Circuit Description
The Throttle Position (TP) Sensor provides a voltage signal which changes relative to the throttle blade angle. The TP sensor signal voltage varies from about 0.5 volt at idle to about 4.0 volts at Wide Open Throttle (WOT).
The TP sensor signal is used by the TCM for most of the TCM control outputs.
Each time the voltage drops below 1.25 volts and stops, the TCM assumes this value as the 0 throttle angle. The TCM measures the percent throttle from this point on.
Conditions for Setting the DTC
| • | The engine is running. |
| • | TP Sensor Signal is greater than 4.9 volts for greater than 1 second. |
Action Taken When the DTC Sets
Important:: The scan tool will not indicate default values.
| • | The TCM does not illuminate the MIL. |
| • | The TCM commands maximum line pressure. |
| • | The TCM uses 35% TP as a default. |
| • | The TCM inhibits 4th gear if in hot mode. |
| • | DTC 21 is stored in TCM history. |
Conditions for Clearing the DTC
| • | A scan tool can clear the DTC from TCM history. |
| • | The TCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the TCM. |
Diagnostic Aids
The scan tool reads the throttle position in volts. The TP should read about 0.45 to 0.85 volt with the throttle closed and the ignition switch turned ON or at idle. The voltage should increase at a steady rate as the throttle is moved toward the Wide Open Throttle (WOT).
Also, some scan tools will read the throttle angle. 0% = closed throttle. 100% = WOT.
Scan the TP sensor while depressing the accelerator pedal with the engine stopped and the ignition ON. The display should vary from below 1.25 volts (1250 mV) when the throttle was closed, to over 4.5 volts (4500 mV) when the throttle is held at the Wide Open Throttle (WOT) position.
This DTC will result if the TP ground circuit is open or the TP signal circuit is shorted to the voltage.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
If the TP signal measures greater than 4.9 volts, then the fault exists.
-
With the TP sensor disconnected and if the TCM and the wiring are okay, the TP signal should go low.
-
Probing the TP ground circuit with a test lamp checks the 5.0 volt return circuit. This step isolated a faulty sensor, the TCM or an open TP ground circuit.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Important:: Before clearing the DTC's use the Scan Tool in order to record the freeze frame and the failure records for reference because the Clear Info function will lose the data. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
Does the Scan Tool display a TP sensor signal greater than the specified value? | 4.9 V | |||
Does the Scan Tool display a TP sensor signal less than the specified value? | 0.2 V | |||
The DTC is intermittent. If no additional DTC's are stored, refer to the Diagnostic Aids. If additional DTC's are stored, refer to those tables first. Are any additional DTC's stored? | -- | Go to The Applicable DTC Table | -- | |
5 | With a J 39200 DMM connected to ground, probe the 5 V reference circuit (at the TP sensor electrical connector). Is the voltage greater than the specified value? | 5.2 V | ||
6 | Probe the TP sensor ground circuit (at the TP sensor connector) with a test light connected to B +. Is the test lamp on? | -- | ||
7 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Is the action complete? | -- | -- | |
8 | Inspect for a short to voltage in the TP sensor signal circuit. Was a shorted condition found? | -- | ||
9 |
Is the voltage greater than the specified value? | 5.2 V | ||
10 | Inspect for a short to voltage on the 5 V reference circuit (416). Refer to General Electrical Diagnosis . Did you find a short to B + voltage? | -- | Go to Diagnostic Aids | |
11 | Check the sensor ground circuit (452) for an open. Refer to General Electrical Diagnosis . Was an open condition found? | -- | ||
12 | Repair as necessary. Refer to Wiring Repairs . Is the action complete? | -- | -- | |
13 | Repair the short to voltage on the 5 V reference circuit (416). Refer to Wiring Repairs . Is the action complete? | -- | -- | |
14 | Replace the TCM. Important:: If the TCM is faulty, reuse the PROM (Mem-cal). Is the replacement complete? | -- | -- | |
15 |
Is the Scan Tool TP sensor voltage within the specified value? | 0.5-1.25 volts DC | System OK |
