For 1990-2009 cars
Engine Controls Components
Cell 21: Engine Data Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts 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 volt at closed throttle to about 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.

### Conditions for Setting the DTC

• | The engine is running.

• | TP sensor signal voltage is greater than 4.71 volts.

### Action Taken When the DTC Sets

• | The PCM will illuminate the malfunction indicator lamp (MIL) during the first trip in which the diagnostic runs and fails.

• | If equipped with traction control, the PCM will command the EBTCM via the serial data circuit to turn OFF traction control and illuminate the TRACTION OFF lamp.

• | The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail 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 fault.

• | Faulty TP sensor: With the key ON, engine OFF, 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. Refer to TP Sensor Replacement .

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 Chart may isolate the cause of the fault.

### Test Description

The numbers below refer to the step numbers on the Diagnostic Table:

1. Components that share the TP sensor 5 volt reference A circuit include the following devices, TP sensor, MAP sensor, EGR valve.

   Disconnect these components one at a time while observing the TP sensor display on the scan tool. If the reading changes drastically when one of these components is disconnected, replace the component that affected the reading.

1. 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 in Powertrain Control Module (PCM) and Sensors.

#### DTC P0123 TP Sensor Circuit High Voltage

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain ON-Board Diagnostic Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

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

Is TP Sensor above the specified value?

4.71V

Go to Step 4

Go to Step 3

3 |

1. Turn the ignition ON, engine OFF.
2. Review and record scan tool Fail Records data.
3. Operate vehicle within Fail Records conditions as noted.
4. Using a scan tool, monitor Specific DTC info for DTC P0123.

Does scan tool indicate DTC P0123 failed?

--

Go to Step 4

Go to Diagnostic Aids

4 |

1. Disconnect the TP sensor electrical connector.
2. Observe the TP Sensor display on the scan tool.

Is TP Sensor near the specified value?

0.0.0V

Go to Step 5

Go to Step 6

5 | Probe the sensor ground circuit at the TP sensor harness connector with a test lamp connected to battery positive voltage. Is the test lamp ON? | -- | Go to Step 7 | Go to Step 8
6 |

1. Turn the ignition OFF, disconnect the PCM.
2. Turn the ignition ON, check for a short to voltage on the TP sensor signal circuit.
3. If the TP sensor signal circuit is shorted, repair it as necessary. Refer to Wiring Repairs in Wiring Systems.

Was the TP sensor signal circuit shorted?

--

Go to Step 12

Go to Step 11

7 |

1. Turn the ignition ON.
2. Monitor the TP Sensor scan tool display while disconnecting each of the components that share the 5 volt reference A circuit (one at a time).
3. If the TP Sensor scan tool display changes, replace the component that caused the display to change when disconnected.

Does disconnecting any of these components cause the TP Sensor display to change?

--

Go to Step 12

Go to Step 8

8 |

1. Turn the ignition OFF, disconnect the PCM.
2. Turn the ignition ON, engine OFF.
3. Check for a short to voltage on the 5 volt reference A circuit.
4. If the 5 volt reference A circuit is shorted, repair it as necessary. Refer to Wiring Repairs in Wiring Systems.

Was the 5 volt reference A circuit shorted?

--

Go to Step 12

Go to Step 9

9 | Check for poor electrical connections at the TP sensor and replace terminals if necessary or open sensor ground circuit. Refer to Wiring Repairs in Wiring Systems. Did any terminals or ground circuit require repair? | -- | Go to Step 12 | Go to Step 10
10 | Replace the TP sensor. Refer to TP Sensor Replacement . Is the action complete? | -- | Go to Step 12 | --
11 | Replace the PCM. Important : Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | Go to Step 12 | --
12 |

1. Review and record scan tool Fail Records data.
2. Clear DTCs.
3. Operate vehicle within Fail Records conditions as noted.
4. Using a scan tool, monitor Specific DTC info for DTC P0123.

Does scan tool indicate DTC P0123 failed?

--

Go to Step 2

System OK