Circuit Description
The engine control module (ECM) supplies a 5-volt reference voltage signal and a ground to the throttle position (TP) sensor. The TP sensor sends a voltage signal back to the ECM relative to the throttle plate opening. The voltage signal will vary from approximately 0.33 volts at closed throttle, to over 4.3 volts at wide open throttle (WOT).
The TP signal is used by the ECM for fuel control and for most of the ECM controlled outputs. The TP signal is one of the most important inputs used by the ECM for fuel control and most of the ECM controlled outputs.
Conditions for Setting the DTC
The TP sensor voltage indicates a throttle voltage less than 0.14 volts.
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate. |
| • | The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers. |
| • | A history DTC is stored. |
| • | The TP angle will default to 0 percent when the vehicle speed is less than 3 km/h (2 mph) and 10 percent when the vehicle speed is greater than 3 km/h (2 mph). The scan tool will not display the default value. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after 4 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. |
| • | DTCs can be cleared by using the scan tool. |
| • | Disconnect the ECM battery feed for more than 10 seconds. |
Diagnostic Aids
If the DTC P0122 cannot be duplicated, the information included in the Freeze Frame data can be useful. Use scan tool information data to determine the status of the DTC. If the DTC occurs intermittently, using the diagnostic table may help isolate the problem.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
The On-Board Diagnostic 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 on the scan tool for later reference.
-
The TP sensor has an auto zeroing feature. If the voltage reading is between 0.2-0.9 volts, the ECM will assume the TP sensor is at a closed throttle position, 0 percent.
-
This step simulates a high voltage signal which will identify an open in the signal circuit.
-
If additional DTCs are set, inspect the 5-volt 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.
-
The replacement ECM must be reprogrammed. Refer to the latest Techline procedure for ECM reprogramming.
-
If no faults have been found at this point and no additional DTCs were set, refer to Diagnostic Aids for additional inspections and information.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Perform an On-Board Diagnostic System Check. Was the check performed? | -- | Go to Step 2 | ||
Is the throttle position (TP) sensor voltage less than the specified value? | 0.2 V | Go to Step 4 | Go to Step 3 | |
3 |
Is the TP sensor voltage less than the specified value? | 0.2 V | Go to Step 4 | Go to Step 12 |
4 |
Is the TP sensor voltage greater than the specified value? | 4 V | Go to Step 10 | Go to Step 5 |
Connect a test light between B+ and the TP sensor signal circuit terminal 3. Is the TP sensor voltage greater than the specified value? | 4 V | Go to Step 6 | Go to Step 8 | |
Inspect the TP sensor 5-volt reference circuit for an open or short to ground and repair as needed. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 7 | |
7 | Inspect the 5-volt reference circuit for a poor connection at terminal A15 of the engine control module (ECM) and repair as needed. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 |
Inspect the TP sensor signal circuit between terminal 3 of the TP sensor and terminal A7 of the ECM for an open or a short to ground and repair as needed. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 | |
9 | Inspect the TP sensor signal circuit, terminal A7 of the ECM for a poor connection and repair as needed. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 |
10 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement Did you complete the replacement? | -- | Go to Step 12 | -- |
Did you complete the replacement? | -- | Go to Step 12 | -- | |
12 |
Does the scan tool indicate that this diagnostic has run and passed? | -- | Go to Step 13 | Go to Step 2 |
Are any DTCs displayed that have not been diagnosed? | -- | Go to applicable DTC table | System OK |
