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 less 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.
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 DTC P0122.
Refer to 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) with the throttle was closed, to over 4.5 volts (4500 mV) when the throttle is held at the 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 inspect any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent Conditions and Poor Connections 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, the low voltage condition exists.
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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 this 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 5 volt reference circuits must be checked.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||
Is the voltage less than the specified value? | 0.25 V | |||||||||
3 | Depress the accelerator pedal to wide open throttle (WOT) while monitoring the TP angle on the scan tool. Does the TP angle increase smoothly through the specified range? | 0-100% | ||||||||
4 | The DTC is intermittent. Are any additional DTCs set? | -- | Go to the applicable DTC table | Go to Diagnostic Aids | ||||||
Is the voltage more than the specified value? | 4.0 V | |||||||||
6 |
Is the voltage more than the specified value? | 4.7 V | ||||||||
7 |
Did you find a problem? | -- | ||||||||
Is the voltage more than the specified value after disconnecting one of the sensors? | 4.7 V | |||||||||
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 | -- | |||||||
Does the test lamp illuminate? | -- | |||||||||
13 | Check for a faulty 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? | -- | ||||||||
18 | Replace the TP sensor. Refer to Throttle Position Sensor Replacement . Is the action complete? | -- | -- | |||||||
19 | Repair the circuit as necessary. Refer to Wiring Repairs or to Connector Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||
20 |
Important: The replacement VCM must be programmed. Replace the VCM. Refer to VCM Replacement/Programming . 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 |
