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 high, this DTC sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage
Conditions for Running the DTC
| • | The ignition is ON or the engine is operating. |
| • | DTC P0123 runs continuously once the conditions above are met. |
Conditions for Setting the DTC
The TP sensor voltage is more than 4.89 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 determines whether a condition exists in the idle switch position circuit of the throttle body. If DTC P0223 sets in addition to DTC P0123, repair the idle switch position circuit for a short to battery positive voltage.
-
This step tests for a condition in the signal circuit of the TP sensor. If the TP Voltage parameter displays a voltage after the throttle body is disconnected, test for a short to voltage in the signal circuit.
-
This step isolates if there is a circuit that is shorted to voltage. Or, if the low reference circuit is open internally or externally of the ECM. If there is no voltage on the low reference circuit after disconnecting the engine coolant temperature (ECT) sensor, test the low reference circuit for an open.
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 less than the specified value? | 4.89 V | Go to Step 3 | Go to Step 4 | |
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions |
Observe the DTC information with a scan tool. Did DTC P0223 also set. | -- | Go to Step 14 | Go to Step 5 | |
Is the voltage less than the specified value? | 0.1 V | Go to Step 6 | Go to Step 9 | |
6 | Measure the voltage between the 5-volt reference circuit of the TP sensor and the ECM housing with a DMM. Is the voltage less than the specified value? | 5.2 V | Go to Step 7 | Go to Step 10 |
7 |
Notice: Do NOT use a test lamp to test the continuity of the circuit. Damage to the control module may occur due to excessive current draw. Is the resistance more than the specified value? | 10 ohms | Go to Step 8 | Go to Step 12 |
Is the voltage less than the specified value. | 1 V | Go to Step 11 | Go to Step 15 | |
9 | Test the signal circuit of TP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 13 |
10 |
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 a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 13 |
11 |
Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 13 |
12 | Test for shorted terminals and for poor connections 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 18 | Go to Step 16 |
13 | Test for shorted terminals and for poor connections 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 18 | Go to Step 17 |
14 |
Important: The control module and/or the throttle body assembly may be damaged if the circuit is shorted to battery positive voltage.
Did you complete the repair? | -- | Go to Step 18 | -- |
15 |
Important: The control module and/or the throttle body assembly may be damaged if the circuit is shorted to battery positive voltage. Repair the short to voltage in the low reference circuit of the TP sensor. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 18 | -- |
16 | Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement . Did you complete the replacement? | -- | Go to Step 18 | -- |
17 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 18 | -- |
18 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 19 |
19 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
