Circuit Description
The throttle position (TP) sensor is a potentiometer. The control module supplies the TP sensor a reference voltage, a signal, and ground circuits. When the throttle is depressed, the TP sensor signal rises to near the reference voltage. When the throttle is released, the TP sensor signal decreases from the reference voltage. The control module monitors the TP sensor signal circuit voltage in order to determine the throttle blade angle, or opening.
This DTC is designed to detect a TP sensor signal voltage lower than the possible operating range of a normally functioning TP sensor.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
The TP sensor signal voltage is less than 0.25 volts for 1 second or more.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles. |
| • | The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool Freeze Frame/Failure Records. |
Conditions for Clearing the MIL or DTC
| • | The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed. |
| • | A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle. |
| • | Use a scan tool in order to clear the DTCs. |
Diagnostic Aids
The scan tool reads throttle position in volts. The TP should read about 0.45-0.85 volts 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).
An open or short to ground in the 5 volt reference circuit or the TP sensor signal circuit results in a DTC P0122.
Refer to the Symptoms .
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 volts (1250 mV) when throttle was closed, to over 4.5 volts (4500 mV) when throttle was closed to over 4.5 volts (4500 mV) when throttle is held at the Wide Open Throttle (WOT) position.
An intermittent may be caused by any of the following conditions:
| • | A poor connection |
| • | Rubbed through wire insulation |
| • | A broken wire inside the insulation |
Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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If the TP signal measures less than 0.25 volt, then the low voltage condition exists.
-
If the VCM recognizes the high signal voltage, the VCM and the wiring are okay.
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The 5 volt reference of the VCM supply is shared by the MAP, FTP, TP, and EGR position sensors. A short to ground at ANY of the sensors 5 volt reference circuits OR an internally shorted sensor may cause the DTC to set. In order to determine the location of a shorted 5 volt reference supply, disconnect the sensors one at a time beginning with the MAP sensor.
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The sensor connectors must remain disconnected while the VCM C3 connector remains connected for this step. The VCM terminals C3 12 and C3 27 are spliced together inside the VCM. When checking the 5 volt reference circuit for a short to ground, both the 5 volt reference circuits must be checked.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 |
Important: Before clearing the DTCs, use the scan tool Capture Info to save the Freeze Frame and Failure Records for reference. The control module's data is deleted once the Clear Info function is used. Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||
Does the scan tool display a TP sensor voltage less than the specified value? | 0.25 V | |||||||||
3 | Depress the accelerator pedal to WOT (wide open throttle) while monitoring the TP angle on the scan tool. Does the TP angle increase smoothly through the specified range? | 0-100% | Go to Step 4 | |||||||
4 | The DTC is intermittent. Are any additional DTCs set? | -- | Go to the applicable DTC table | Go to Diagnostic Aids | ||||||
Does the scan tool display a TP sensor voltage more than the specified value? | 4.0 V | Go to Step 13 | Go to Step 6 | |||||||
6 |
Is the voltage more than the specified value? | 4.7 V | Go to Step 14 | Go to Step 7 | ||||||
7 |
Did you find a problem? | -- | Go to Step 19 | Go to Step 8 | ||||||
Did the voltage read more than the specified value after disconnecting on of the sensors? | 4.7 V | Go to Step 9 | Go to Step 12 | |||||||
9 | Was the suspect sensor the EGR sensor? | -- | ||||||||
10 | Check for a short between the 5 volt reference circuit and the EGR feed control circuit. Did you find a problem? | -- | ||||||||
11 |
Is the action complete? | 4.7 V | -- | |||||||
Is the test lamp ON? | -- | Go to Step 16 | Go to Step 17 | |||||||
13 | Check for a poor connection at the TP sensor. Did you find a problem? | -- | ||||||||
14 | Check the TP sensor signal circuit for a short to ground. Did you find a problem? | -- | ||||||||
15 | Check the TP sensor signal circuit for an open. Did you find a problem? | -- | ||||||||
16 | Repair the short to ground in the 5 volt reference circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
17 |
Did you find a problem? | -- | Go to Step 20 | |||||||
18 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Is the action complete? | -- | Go to Step 21 | -- | ||||||
19 | Repair the circuit as necessary. Refer to Connector Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 21 | -- | ||||||
20 |
Is the action complete? | -- | ||||||||
21 |
Does the scan tool indicate the diagnostic Passed? | |||||||||
22 | Does the scan tool display any additional undiagnosed DTCs? | Go to the applicable DTC table | System OK |
