DTC P0122. Cadillac CTS

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 2003 🢒 CTS - RHD 🢒 Engine 🢒 Engine Controls - 2.6L and 3.2L 🢒 DTC P0122

Circuit Description

The throttle position (TP) sensors 1 is used to determine the throttle plate angle by the engine control module (ECM) for various engine management systems. The TP sensor is a potentiometer type sensor with the following three circuits:

•	A 5-volt reference circuit

•	A low reference circuit

•	A signal circuit

The ECM provides the TP sensor with a 5-volt reference circuit and a low reference circuit. The TP sensor then provides the PCM with a signal voltage proportional to throttle plate movement. The TP sensor 1 signal voltage at closed throttle is low and increases as the throttle is opened. When the ECM detects the TP sensor 1 voltage is less than 0.195 volts, DTC P0122 sets.

Conditions for Running the DTC

•	The battery voltage is more than 10 volts.

•	The ignition is ON.

Conditions for Setting the DTC

The TP sensor 1 voltage is less than 0.195 volt for more than 140 milliseconds.

Action Taken When the DTC Sets

•	The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

•

The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

•	The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

•	A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

•	A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

•	Clear the MIL and the DTC with a scan tool.

Test Description

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

The ECM performs a comparison of the signals from both throttle position sensors during the entire range of operation. If the DTC does not set with the key ON and the accelerator pedal released, actuating the throttle may cause the DTC to set.

This step tests for the proper operation of the TP sensor 1 signal circuit. The ECM supplies a pull up voltage of about 4.8 volts on the signal circuit.

This step is to test the integrity of the low reference circuit through the ECM.

The 5-volt reference for the TP sensors and the accelerator pedal position (APP) sensor 2 are connected inside the ECM. This step is to determine if the APP sensor is affecting the 5-volt reference circuit of the TP sensors.

Step

Action

Values

Yes

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

Turn ON the ignition, with the engine OFF.
Observe the throttle position (TP) sensor 1 voltage with a scan tool.

Is the TP sensor 1 voltage less than the specified value?

0.2 V

Go to Step 5

Go to Step 3

Observe the Freeze Frame/Failure Records for this DTC.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or as close to the Freeze Frame/Failure Records that you observed.

Did the DTC fail this ignition?

Go to Step 5

Go to Step 4

Clear the DTCs with a scan tool.
Slowly depress the accelerator pedal to wide-open throttle (WOT) and then slowly return it to the closed position.
Repeat this action several times.

Did the DTC fail this ignition?

Go to Step 18

Go to Intermittent Conditions

•	Turn OFF the ignition.

•	Disconnect the throttle body harness connector. Refer to Throttle Body Assembly Replacement .

•	Turn ON the ignition, with the engine OFF.

•	Measure the voltage from the 5-volt reference circuit of the TP sensor to a good ground with a DMM.

Is the voltage within the specified range?

4.8-5.2 V

Go to Step 6

Go to Step 10

Measure the voltage from the signal circuit of the TP sensor 1 to a good ground with a DMM.

Is the voltage within the specified range?

4.6-4.9 V

Go to Step 7

Go to Step 12

Turn OFF the ignition for 30 seconds.

Important: It may be necessary to remove the ECM/TCM fuse to allow the ECM to power down.

Allow the engine control module (ECM) to completely power down. This can be verified by the loss of communication on the scan tool.
Measure the resistance from the low reference circuit of the TP sensor to a good ground with the DMM.

Is the resistance less than the specified value?

5ohms

Go to Step 15

Go to Step 8

Test the low reference circuit of the TP sensor 1 for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 20

Go to Step 9

Measure the resistance from the case of the ECM to battery ground.

Is the resistance less than the specified value?

5ohms

Go to Step 16

Go to Step 14

Turn OFF the ignition.
Disconnect the accelerator pedal position (APP) sensor harness connector. Refer to Accelerator Pedal Position Sensor Replacement .
Turn ON the ignition, with the engine OFF.
Measure the voltage from the 5-volt reference circuit of the TP sensor 1 to a good ground with a DMM.

Is the voltage within the specified range?

4.8-5.2 V

Go to Step 17

Go to Step 11

Test the 5-volt reference circuit of the TP sensor for the following conditions:

•	A short to ground

•	High resistance

•	An open circuit

Repair as necessary. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 20

Go to Step 13

Test the signal circuit of the TP sensor 1 for the following conditions:

•	A short to ground

•	A short to the low reference circuit

•	High resistance

•	An open circuit

Repair as necessary. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 20

Go to Step 16

Test the 5-volt reference circuit of the APP sensor 2 for a short to ground. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 20

Go to Step 16

Repair the open or high resistance in the ECM ground circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 20

Test for an intermittent and for a poor connection at the at the TP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 20

Go to Step 18

Test for an intermittent and for a poor connection at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 20

Go to Step 19

Replace the APP sensor. Refer to Accelerator Pedal Position Sensor Replacement .

Did you complete the replacement?

Go to Step 20

Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement .

Did you complete the replacement?

Go to Step 20

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

Go to Step 20

Clear the DTCs with a scan tool.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 21

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK