Schematic Reference: Engine Controls Schematics
Circuit Description
The throttle position (TP) sensor contains a potentiometer whose resistance value changes along with the throttle valve position. The engine control module (ECM) provides a 5 volt reference voltage to the TP sensor. The ECM reads the voltage across the TP sensor and converts it into the throttle position. The TP sensor resistance decreases as the throttle valve opening increases. When the TP sensor resistance decreases the voltage being monitored at the ECM will increase. And when the TP sensor resistance increases, because the throttle valve opening is decreasing, the voltage being monitored at the ECM will decrease.
Conditions for Setting the DTC
| • | High TP sensor voltage (TP angle is greater than 96%) is indicated at the ECM with the engine running. |
| • | The above condition is met for at least 5 seconds. |
Action Taken When the DTC Sets
| • | The ECM illuminates the malfunction indicator lamp (MIL). |
| • | The ECM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer. |
Conditions for Clearing the MIL/DTC
| • | The MIL turns OFF after three consecutively passing trips without a fault present. |
| • | A History DTC clears after 40 consecutive warm-up cycles without a fault. |
| • | Use the scan tool Clear DTC Information function or disconnect the ECM battery feed in order to clear the DTC. |
Diagnostic Aids
A misadjusted TP sensor could cause a DTC P0123 to set. Refer to Throttle Position Sensor Adjustment .
An intermittent malfunction may be caused by a fault in the TP sensor electrical circuit. Inspect the wiring harness and components for any of the following conditions:
| • | Backed out terminals. |
| • | Improper mating of terminals. |
| • | Broken electrical connector locks. |
| • | Improperly formed or damaged terminals. |
| • | Faulty terminal to wire connections. |
| • | Physical damage to the wiring harness. |
| • | A broken wire inside the insulation. |
| • | Corrosion of electrical connections, splices, or terminals. |
If a DTC P0123 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.
Test Description
The numbers below refer to the step numbers in the Diagnostic Table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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The percentage of TP sensor movement should not be greater than 96% when observing the TP sensor parameter from closed throttle position to wide open throttle.
-
A TP sensor is out of specifications and cannot be adjusted should be replaced.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Is the TP sensor percentage at or greater than the specified value? | 96% | |||
3 |
Is the TP sensor percentage greater than the specified value? | 96% | Go to Diagnostic Aids | |
4 |
Is the voltage between the specified value? | 4 to 6 volts | ||
5 | Probe the TP sensor ground circuit at the TP sensor harness connector, using a test light connected to B+. Is the test light ON? | -- | ||
6 |
Is the TP sensor signal voltage between the specified value? | 0.5 to 1.2 volts | ||
7 |
Was a repair necessary? | -- | ||
8 |
Was a repair necessary? | -- | ||
9 | Check for faulty electrical connections at the TP sensor and repair as necessary. Was a repair necessary? | -- | ||
10 | Check for an open TP sensor ground circuit or a faulty ground circuit connection. Repair as necessary. Refer to Wiring Repairs in Wiring Systems. Was a repair necessary? | -- | ||
Adjust or replace the TP sensor. Refer to Throttle Position Sensor Adjustmentand Throttle Position Sensor Replacement. Is the action complete? | -- | -- | ||
12 | Replace the ECM. Refer to Engine Control Module Replacement. Is the action complete? | -- | -- | |
13 |
Are any DTCs displayed on the scan tool? | -- | Go to the Applicable DTC Table | System OK |
