Circuit Description
The throttle position (TP) sensors 1 and 2 are located within the throttle body assembly. The TP sensors share a common 5-volt reference circuit and a common low reference circuit. The 5-volt reference circuit is also shared with accelerator pedal position (APP) sensor 2. The 5-volt reference voltage is supplied on 2 separate engine control module (ECM) terminals, but the terminals are connected internally to the same voltage supply. Each TP sensor has an individual signal circuit, which provides the ECM with a signal voltage proportional to the throttle plate movement. When the throttle plate is in the closed position, the TP sensor 1 signal voltage is near the low reference and increases as the throttle plate is opened. TP sensor 2 signal voltage at closed throttle is near the 5-volt reference and decreases as the throttle plate is opened. If the ECM detects the TP sensor 1 signal voltage is less than 0.98 volts, DTC P0122 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0122 Throttle Position (TP) Sensor 1 Circuit Low Voltage
Conditions for Running the DTC
| • | The battery voltage is more than 10 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 0.98 volts for more than 60 milliseconds.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records. |
| • | The control module commands the TAC system to operate in the Reduced Engine Power mode. |
| • | A message center or an indicator displays Reduced Engine Power. |
| • | Under certain conditions the control module commands the engine OFF. |
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.
-
The 5-volt reference for the TP sensors and the 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 | Value | 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 | ||||||||
6 |
Is the voltage within the specified range? | 4.8-5.2 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 | Test the 5-volt reference circuit of the TP sensors for the following conditions:
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 throttle body. 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. More than 1 TAC system-related DTC may set. This is due to the many redundant tests ran continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Be aware of this when reviewing the Capture Info. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK | ||||||||
