DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage. Pontiac Grand Prix 1999

For 1990-2009 cars only

Makes 🢒 Pontiac 🢒 1999 🢒 Grand Prix 🢒 DTC 🢒 DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage

Engine Controls Components
OBD II Symbol Description Notice
Engine Controls Component Views
Cell 21: Engine Data Sensors-A/C Refrig Press, TP, MAP, ECT, IAT
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The Throttle Position (TP) sensor circuit provides a voltage signal that changes relative to throttle blade angle. The signal voltage will vary from less than 1 volt at closed throttle to about 4 volts at Wide Open Throttle (WOT). The TP signal is one of the most important inputs used by the PCM for fuel control and most of the PCM-controlled outputs. The PCM monitors throttle position and compares actual throttle position from the TP sensor to a predicted TP value calculated from engine speed. If the PCM detects an excessively low TP sensor signal voltage, DTC P0122 will be set.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

•	TP sensor signal voltage is less than 0.1 volt.

•	Above conditions are present for greater than 10 second.

Action Taken When the DTC Sets

•	The PCM will illuminate the MIL during the first trip in which the diagnostic test has been run and failed.

•	The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data.

Conditions for Clearing the MIL/DTC

•	The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed.

•	The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

•	The DTC can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed.

Diagnostic Aids

Check for the following conditions:

•	Poor connection at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection

•	Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the throttle position display on the scan tool while moving connectors and wiring harnesses related to the TP sensor. A change in the display will indicate the location of the malfunction.

If DTC P0122 cannot be duplicated, the information included in the Fail Records data can be useful in determining vehicle mileage since the DTC was last set. If it is determined that the DTC occurs intermittently, performing the DTC P1122 Diagnostic table may isolate the cause of the malfunction.

Test Description

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

This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed. Refer to PCM Replacement and Programming Procedures in Powertrain Control Module (PCM) and Sensors.

DTC P0122 - 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 ON the ignition switch, engine not running. With the throttle closed, observe the TP Sensor display on the scan tool. Is TP Sensor display less than the specified value?	0.16V	Go to Step 4	Go to Step 3
3	Turn ON the ignition switch. Review and record scan tool Fail Records data. Operate the vehicle within Fail Records conditions as noted. Using a scan tool, monitor Specific DTC info for DTC P0122. Does the scan tool indicate DTC P0122 failed?	--	Go to Step 4	Go to Diagnostic Aids
4	Disconnect the TP sensor electrical connector. Jumper the 5 volt reference A circuit and the TP signal together at the TP sensor harness connector. Observe the TP Sensor display on the scan tool. Is TP Sensor at the specified value?	5V	Go to Step 11	Go to Step 5
5	Connect a test light between B+ and the TP sensor signal circuit at the TP sensor harness connector Observe the TP Sensor display on the scan tool. Is TP Sensor at the specified value?	5V	Go to Step 6	Go to Step 8
6	Turn OFF the ignition switch. Disconnect the PCM. Check the 5 volt reference A circuit for an open or short to ground. If the 5 volt reference A circuit is open or shorted to ground, repair it as necessary. Refer to Wiring Repairs . Was a problem found?	--	Go to Step 14	Go to Step 7
7	Check the 5 volt reference A circuit for a poor connection at the PCM. If a problem is found repair as necessary. Refer to Wiring Repairs . Was a problem found?	--	Go to Step 14	Go to Step 13
8	Turn OFF the ignition switch. Disconnect the PCM. Check the 5 volt reference A circuit for a short to ground or for a short to the sensor ground circuit. If a problem is found, repair as necessary. Refer to Wiring Repairs . Was a problem found?	--	Go to Step 14	Go to Step 9
9	Turn OFF the ignition switch. Disconnect the PCM. Check the TP signal circuit for an open, short to ground, or short to the sensor ground circuit. If the TP sensor signal circuit is open or shorted to ground, repair it as necessary. Refer to Wiring Repairs . Was a problem found?	--	Go to Step 14	Go to Step 10
10	Check the TP sensor signal circuit for a poor connection at the PCM If a problem is found, repair as necessary. Refer to Wiring Repairs . Was a problem found?	--	Go to Step 14	Go to Step 13
11	Check the TP sensor signal circuit for a poor connection at the TP sensor. If a problem is found, replace terminal. Refer to Wiring Repairs . Was a problem found?	--	Go to Step 14	Go to Step 12
12	Replace the TP sensor. Refer to Throttle Position Sensor Replacement Is action complete?	--	Go to Step 14	--
13	Important: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming Replace the PCM. Is action complete?	--	Go to Step 14	--
14	Review and record scan tool Fail Records data. Clear DTCs Operate the vehicle within Fail Records conditions as noted. Using a scan tool, monitor Specific DTC info for DTC P0122. Does the scan tool indicate DTC P0122 failed?	--	Go to Step 4	System OK