For 1990-2009 cars

### Circuit Description

The DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage diagnostic monitors the TP sensor signal. The TP sensor is 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 uses the voltage to calculate the percentage of throttle valve opening. The TP sensor resistance decreases as the throttle valve opening increases. When the TP sensor resistance decreases the voltage being monitored by the PCM increases. The TP sensor resistance increases when the throttle valve opening decreases, therefore the voltage being monitored by the PCM will decrease.

### Condition for Running the DTC

The ignition is ON or the engine is running.

### Conditions for Setting the DTC

• | A low voltage TP sensor input is indicated at the PCM.

• | The above condition is present 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.

• | The PCM enters the Failsafe mode and assumes the engine throttle valve angle is 24.5 degrees.

### Conditions for Clearing the MIL/DTC

• | The MIL turns OFF after 3 consecutively passing cycles without a fault present.

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

• | Perform the scan tool clear DTC Information function in order to clear the DTC.

### Diagnostic Aids

On a cold engine the TP sensor may indicate 3 percent or more with the throttle closed at idle. After the engine warms up and the plunger of the fast idle-up valve has retracted, the TP sensor will indicate 0 percent at idle.

If a DTC P0122 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool clear DTC information function. Road test the vehicle while monitoring the DTC P0122 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0122 appears in the Not Ran Since Code Cleared list, the DTC P0122 diagnostic has not yet run. When the DTC P0122 does not appear in the Not Ran Since Code Cleared list, the DTC P0122 diagnostic has run. If the MIL is NOT illuminated, and there is no DTC Status in DTC Information, the DTC P0122 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.

An intermittent malfunction may be caused by a fault in the TP sensor electrical circuit. Inspect the wiring harness and the components for an intermittent condition. Refer to Intermittent Conditions .

If the DTC P0122 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 Diagnostic System Check-Engine Controls 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. This step determines whether the malfunction that caused the DTC P0122 is still present. Driving the vehicle under these conditions will verify whether the fault is present. After performing the scan tool clear DTC information function, the DTC P0122 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If DTC P0122 appears in the Not Ran Since Code Cleared list, the DTC P0122 diagnostic has not yet run. When DTC P0122 does not appear in the Not Ran Since Code Cleared list, the DTC P0122 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P0122 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.

3. When the 5-volt reference is jumpered to the TP input circuit, the scan tool parameter should read 99 percent.

4. When the TP sensor input circuit is jumpered to battery voltage , the scan tool parameter should read 99 percent.

5. This step checks whether the malfunction that caused the DTC P0122 is still present. Driving the vehicle under these conditions will verify whether the fault is present. After performing the scan tool clear DTC information function, the DTC P0122 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0122 appears in the Not Ran Since Code Cleared list, the DTC P0122 diagnostic has not yet run. When the DTC P0122 does not appear in the Not Ran Since Code Cleared list, the DTC P0122 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P0122 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status, in order to determine the outcome of the diagnostic test involved.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 |

1. Start the engine.
2. Run the engine until the engine reaches a normal operating temperature.
3. Turn OFF the ignition.
4. Turn ON the ignition, leaving the engine OFF.
5. Observe the TP sensor parameter on the scan tool while the accelerator pedal is depressed from the idle position to wide open throttle (WOT).

Does the TP sensor percentage steadily increase within the specified range?

0-99%

Go to Step 3

Go to Step 4

3 |

1. Perform the scan tool Clear DTC Information function.
2. Operate the vehicle within the Freeze Frame conditions as specified, or until the DTC P0122 diagnostic has run.

Did DTC P0122 set?

--

Go to Step 4

Go to Diagnostic Aids

4 |

1. Disconnect the TP sensor electrical connector.
2. Jump the 5 volt reference circuit and the TP sensor input circuit together at the TP sensor harness connector.
3. Select the TP sensor parameter on the scan tool.

Does the TP sensor percentage equal the specified value?

99%

Go to Step 9

Go to Step 5

5 |

1. Connect a test lamp between B+ and the TP sensor input circuit at the TP sensor harness connector.
2. Monitor the TP sensor with the scan tool.

Does TP sensor percentage equal the specified value?

99%

Go to Step 6

Go to Step 7

6 |

1. Turn OFF the ignition.
2. Disconnect the PCM electrical connector at the PCM.
3. Check the 5 volt reference circuit for an open or a short.
4. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 12

Go to Step 8

7 |

1. Turn OFF the ignition.
2. Disconnect the PCM electrical connector.
3. Test the TP sensor input circuit for a short to ground.
4. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 12

Go to Step 8

8 |

1. Check the TP sensor circuits for faulty connections at the sensor and at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 12

Go to Step 11

9 |

1. Check the TP sensor circuits for faulty connections at the sensor and at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 12

Go to Step 10

10 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Is the action complete? | -- | Go to Step 12 | --
11 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | Go to Step 12 | --
12 |

1. Use the scan tool in order to clear the DTCs.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 13

Go to Step 2

13 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List | System OK