For 1990-2009 cars
Cell 20: 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 contains a potentiometer whose resistance value changes along with the throttle valve position. The powertrain control module (PCM) provides a 5 volt reference voltage to the TP sensor. The PCM reads the voltage across the TP sensor and converts it into the throttle position. The TP sensor resistance decreases as the throttle valve opening increases. When the TP sensor resistance decreases the voltage being monitored at the PCM will increase. And when the TP sensor resistance increases, because the throttle valve opening is decreasing, the voltage being monitored at the PCM will decrease.

### Conditions for Setting the DTC

• | High TP sensor voltage (TP angle is greater than 96%) is indicated at the PCM with the engine running.

• | The above condition is met for at least 5 seconds.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL).

• | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

### Conditions for Clearing the MIL/DTC

• | The MIL turns OFF after three consecutively passing trips without a fault present.

• | A History DTC clears after 40 consecutive warm-up cycles without a fault.

• | Use the scan tool Clear DTC Information function or disconnect the PCM battery feed in order to clear the DTC.

### Diagnostic Aids

A misadjusted TP sensor could cause a DTC P0123 to set. Refer to Throttle Position Sensor Adjustment .

An intermittent malfunction may be caused by a fault in the TP sensor electrical circuit. Inspect the wiring harness and components for any of the following conditions:

• | Backed out terminals.

• | Improper mating of terminals.

• | Broken electrical connector locks.

• | Improperly formed or damaged terminals.

• | Faulty terminal to wire connections.

• | Physical damage to the wiring harness.

• | A broken wire inside the insulation.

• | Corrosion of electrical connections, splices, or terminals.

If a DTC P0123 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

### Test Description

The numbers below refer to the step numbers in the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. The percentage of TP sensor movement should not be greater than 96% when observing the TP sensor parameter from closed throttle position to wide open throttle.

3. A TP sensor is out of specifications and cannot be adjusted should be replaced.

Step | Action | Value(s) | 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, leaving the engine OFF.
2. Install a scan tool.
3. Observe the TP sensor parameter on the scan tool while the accelerator pedal is depressed from the idle position to wide open throttle.

Is the TP sensor percentage at or greater than the specified value?

96%

Go to Step 4

Go to Step 3

3 |

1. Turn ON the ignition, leaving the engine OFF.
2. Clear the scan tool information.
3. Operate the vehicle within the Freeze Frame conditions as noted.

Is the TP sensor percentage greater than the specified value?

96%

Go to Step 4

Go to Diagnostic Aids

4 |

1. Turn ON the ignition, leaving the engine OFF.
2. Disconnect the TP sensor connector.
3. Measure the voltage from the 5 volt reference circuit (harness side), using a DMM.

Is the voltage between the specified value?

4 to 6 volts

Go to Step 5

Go to Step 8

5 | Probe the TP sensor ground circuit at the TP sensor harness connector, using a test light connected to B+. Is the test light ON? | -- | Go to Step 6 | Go to Step 10
6 |

1. Turn OFF the ignition.
2. Reconnect the TP sensor connector.
3. Turn ON the ignition, leaving the engine OFF.
4. Measure the voltage by backprobing the TP sensor signal circuit at the PCM, using a DMM,

Is the TP sensor signal voltage between the specified value?

0.5 to 1.2 volts

Go to Step 12

Go to Step 7

7 |

1. Turn OFF the ignition.
2. Disconnect the PCM.
3. Check for an open circuit or short to voltage on the TP sensor signal circuit
4. Repair any open or short in the TP sensor signal circuit as necessary. Refer to Wiring Repairs in Wiring Sytems.

Was a repair necessary?

--

Go to Step 13

Go to Step 9

8 |

1. Turn OFF the ignition.
2. Disconnect the PCM.
3. Check for an open circuit or short to voltage on the 5 volt reference circuit.
4. Repair any open or short in the 5 volt reference signal circuit as necessary. Refer to Wiring Repairs in Wiring Sytems.

Was a repair necessary?

--

Go to Step 13

Go to Step 12

9 | Check for faulty electrical connections at the TP sensor and repair as necessary. Was a repair necessary? | -- | Go to Step 13 | Go to Step 11
10 | Check for an open TP sensor ground circuit or a faulty ground circuit connection. Repair as necessary. Refer to Wiring Repairs in Wiring Sytems. Was a repair necessary? | -- | Go to Step 13 | Go to Step 12
11 | Adjust or replace the TP sensor. Refer to Throttle Position Sensor Adjustment and Throttle Position Sensor Replacement . Is the action complete? | -- | Go to Step 13 | --
12 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 13 | --
13 |

1. Perform the scan tool DTC Information function and road test the vehicle within the conditions that set the DTC.
2. Check for DTCs.
3. Review the scan tool data. If no DTCs are set, the repair is complete.

Are any DTCs displayed on the scan tool?

--

Go to the Applicable DTC Table

System OK