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 the accelerator pedal position (APP) sensor. 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 throttle the 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 4.6 volts DTC P0123 sets.
Conditions for Running the DTC
| • | The battery voltage is more than 10 volts. |
| • | The ignition is ON. |
Conditions for Setting the DTC
The TP sensor 1 voltage is more than 4.6 volts for more than 140 milliseconds.
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. |
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 | |||||||||
2 |
Is the TP sensor 1 voltage more than the specified value? | 4.6 V | Go to Step 5 | Go to Step 3 | ||||||||
3 |
Does the DTC fail this ignition? | -- | Go to Step 5 | Go to Step 4 | ||||||||
4 |
Did the DTC fail this ignition? | -- | Go to Step 18 | Go to Intermittent Conditions | ||||||||
5 |
Is the voltage within the specified range? | 4.8-5.2 V | Go to Step 6 | Go to Step 10 | ||||||||
6 | 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 7 | Go to Step 12 | ||||||||
7 |
Important: It may be necessary to remove the ECM/TCM fuse to allow the ECM to power down. Is the resistance less than the specified value? | 5ohms | Go to Step 15 | Go to Step 8 | ||||||||
8 | Test the low reference circuit of the TP sensor 1 for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 9 | ||||||||
9 | Measure the resistance from the case of the ECM to battery ground. Is the resistance less than the specified value? | 5ohms | Go to Step 16 | Go to Step 14 | ||||||||
10 |
Is the voltage within the specified range? | 4.8-5.2 V | Go to Step 17 | Go to Step 11 | ||||||||
11 | Test the 5-volt reference circuit of the 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 20 | Go to Step 13 | ||||||||
12 | Test the signal circuit of the 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 20 | Go to Step 16 | ||||||||
13 | Test the 5-volt reference circuit of the APP 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 20 | Go to Step 16 | ||||||||
14 | Repair the open or high resistance in the ECM ground circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 20 | -- | ||||||||
15 | 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 20 | Go to Step 18 | ||||||||
16 | Test for an intermittent and for a poor connection at the 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 20 | Go to Step 19 | ||||||||
17 | Test the signal circuit of the APP sensor 2 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 20 | -- | ||||||||
18 | Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement . Did you complete the replacement? | -- | Go to Step 20 | -- | ||||||||
19 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 20 | -- | ||||||||
20 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 21 | ||||||||
21 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||||
