Circuit Description
The throttle body assembly contains a throttle position (TP) sensor. The TP sensor is mounted within the throttle body assembly and is not serviceable. The TP sensor is a potentiometer which provides a signal voltage that changes relative to the throttle blade angle. The engine control module (ECM) supplies the TP sensor with a common 5-volt reference circuit, a common low reference circuit, and a signal circuit. The TP sensor signal voltage decreases from more than 4 volts at idle to less than 1 volt at wide open throttle (WOT).
If the ECM detects the TP sensor signal voltage is too low, this DTC 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 ignition is ON or the engine is operating. |
| • | DTC P0122 runs continuously once the conditions above are met. |
Conditions for Setting the DTC
The TP sensor voltage is less than 0.3 volts for more than 2 seconds.
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.
-
This step verifies that a condition exists.
-
This step tests for a condition in the 5-volt reference circuit of the TP sensor. If the DMM does not display more than the specified voltage, test for a short to ground or an open in the 5-volt reference circuit.
-
This step tests for a condition in the signal circuit of the TP sensor. If the TP Voltage parameter does not display more than the specified voltage, test for a short to ground or an open in the signal circuit.
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 - Engine Controls? | -- | Go to Step 2 | |||||||
Is the voltage more than the specified value? | 0.3 V | Go to Step 3 | Go to Step 4 | |||||||
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions | ||||||
Important: Use the J 35616-200 Test Lamp Kit for this test. If the J 35616-200 is not available, use a test lamp that measures more than 20 ohms. Is the voltage more than the specified value? | 4.8 V | Go to Step 5 | Go to Step 6 | |||||||
Is the voltage less than the specified value? | 4.8 V | Go to Step 7 | Go to Step 8 | |||||||
6 |
Important: The 5-volt reference circuits are internally and externally connected at the controller. Other sensors that share the 5-volt reference circuit may also have DTCs set. Disconnecting a sensor on the shared 5-volt reference circuit may isolate a shorted sensor. Review the electrical schematic and diagnose the shared circuits and sensors. Test the 5-volt reference circuit of the TP sensor and all shared 5-volt reference circuits for one of the following conditions:
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 | ||||||
7 | Test the signal circuit of TP sensor for one of the following conditions:
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 | ||||||
8 | Test for an intermittent and for a poor connection at the throttle body assembly. 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 12 | Go to Step 10 | ||||||
9 | 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 12 | Go to Step 11 | ||||||
10 | Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- | ||||||
11 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- | ||||||
12 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 13 | ||||||
13 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||
