For 1990-2009 cars
Engine Controls Components
Cell 20: Engine Data Sensors - TP, ECT, IAT and Fuel Tank
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The Throttle Position (TP) sensor is a potentiometer. The TP sensor is mounted on the side of the throttle body. The TP sensor provides a voltage signal that changes relative to the throttle blade angle. This signal voltage is one of the most important inputs that is used by the ECM. The TP sensor has a 5.0 volt reference, a ground and a signal circuit. The signal circuit is pulled up to 5.0 volts within the ECM.

When the ECM senses a signal voltage outside of the normal operating range of the sensor, this DTC will set.

### Conditions for Running the DTC

The engine speed is greater than 400 RPM.

### Conditions for Setting the DTC

• | The throttle angle is greater than 96% OR less than 3.9%.

• | The above conditions are met for at least 50 milliseconds

| OR

• | While cranking the engine, the above conditions are met for at least 2 seconds.

### Action Taken When the DTC Sets

• | The ECM illuminates the Malfunction Indicator Lamp (MIL) and records the operating conditions in the Freeze Frame on the second consecutive drive trip that the diagnostic runs and fails.

• | The ECM informs the TCM of this condition and the TCM enters the Default Mode. The TCM will also request the ECM to illuminate the MIL and will set DTC P1700.

### Conditions for Clearing the MIL/DTC

• | The ECM turns OFF the MIL after three consecutive drive trips that the diagnostic runs and passes.

• | A History DTC clears after forty consecutive warm-up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic.

• | The ECM battery voltage is interrupted.

• | The scan tool clears the MIL/DTC.

### Diagnostic Aids

Use the Connector Test Adapter Kit J 35616 for any test that requires probing the ECM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals.

Check the following conditions:

• | Poor connections at the ECM or at the component. Inspect the harness connectors for the following conditions:

- | Backed out terminals

- | Improper mating

- | Broken locks

- | Improperly formed or damaged terminals

- | Poor terminal to wire connection

- | Refer to Engine Control Module Diagnosis , Checking Terminal Contact, for the proper procedure.

• | Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving the related connectors and the wiring harnesses. A change in the display may help in order to locate the fault.

| If the sensor signal is only affected when the harness is moved at a component, and there is no problem with the harness or the connections, the component may be damaged.

| Refer to Symptoms for the Intermittents.

• | If other DTCs are set that share the same 5.0 volt reference circuit, check the entire circuit up to any other components. Check for any shorts to ground or power. If the DTCs are set that share the same ground circuit, check the point where the circuits ground to the chassis or to the engine block.

### Test Description

The number(s) below refer to the step numbers on the diagnostic table:

1. Make sure that all of the test connections are good in order to prevent an inaccurate sweep test of the sensor. Use the jumper wires with the proper mating terminals for the sensor and the harness connector.

#### DTC P0120 - Throttle Position (TP) Sensor Circuit

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 with the engine off.
2. Monitor the TP Sensor with the scan tool.

Is the voltage within the specified range?

0.3-0.9 V

Go to Step 3

Go to Step 6

3 | Fully depress the accelerator pedal. Is the voltage within the specified range? | 4.0-5.0 V | Go to Step 4 | Go to Step 6
4 |

1. Turn on the ignition with the engine off.
2. Move the TP sensor electrical connector, the harness and the ECM connectors (by hand only) while observing the scan tool display.

Is the TP value affected by moving the harness or connectors?

--

Go to Step 17

Go to Step 5

5 |

1. Turn off the ignition.
2. Disconnect the TP sensor.
3. Reconnect the TP sensor 5 volt reference circuit and the ground circuit using 2 jumper wires having the appropriate mating terminals between the harness connector and the sensor.
4. Connect the DVM J 39200 between the battery ground and the TP sensor signal terminal in the TP sensor.
5. Turn on the ignition with the engine off.
6. Slowly move the throttle shaft to WOT and then return the throttle shaft to the closed throttle while observing the voltage display on the DVM.
7. The voltage should increase smoothly to WOT and decrease smoothly as the throttle is closed without any voltage spikes or drop outs that are noted on the DVM.

Was a problem found?

--

Go to Step 26

Refer to Diagnostic Aids

6 |

1. Disconnect the TP sensor harness connector.
2. Measure the voltage from the TP sensor signal circuit in the TP sensor harness connector to battery ground with the DVM J 39200 .

Is the voltage within the specified range?

4.7-5.3 V

Go to Step 10

Go to Step 7

7 |

1. Turn off the ignition.
2. Leave the TP sensor disconnected.
3. Disconnect the ECM
4. Turn on the ignition.
5. Measure voltage from the TP sensor signal circuit in the TP sensor harness connector to battery ground with the DVM J 39200 .

