P0120

CIRCUIT DESCRIPTION




The DTC P0120 Throttle Position (TP) Sensor Circuit diagnostic detects an out of range sensor signal. The TP sensor is a potentiometer whose resistance value changes along with the throttle valve position. The powertrain control module (PCM) provides a 5-volt reference voltage to the TP sensor. The PCM reads the voltage across the TP sensor and uses the voltage to calculate the percentage of throttle valve opening. The TP sensor resistance decreases as the throttle valve opening increases. When the TP sensor resistance decreases the voltage being monitored by the PCM increases. The TP sensor resistance increases when the throttle valve opening decreases, therefore the voltage being monitored by the PCM will decrease.

CONDITIONS FOR RUNNING THE DTC
The ignition is ON.

CONDITIONS FOR SETTING THE DTC
- The TP sensor input to the PCM is less than 0.1 volt.

OR

- The TP sensor input to the PCM is more than 4.9 volts.

ACTION TAKEN WHEN THE DTC SETS
- The PCM illuminates the malfunction indicator lamp (MIL).
- The PCM stores the conditions that were present when the DTC set as Freeze Frame data.
- The TP sensor angle will default to 0 percent.

CONDITIONS FOR CLEARING THE MIL/DTC
- The PCM turns OFF the MIL on the third consecutive trip in which the diagnostic runs without a fault.
- The PCM clears a History DTC after 40 consecutive warm-up cycles without a fault.
- You use the scan tool Clear DTC Information function.

DIAGNOSTIC AIDS
If DTCs P0110, P0115, and P0120 are also set, the malfunction may be in the sensor ground circuit.

On a good TP sensor the scan tool will typically display a TP angle of 8-10 percent at idle, and 76-77 percent at wide open throttle (WOT).

An intermittent malfunction may be caused by fault in the TP sensor electrical circuit. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions. Intermittent Conditions

Repair any electrical circuit faults that were found. Refer to Diagnostic Aids for Circuit Testing and Wiring Repair Procedures.

The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.

TEST DESCRIPTION

Steps 1-5:

Steps 6-11:

Steps 12-17:

Steps 18-21:

The numbers below refer to the step numbers on the diagnostic table.
1. The Diagnostic System Check-Computers and Controls Systems prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
2. This step determines if DTC P0120 is the result of a hard failure or an intermittent condition.
7. When the 5-volt reference is jumpered to the TP input circuit, the scan tool parameter should read 99 percent.
8. When the TP sensor input circuit is jumpered to battery voltage, the scan tool parameter should read 99 percent.