Circuit Description
The Throttle Position (TP) sensor provides a voltage signal that changes relative to the throttle opening. The TP sensor signal voltage varies from about 0.6 volt at idle to about 4.8 volts at wide open throttle (WOT).
The TP sensor signal is an important input used by the ECU for fuel trim and diagnostic functions.
This is a type B DTC.
Conditions for Setting the DTC
The following conditions will set the DTC:
| • | The vehicle is in the CNG operation mode. |
| • | The engine is running. |
| • | The TPS circuit voltage is less than 0.09 volt. |
Action Taken When the DTC Sets
The ECU sets the DTC 22 after 2 consecutive driving trips with the fault active.
Conditions for Clearing the MIL/DTC
The ECU turns the MIL OFF after 3 consecutive driving trips without a fault condition present. A DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 40°C (72°F) from the start-up coolant temperature and the engine coolant temperature exceeds 70°C (160°F) during that same ignition cycle) or the code clearing procedure has been used.
Diagnostic Aids
Always diagnose ANY VCM codes that are present before beginning this diagnostic procedure.
A scan tool displays the throttle position in volts. It should display 0.40 volt to 0.90 volt with the throttle closed and the ignition ON or at idle. The voltage should increase at a steady rate as the throttle is moved toward Wide Open Throttle (WOT). The scan tool also displays the throttle angle percentage where 0% = closed and 100% = WOT.
Scan the TP sensor signal while depressing the accelerator pedal with the engine stopped and the ignition ON. The display should vary from below 1.25 when the throttle is closed to over 4.5 volts when the throttle is held 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.
Refer to Intermittent Conditions if the DTC is intermittent.
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
-
The fault exists if the TP sensor signal measures less than 0.15 volt.
-
This test determines if the fault exists in the ECU or the VCM wiring.
-
This test simulates DTC 21 (high voltage). The wiring and the ECU are OK if the VCM recognizes the high signal voltage.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Alternative Fuels (AF) Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Alternative Fuels (AF) Powertrain On Board (OBD) System Check |
Does the scan tool display a throttle position signal less than the specified value? | 0.15 V | Go to Step 3 | Go to Step 6 | |
Disconnect ECU connector C001. Does the scan tool display a throttle position signal less than the specified value? | 0.15 V | Go to Step 4 | Go to Step 8 | |
Does the scan tool display a throttle position signal greater than the specified value? | 4.0 V | Go to Step 17 | Go to Step 5 | |
5 | Probe the TP sensor signal circuit with a test lamp connected to B+. Does the scan tool display a throttle position signal over the specified value? | 4.0 V | Go to Step 11 | Go to Step 13 |
6 |
Does the DVOM display the TP sensor signal less than the specified value? | 0.09 V | Go to Step 7 | Go to Step 10 |
7 |
Is there continuity? | -- | Go to Step 8 | Go to Step 13 |
8 | Inspect the ECU connector for loose, corroded or damaged pins. Was a problem found? | -- | Go to Step 16 | Go to Step 9 |
9 | Replace the ECU. Refer to Engine Control Unit Replacement . Is the action complete? | -- | Go to Step 19 | -- |
10 | The DTC is intermittent. Refer to Diagnostic Aids if no additional DTCs are stored. If additional DTCs are stored, refer to those tables. Are any additional DTCs set? | -- | Go to the applicable DTC table | -- |
11 | Check for an open in the 5 volt reference circuit. Was a problem found? | -- | Go to Step 16 | Go to Step 12 |
12 | Check the 5 volt reference for a short to ground. Was a problem found? | -- | Go to Step 16 | Go to Step 15 |
13 | Check the TP sensor signal circuit for an open. Was a problem found? | -- | Go to Step 16 | Go to Step 14 |
14 | Check the TP sensor signal circuit for a short to ground. Was a problem found? | -- | Go to Step 16 | Go to Step 15 |
15 | Check for a faulty connection at the VCM. Was a problem found? | -- | Go to Step 16 | Go to Step 18 |
16 | Repair the circuit as necessary. Refer to Repair Procedures in Electrical Diagnosis in the C/K Truck Service Manual. Is the action complete? | -- | Go to Step 19 | -- |
17 | Replace the faulty TP sensor. Refer to TP Sensor Replacement in Engine Controls - 5.0, 5.7L in the C/K Truck Service Manual. Is the action complete? | -- | Go to Step 19 | -- |
18 | Replace the VCM. Important:: Reprogram the VCM if it is faulty. Refer to VCM Replacement/Programming in Engine Controls - 5.0, 5.7L in the C/K Truck Service Manual. Is the action complete? | -- | Go to Step 19 | -- |
19 |
Does the diagnostic run and pass? | -- | Go to Step 20 | Go to Step 2 |
20 | Select the Capture Information mode on the scan tool and review the information. Are any DTCs displayed that have not been diagnosed? | -- | Go to the applicable DTC table | System OK |
