Circuit Description
The throttle position (TP) sensor is used by the PCM in order to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer sensor with a 5-volt reference circuit, a low reference circuit, and a signal circuit. Rotation of the TP sensor from the closed throttle position to the wide open throttle (WOT) position provides the PCM with a signal voltage from below 1.0 volt to more than 4 volts through the TP sensor signal circuit. If the PCM detects an excessively high signal voltage, this DTC will set.
Conditions for Running The DTC
The ignition is ON.
Conditions for Setting The DTC
| • | The TP sensor signal voltage is more than 4.75 volts. |
| • | The condition is present for 10 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. |
Diagnostic Aids
The PCM 5-volt reference circuits are internally connected within the PCM. If all the TP sensor circuits are OK, inspect the MAP sensor for malfunctions.
If the DTC occurs intermittently, performing the DTC P1121 diagnostic test may isolate the cause of the fault. Refer to DTC P1121 .
For an intermittent condition , refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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If DTC P1635 sets at the same time, the 5-volt reference circuit is shorted to a voltage. The 5-volt reference circuit is internally connected within the PCM.
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This step verifies if the fault is present.
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Using Freeze Frame/Failure Records data may help to locate an intermittent condition. If you cannot duplicate the DTC, the information in the Freeze Frame/Failure Records can help to determine how many miles have occurred since the DTC set. The Fail Counter and the Pass Counter can also help to determine how many ignition cycles have occurred since the diagnostic reported a pass and/or a fail. In order to isolate when the DTC failed, operate the vehicle within the same Freeze Frame conditions that you observed. These conditions include the RPM, the vehicle load, the vehicle speed, and the temperature.
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This procedure will determine if the short is caused from the Accelerator and Servo Control Module (ASM).
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This tests whether the ground circuit is available to the TP sensor. Inspect for poor electrical connections at the TP sensor.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
Did DTC P1635 or P1639 set? | -- | Go to Step 3 | ||
Does the scan tool indicate that the TP sensor voltage or the Throttle Angle are above the specified values? | 4.7 V, 0% | Go to Step 5 | Go to Step 4 | |
Does the scan tool indicate that this diagnostic failed this ignition? | -- | Go to Step 5 | Go to Diagnostic Aids | |
|
Important: After you complete this diagnosis reconnect the Accelerator and Servo Control Module (ASM). Also, clear any ASM DTCs that may have set when the ASM was disconnected.
Does the scan tool indicate that the TP sensor voltage is above the specified value? | 4.7 V | Go to Step 6 | Go to Diagnostic System Check - ABS in Antilock Brake System | |
6 |
Does the scan tool indicate TP sensor voltage below the specified value? | 0.20 V | Go to Step 7 | Go to Step 10 |
Probe the low reference circuit at the TP sensor harness connector with the J 35616-200 test lamp connected to B+. Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 11 | |
8 | Measure the voltage at the 5-volt reference circuit to ground using the DMM. Does the scan tool indicate that the voltage is more than the specified value? | 5 V | Go to Step 14 | Go to Step 9 |
9 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- |
10 |
Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 13 |
11 |
Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12 |
12 |
Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 13 |
13 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- |
14 | Repair the 5-volt reference circuit for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 15 | -- |
15 |
Does the DTC run and pass? | -- | Go to Step 16 | Go to Step 2 |
16 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
