For 1990-2009 cars
Engine Controls Components
PCM 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 less than 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. The PCM monitors throttle position and compares actual throttle position from the TP sensor to a predicted TP value calculated from engine speed. If the PCM detects an excessively low TP sensor signal voltage, DTC P0122 will be set.

### Conditions for Setting the DTC

• | The ignition is ON.

• | TP sensor signal voltage is less than 0.16 volt.

• | 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 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 throttle position 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.

If DTC P0122 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 P1122 Diagnostic Chart may isolate the cause of the malfunction.

### Test Description

Number(s) below refer to the Step number(s) on the Diagnostic Table:

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 PCM Replacement and Programming Procedures in Powertrain Control Module (PCM) and Sensors.

#### DTC P0122 - TP Sensor Circuit Low Voltage

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

1. Turn ON the ignition switch, engine not running.
2. With the throttle closed, observe the TP Sensor display on the scan tool.

Is the TP Sensor voltage less than the specified value?

0.16V

Go to Step 4

Go to Step 3

3 |

1. Review and record scan tool Fail Records data.
2. Operate the vehicle within Fail Records conditions.
3. Using a scan tool, monitor Specific DTC info for DTC P0122.

Does the scan tool indicate DTC P0122 failed this ign?

--

Go to Step 4

Go to Diagnostic Aids

4 |

1. Disconnect the TP sensor electrical connector.
2. Jumper the 5 volt reference A circuit and the TP signal together at the TP sensor harness connector.
3. Observe the TP Sensor display on the scan tool.

Is TP Sensor at the specified value?

5V

Go to Step 10

Go to Step 5

5 |

1. Connect a test light between B+ and the TP sensor signal circuit at the TP sensor harness connector
2. Observe the TP Sensor display on the scan tool.

Is TP Sensor at the specified value?

5V

Go to Step 6

Go to Step 8

6 |

1. Turn OFF the ignition switch.
2. Disconnect the PCM.
3. Check the 5 volt reference A circuit for an open or short to ground.
4. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 13

Go to Step 7

7 |

1. Check the 5 volt reference A circuit for a poor connection at the PCM.
2. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 13

Go to Step 12

8 |

1. Turn OFF the ignition switch.
2. Disconnect the PCM.
3. Check for the following conditions:

• | TP signal circuit open.

• | TP signal circuit shorted to ground.

• | TP signal circuit shorted to the sensor ground circuit.

• | 5 volt reference A circuit shorted to ground.

• | 5 volt reference A circuit shorted to the sensor ground circuit.

4. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 13

Go to Step 9

9 |

1. Check the TP sensor signal circuit for a poor connection at the PCM.
2. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 13

Go to Step 12

10 |

1. Check the TP sensor signal circuit for a poor connection at the TP sensor.
2. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 13

Go to Step 11

11 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Is action complete? | -- | Go to Step 13 | --
12 | Replace the PCM. Important: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is action complete? | -- | Go to Step 13 | --
13 |

1. Review and record scan tool Fail Records data.
2. Clear DTCs
3. Operate the vehicle within Fail Records conditions.
4. Using a scan tool, monitor Specific DTC info for DTC P0122.

Does the scan tool indicate DTC P0122 failed?

--

Go to Step 4

System OK