the TP sensor 5-volt reference circuit could cause a high voltage condition on this circuit.

   Disconnect these components one at a time while observing the DMM. If the reading changes drastically when one of these components is disconnected, replace the component that affected the reading.

2. 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.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Turn ON the ignition .
2. With the throttle closed, observe the TP Sensor display on the scan tool.

Is TP sensor more than the specified value?

4.9V

Go to Step 4

Go to Step 3

3 |

1. Review the Freeze Frame and/or Failure records data for this DTC.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or as close to the Freeze Frame and/or Failure records that you observed.

Does the DTC reset?

--

Go to Step 4

Go to Diagnostic Aids

4 |

1. Turn OFF the ignition.
2. Disconnect the TP sensor.
3. Turn ON the ignition, with the engine OFF.
4. With a scan tool, observe the TP voltage parameter.

Does the scan tool indicate that the TP voltage parameter is equal to the specified value?

0.0V

Go to Step 5

Go to Step 8

5 | Using a DMM, measure the voltage between the 5 volt reference circuit of the TP sensor and a known good ground. Does the voltage measure equal to the specified value? | 5.0V | Go to Step 6 | Go to Step 9
6 | Connect a test lamp between the ground circuit of the TP sensor and battery positive voltage. Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 7
7 |

1. Turn OFF the ignition.
2. Disconnect the PCM.
3. Test the ground 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 15

Go to Step 12

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 15 | Go to Step 14
9 | Test all 5 volt reference A 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 15 | Go to Step 10
10 |

1. Connect a DMM between the TP sensor 5-volt reference circuit and the TP sensor ground circuit.
2. Observe voltage while disconnecting all sensors, one at a time, which use a 5-volt reference signal. A change in voltage indicates the faulty sensor.
3. Replace the sensors as necessary Refer to Throttle Position Sensor Replacement .

Did you find and correct the condition?

--

Go to Step 15

Go to Step 14

11 | Inspect for poor connections at the harness connector of the TP sensor. 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 15 | Go to Step 13
12 | Inspect for poor connections at the harness connector of the PCM. 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 15 | Go to Step 14
13 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 15 | --
14 | Important : The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | Go to Step 15 | --
15 |

1. Use the scan tool in order to clear the DTCs.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

System OK

Go to Step 2