DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage

TechInfo · Joined: 26 Oct 2004 Posts: 2989

DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage

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 near 0.6 volts 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

The TP sensor signal voltage is less than 0.2 volts.
The above conditions present for 10.0 seconds.

Action Taken When the DTC Sets

The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Use a scan tool in order to clear the MIL and the DTC.

Diagnostic Aids

Important

Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion into the PCM.
For any test that requires probing the PCM or component harness connectors, use the Connector Test Adapter Kit . Using this kit prevents any damage to the harness connector terminals. Refer to Using Connector Test Adapters in Wiring Systems.

The following may cause an intermittent:

Mis-routed harness
Rubbed through wire insulation
Broken wire inside the insulation

The PCM 5.0 volt reference circuits are internally connected within the PCM. If all the TP sensor circuits are OK, inspect the MAP sensor and EGR valve for malfunctions.
If it is determined that the DTC occurs intermittently, performing the DTC P1122 diagnostic table may isolate the cause of the fault.
Using the Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate 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 the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This isolates when the DTC failed.
For an intermittent, refer to Symptoms .

Test Description

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

If DTC P1639 sets at the same time, this indicates that the 5 volt reference circuit is either shorted to ground or shorted to a voltage. The 5 volt reference circuit is internally connected within the PCM.

This step verifies that a malfunction is present.

Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate 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.

This determines if the short is caused from the Accelerator and Servo Control Module (ASM). After repairs are made, reconnect the Accelerator and Servo Control Module (ASM) and clear any DTCs that set when the Accelerator and Servo Control Module (ASM) was disconnected.

If the scan tool indicates 5 volts, indicates the TP sensor circuits and PCM are OK.

Disconnecting the PCM will allow using the DMM 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 Powertrain On Board Diagnostic (OBD) System Check
2	Install the scan tool. Idle the engine. 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	Turn ON the ignition leaving the engine OFF. 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	Turn ON the ignition leaving the engine OFF. Review the Freeze Frame and/or Failure Records data for this DTC and record the parameters. Turn OFF the ignition for 15 seconds. Start the engine. 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. 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 (ASM). Also, clear any ASM DTCs that may have set when the ASM was disconnected. Turn OFF the ignition. Disconnect the ASM. Refer to Accelerator and Servo Control Module (ASM) Replacement in Antilock Brake System. Turn ON the ignition. Is the TP sensor voltage still below the specified value?	0.2 V	Go to Step 6	Go to Diagnostic System Check - ABS in Antilock Brake System.
6	Disconnect the TP sensor electrical connector. Jumper the 5 volt reference circuit and the TP signal circuit together at the TP sensor harness connector. Observe the TP sensor voltage display on the scan tool. Is the TP sensor voltage above the specified value?	4.7 V	Go to Step 12	Go to Step 7
7	Connect the test lamp between B+ and the TP sensor signal circuit at the TP sensor harness connector. Observe the TP sensor voltage display on the scan tool. Is the TP sensor voltage above the specified value?	4.7 V	Go to Step 8	Go to Step 10
8	Turn OFF the ignition. Disconnect the PCM connector C1 located on the same side of the manufacturer's logo. Refer to PCM Replacement/Programming . Test the 5 volt reference circuit for an open or short to ground. If the 5 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	Test the 5 volt reference circuit for a poor connection at the PCM. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems. If you find a poor connection repair the terminal 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	Turn OFF the ignition. Disconnect the PCM connector C2 located on the opposite side of the manufacturer's logo. Test the signal circuit for an open, short to ground, or for a short to the sensor ground circuit. If you find the 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	Test the sensor signal circuit for a poor connection at the PCM. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems. If you find a poor connection repair the terminal 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 Throttle Position (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	Select the Diagnostic Trouble Code (DTC) option and the Clear DTC Information option using the scan tool. Idle the engine at the normal operating temperature. Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool. 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