DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage


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Circuit Description

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

The TP sensor signal voltage should be about 0.6 volt at idle. The TP sensor voltage should increase to above 4.0 volts at wide open throttle (WOT).

When the PCM senses a signal voltage lower than the normal operating range of the sensor, this DTC sets.

Conditions for Running the DTC

The ignition switch is in the ON position or the engine is operating.

Conditions for Setting the DTC

Action Taken When the DTC Sets

Conditions for Clearing the MIL/DTC

Diagnostic Aids

Important

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. If DTC P1639 sets at the same time, this indicates that the 5.0 volt reference circuit is either shorted to a ground or shorted to a voltage. The 5.0 volt reference circuit is internally connected within the PCM.
  1. This step verifies that a malfunction is present.
  1. Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicated the DTC, the information included in the Freeze Frame and/or Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed. For an intermittent condition, refer to Symptoms .
  1. This determines if the short is caused from the Accelerator and Servo Control Module. After repairs are made, reconnect the Accelerator and Servo Control Module and clear any DTCs that set when the Accelerator and Servo Control Module was disconnected.
  1. If the scan tool indicates 5.0 volts, indicates the TP sensor circuits and PCM are OK.
  1. Disconnecting the PCM will allow using the DMM J 39200 to test continuity of the circuits. This will aid in locating an open or shorted circuit.
  1. Disconnecting the PCM will allow using the DMM J 39200 to test continuity of the circuits. This will aid in locating an open or shorted circuit. Refer to Wiring Repairs in Wiring Systems.
  1. Disconnecting the PCM will allow using the DMM J 39200 to test continuity of the circuits. This will aid in locating an open or shorted 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 A Powertrain On Board Diagnostic (OBD) System Check

2

  1. Install the scan tool.
  2. Idle the engine.
  3. Monitor the Diagnostic Trouble Code (DTC) information using the scan tool.

Did DTC P1639 fail this ignition?

--

Go to DTC P1639 5 Volt Reference 2 Circuit

Go to Step 3

3

  1. Turn ON the ignition leaving the engine OFF.
  2. With the throttle closed, monitor the TP sensor display on the scan tool.

Is the TP sensor voltage below the specified value?

0.2V

Go to Step 5

Go to Step 4

4

  1. Turn ON the ignition leaving the engine OFF.
  2. Review the Freeze Frame and/or Failure Records data for this DTC and record the parameters.
  3. Turn OFF the ignition for 15 seconds.
  4. Start the engine.
  5. Operate the vehicle within the conditions required for this diagnostic to run, and as close to the conditions recorded in Freeze Frame/Failure Records as possible. Special operating conditions that you need to meet before the PCM will run this diagnostic, where applicable, are listed in Conditions for Running the DTC.
  6. Select the Diagnostic Trouble Code (DTC) option, the Specific DTC option, then enter the DTC number which was set using the scan tool.

Does the scan tool indicate that this diagnostic failed this ignition?

--

Go to Step 5

Go to Diagnostic Aids

5

Important

After you complete this diagnosis reconnect the Accelerator and Servo Control Module. Also, clear the Accelerator and Servo Control Module DTCs that set when the Accelerator and Servo Control Module was disconnected.

  1. Turn OFF the ignition.
  2. Disconnect the Accelerator and Servo Control Module. Refer to Accelerator and Servo Control Module (ASM) Replacement in Antilock Brake System.
  3. Turn ON the ignition leaving the engine OFF.

Is the TP sensor voltage still below the specified value?

0.2V

Go to Step 6

Go to A Diagnostic System Check in Antilock Brake System

6

  1. Disconnect the TP sensor electrical connector.
  2. Jumper the 5.0 volt reference circuit and the TP signal circuit together at the TP sensor harness connector.
  3. Observe the TP sensor voltage display on the scan tool.

Is the TP sensor voltage above the specified value?

4.7V

Go to Step 12

Go to Step 7

7

  1. Connect the test lamp J 34142-B between B+ and the TP sensor signal circuit at the TP sensor harness connector.
  2. Observe the TP sensor voltage display on the scan tool.

Is the TP sensor voltage above the specified value?

4.7V

Go to Step 8

Go to Step 10

8

  1. Turn OFF the ignition.
  2. Disconnect the PCM C2 connector located on the same side of the manufacturer's logo. Refer to PCM Replacement/Programming .
  3. Test the 5.0 volt reference circuit for an open or short to ground.
  4. If the 5.0 volt reference circuit is open or shorted to ground, repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 9

9

  1. Test the 5.0 volt reference circuit for a poor connection at the PCM. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
  2. If you find a poor connection, repair as necessary. Refer to Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 13

10

  1. Turn OFF the ignition.
  2. Disconnect the PCM connector C2 located on the same side of the manufacturer's logo. Refer to PCM Replacement/Programming .
  3. Test the TP signal circuit for an open, short to ground, or for a short to the sensor ground circuit.
  4. If you find the TP sensor signal circuit is open or shorted to ground, repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 11

11

  1. Test the TP sensor signal circuit for a poor connection at the PCM. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
  2. If you find a poor connection, repair as necessary. Refer to Repairing Connector Terminals 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 TP Sensor Replacement . Is the action complete?

--

Go to Step 14

--

13

Important:

Program the replacement PCM. Refer to PCM Replacement/Programming .

Replace the PCM. Is the action complete?

--

Go to Step 14

--

14

  1. Select the Diagnostic Trouble Code (DTC) option and the Clear DTC Information option using the scan tool.
  2. Idle the engine at the normal operating temperature.
  3. Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text, if applicable.

Does the scan tool indicate that this test ran and passed?

--

Go to Step 15

Go to Step 2

15

Select the Capture Info option and the Review Info using the scan tool. Does the scan tool display any DTCs that you have not diagnosed?

--

Go to the applicable DTC table

System OK