DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage. GMC Truck Sonoma Pickup

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1998 🢒 Sonoma Pickup - 2WD 🢒 DTC 🢒 DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage

Engine Controls Components
MAP, IAT, TPS, And ECT Sensors
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The Powertrain Control Module (PCM) supplies a 5.0 volt reference signal and a ground to the sensor. The TP sensor sends a voltage signal back to the PCM relative to the throttle plate opening. The voltage will vary from approximately 0.35 volt at closed throttle, to over 4.65 volts at wide open throttle (WOT).

Conditions For Setting The DTC

•	The TP sensor reads less than 0.20V for 6.25 seconds.

•	The engine is running.

Action Taken When the DTC Sets

•	The Malfunction Indicator Lamp (MIL) illuminates.

•	The PCM records the operating conditions at the time the diagnostic fails. This information will be stored in The Freeze Frame and Failure Records buffers stores this information.

•	A history DTC is stored.

•	The TP angle will default to 0% when the vehicle speed is less than 2 mph. The TP angle defaults to 10% when the vehicle speed is greater than 2 mph. The scan tool shows the defaulted value.

Conditions for Clearing the MIL/DTC

•	The malfunction indicator lamp (MIL) will turn OFF after 3 consecutive ignition cycles in which the diagnostic runs without a fault.

•	A history DTC will clear after 40 consecutive warm up cycles without a fault.

•	Use a scan tool to clear the DTCs.

Diagnostic Aids

Whenever this DTC cannot be duplicated, use the information included in the Freeze Frame data in order to evaluate the conditions when the DTC set.

A faulty A/C sensor could set a DTC P0122. Disconnect the A/C electrical connector. If the TP reading returns to normal, replace the A/C Refrigerant Sensor.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

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

The TP sensor has an auto zeroing feature. If the voltage reading is between 0.20 V and 0.90 V, the PCM will automatically assume this as closed throttle position (0%).

Simulates a DTC P0123. If the PCM recognizes the high voltage signal, then the PCM and wiring are OK.

This simulates a high voltage signal which will identify an open in the signal circuit.

If additional DTCs are set, check the 5 V reference circuits for a short to ground.

If the test light illuminates while probing the TP signal circuit, then the TP signal circuit is shorted to ground.

Replacement PCMs must be reprogrammed and the crankshaft position system variation procedure must be performed. Refer to the latest Techline information for PCM reprogramming and also refer to the Crankshaft Position System Variation Learn for the Crankshaft Position System Variation Procedure.

DTC P0122 - Throttle Position (TP) Sensor Circuit Low Voltage

Step	Action	Value(s)	Yes	No
1	Was the Powertrain On-Board Diagnostic (OBD) System Check performed?	--	Go to Step 2	Go to Powertrain On Board Diagnostic (OBD) System Check
2	Turn the ignition switch ON, with the engine OFF. Install a scan tool. Is the TP sensor voltage below the specified value?	0.2V	Go to Step 4	Go to Step 3
3	Review the Freeze Frame data and note the parameters. Operate the vehicle within the Freeze Frame conditions and Conditions For Setting The DTC as noted. Is the TP sensor voltage below the specified value?	0.2V	Go to Step 4	Go to Step 12
4	Disconnect the TP sensor electrical connector. Jumper the 5.0 volt reference circuit and the TP sensor signal circuit together at the TP sensor electrical connector. Is the TP sensor voltage greater than the specified value?	4V	Go to Step 10	Go to Step 5
5	Disconnect jumper wire. Connect a test light between B+ and the TP sensor signal circuit at the TP sensor electrical connector. Is the TP sensor voltage greater than the specified value?	4V	Go to Step 6	Go to Step 8
6	Important: The Powertrain Control Module (PCM) uses a single 5.0 volt power supply to supply power to all the engine control components. If one component shorts its 5.0 volt reference circuit to ground or battery voltage, the other 5.0 volt reference circuits will also have a low or high voltage. Check the 5V reference circuit for an open or short to ground and repair as necessary. Was a repair necessary?	--	Go to Step 12	Go to Step 7
7	Check the 5.0V reference circuit for a poor connection at the PCM. Replace the terminal(s) as necessary. Was a repair necessary?	--	Go to Step 12	Go to Step 11
8	Check the TP sensor signal circuit for open, or a short to ground and repair as necessary. Was a repair necessary?	--	Go to Step 12	Go to Step 9
9	Check the TP sensor signal circuit for a poor connection at the PCM and repair as necessary. Is the action complete?	--	Go to Step 12	Go to Step 11
10	Check the connections at the TP sensor. If OK, 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	Using the scan tool, clear the DTCs. Start the engine and idle at normal operating temperature. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text. Does the scan indicate that this diagnostic ran and passed?	--	Go to Step 13	Go to Step 2
13	Check if any additional DTCs are set. Are any DTCs displayed that have not been diagnosed?	--	Go to the Applicable DTC table	System OK