For 1990-2009 cars
Engine Controls Components
Engine Controls Schematics
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 PCM detects an excessively high signal voltage on the throttle position sensor signal circuit.

### Conditions for Running the DTC

The ignition is ON.

### Conditions for Setting the DTC

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

• | The above condition is 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

• | The following components share the TP sensor 5 Volt Reference A circuit:

- | The EGR valve

- | The MAP sensor

• | Test all 5 volt reference A circuits and connected components for a short to voltage:

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. Tests the components that share the TP sensor 5 Volt Reference A circuit which include the EGR valve, the MAP sensor and the TP sensor.

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.

#### DTC P0123 - TP Sensor Circuit High Voltage

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. Turn ON the ignition.
2. Review and record scan tool Failure Records data.
3. Operate vehicle within Failure Records conditions as noted.
4. Use a scan tool in order to monitor Specific DTC info for DTC P0123.

Does scan tool indicate DTC P0123 failed?

--

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 | Use a DMM in order to 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 10 | 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 14

Go to Step 11

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 14 | Go to Step 13
9 | Test all 5 volt reference A circuits and connected components 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 14 | Go to Step 13
10 | 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 14 | Go to Step 12
11 | 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 14 | Go to Step 13
12 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 14 | --
13 | Important: : Replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | Go to Step 14 | --
14 |

1. Review and record scan tool Failure Records data.
2. Clear DTCs
3. Operate the vehicle within Failure Records conditions.
4. Use a scan tool in order to monitor Specific DTC info for DTC P0123.

Does scan tool indicate DTC P0123 failed?

--

Go to Step 4

System OK