Is there any voltage present?

--

Go to Step 21

Go to Step 8

8 | Check the harness for continuity of the TP sensor signal circuit with DVM J 39200 . Is continuity indicated? | -- | Go to Step 9 | Go to Step 22
9 | Check the harness for continuity between the TP sensor signal circuit and battery ground with the DVM J 39200 . Is continuity indicated? | -- | Go to Step 23 | Go to Step 27
10 | Use the DVM J 39200 in order to measure the voltage from the TP sensor 5.0 volt reference circuit in the TP sensor harness connector to battery ground. Is the voltage within the specified range? | 4.7-5.3 V | Go to Step 14 | Go to Step 11
11 |

1. Turn off the ignition.
2. Leave the TP sensor disconnected.
3. Disconnect the ECM.
4. Turn on the ignition.
5. Use the DVM J 39200 in order to measure the voltage from the TP sensor 5.0 volt reference circuit in the TP sensor harness connector to battery ground.

Is there any voltage present?

--

Go to Step 18

Go to Step 12

12 | Check the harness for continuity of the TP sensor 5.0 volt reference circuit with the DVM J 39200 . Is continuity indicated? | -- | Go to Step 13 | Go to Step 19
13 | Check the harness for continuity between the TP sensor 5.0 volt reference circuit and battery ground with the DVM J 39200 . Is continuity indicated? | -- | Go to Step 20 | Go to Step 27
14 |

1. Turn off the ignition.
2. Probe the TP sensor ground circuit in the TP sensor harness connector with the test light J 34142-B connected to B+.

Does the test light illuminate?

--

Go to Step 16

Go to Step 15

15 |

1. Leave the TP sensor disconnected.
2. Disconnect the ECM.
3. Check the harness for continuity of the TP sensor ground circuit with the DVM J 39200 .

Is continuity indicated?

--

Go to Step 27

Go to Step 24

16 |

1. Turn on the ignition on with the engine off.
2. Monitor the TP sensor Voltage with the scan tool.
3. With a fused jumper wire, jumper the TP sensor signal circuit to the TP sensor ground circuit in the TP sensor harness connector.

Does the scan tool indicate the specified voltage?

0.5 V

Go to Step 25

Go to Step 28

17 | Repair the harness/connections as necessary. Refer to Symptoms Is the action complete? | -- | Go to Step 29 | --
18 | Repair the short to voltage in the 5.0 volt reference circuit. Is the action complete? | -- | Go to Step 29 | --
19 | Repair the open/high resistance in the 5.0 volt reference circuit. Is the action complete? | -- | Go to Step 29 | --
20 | Repair the short to ground in the 5 volt reference circuit. Is the action complete? | -- | Go to Step 29 | --
21 | Repair the signal circuit that is shorted to voltage. Is the action complete? | -- | Go to Step 29 | --
22 | Repair the open/high resistance in the signal circuit. Is the action complete? | -- | Go to Step 29 | --
23 | Repair the short to ground in the signal circuit. Is the action complete? | -- | Go to Step 29 | --
24 | Repair the open/high resistance in the ground circuit. Is the action complete? | -- | Go to Step 29 | --
25 | Check for a poor connection or poor terminal tension at the TP sensor harness connector. Refer to Electrical Diagnosis in Engine Electrical, and Troubleshooting Procedures for the proper procedure. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis .

Was a problem found and corrected.

--

Go to Step 29

Go to Step 26

26 | Replace the TP sensor. Is the action complete? | -- | Go to Step 29 | --
27 | Check for a poor connection of poor terminal tension at the ECM harness connector. Refer to Electrical Diagnosis in Engine Electrical, and Troubleshooting Procedures for the proper procedure. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis .

Was a problem found and corrected?

--

Go to Step 29

Go to Step 28

28 | Important: This vehicle is equipped with a Theft Deterrent System which interfaces with the Engine Control Module (ECM). Program the new ECM with the frequency code of the theft deterrent module that is currently on the vehicle. Replace the ECM. Refer to Engine Control Module Replacement/Programming .

Is the action complete?

--

Go to Step 29

--

29 |

1. Clear the DTCs with the scan tool.
2. Turn off the ignition for 15 seconds.
3. Start the engine.
4. Operate the vehicle within the conditions that are required for this diagnostic to run. Refer to Conditions for Running the DTC.
5. Check for any DTCs.

Is this DTC set?

--

Go to Step 2

Go to Step 30

30 | Were there any additional DTCs noted during the Powertrain OBD System Check that have not been diagnosed? | -- | Go to the applicable DTC table | The System is OK