Circuit Description
The throttle position (TP) sensor is a potentiometer. The TP sensor is mounted to the left side of the throttle body. The TP sensor provides a voltage signal that changes relative to throttle blade angle. This signal voltage is one of the most important inputs used by the powertrain control module (PCM). The TP sensor has a 5.0 volt reference, a ground and a signal circuit.
The TP sensor Signal voltage should be near 0.6 volt at idle. The TP sensor voltage should increase to above 4.0 volts at wide open throttle (WOT).
When the PCM senses a signal voltage lower than the normal operating range of the sensor, this DTC sets.
Conditions for Running the DTC
The ignition is in the ON position or the engine is operating.
Conditions for Setting the DTC
| • | The TP sensor signal voltage is less than 0.2 volt. |
| • | The above conditions are present for 10 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A last test failed, or current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Use a scan tool in order to clear the MIL and the DTC. |
Diagnostic Aids
Important:
• Remove any debris from the PCM connector surfaces before servicing
the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM.
Ensure that the gaskets are installed correctly. The gaskets prevent
contaminant intrusion into the PCM. • For any test that requires probing the PCM or component
harness connectors, use theJ 35616
connector test adapter kit. Using this kit prevents
any damage to the harness connector terminals. Refer to
Using Connector Test Adapters
in Wiring Systems.
The PCM 5.0 volt reference circuits are internally connected within the PCM. If all the TP sensor circuits are OK, inspect the MAP sensor and exhaust gas recirculation (EGR) valve for malfunctions.
If it is determined that the DTC occurs intermittently, performing the DTC P1122 diagnostic table may isolate the cause of the fault.
For an intermittent, refer to Symptoms .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
If DTC P1639 sets at the same time, this indicates that the 5 volt reference circuit is either shorted to ground or shorted to a voltage. The 5 volt reference circuit is internally connected within the PCM.
-
This step verifies that a malfunction is present.
-
Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed.
-
This determines if the short is caused from the Accelerator and Servo Control Module (ASM). After repairs are made, reconnect the Accelerator and Servo Control Module (ASM) and clear any DTCs that set when the Accelerator and Servo Control Module (ASM) was disconnected.
-
If the scan tool indicates 5 volts, indicates the TP sensor circuits and PCM are OK.
-
Disconnecting the PCM will allow using the DMM to test continuity of the circuits. This will aid in locating an open or shorted circuit.
-
Disconnecting the PCM will allow using the DMM to test continuity of the circuits. This will aid in locating an open or shorted circuit.
Step
| Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Did DTC P1639 fail this ignition? | -- | |||
Is the TP sensor voltage below the specified value? | 0.2V | |||
Does the scan tool indicate that this diagnostic failed this ignition? | -- | 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.
Is the TP sensor voltage still below the specified value? | 0.2V | Go to Diagnostic System Check - ABS in Antilock Brake System. | ||
Is the TP sensor voltage above the specified value? | 4.7V | |||
7 |
Is the TP sensor voltage above the specified value? | 4.7V | ||
Did you find and correct the condition? | -- | |||
9 |
Did you find and correct the condition? | -- | ||
Did you find and correct the condition? | -- | |||
11 |
Did you find and correct the condition? | -- | ||
12 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Is the action complete? | -- | -- | |
13 |
Important: Program the replacement PCM. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | -- | |
14 |
Does the scan tool indicate that this test ran and passed? | -- | ||
15 | Select the Capture Info option and the Review Info using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK |
