Circuit Description
The throttle position (TP) sensor 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 3 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 ECM 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.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage
Conditions for Running the DTC
| • | The battery voltage is more than 8 volts. |
| • | The ignition is ON. |
| • | DTC P0122 runs continuously once the above conditions are met. |
Conditions for Setting the DTC
The TP sensor 1 voltage is less than 0.18 volt for less than 1 second.
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 TP 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.
-
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 | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||||
2 |
Is the TP sensor 1 voltage less than the specified value? | 0.2 V | Go to Step 5 | Go to Step 3 | ||||||||
3 |
Did the DTC fail this ignition? | -- | Go to Step 5 | Go to Step 4 | ||||||||
Did the DTC fail this ignition? | -- | Go to Step 14 | Go to Intermittent Conditions | |||||||||
5 |
Is the voltage within the specified range? | 4.8-5.2 V | Go to Step 6 | Go to Step 7 | ||||||||
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 11 | Go to Step 9 | |||||||||
Is the voltage within the specified range? | 4.8-5.2 V | Go to Step 13 | Go to Step 8 | |||||||||
8 |
Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 10 | ||||||||
9 |
Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 12 | ||||||||
10 | 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 16 | Go to Step 12 | ||||||||
11 | 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 16 | Go to Step 14 | ||||||||
12 | Test for an intermittent and for a poor connection at the engine control module (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 16 | Go to Step 15 | ||||||||
13 | Replace the APP sensor. Refer to Accelerator Pedal Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 16 | -- | ||||||||
14 | Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement . Did you complete the replacement? | -- | Go to Step 16 | -- | ||||||||
15 | Replace the ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 16 | -- | ||||||||
16 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 17 | ||||||||
17 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK | ||||||||
