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 ECM detects that the TP sensor voltage is less than 0.2 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 coolant fan turns ON. |
| • | The ECM will default to 20°C (68°F) for the first 60 seconds of the engine run time, and then 92°C (198°F). The scan tool will not show the defaulted 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 10 seconds. |
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? | 0.2 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 | Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||
