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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1382 (Engine Control System Diagnosis (DTC P0010 To DTC P0128) -- 1.8L (LNK)) >> Diagnosis >> DTC P0120 >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 1:  The Diagnostic System Check-Engine Controls 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. 2:  This step determines if DTC P0120 is the result of a hard failure or an intermittent condition.
  3. 7:  When the 5-volt reference is jumpered to the TP input circuit, the scan tool parameter should read 99 percent.
  4. 8:  When the TP sensor input circuit is jumpered to battery voltage, the scan tool parameter should read 99 percent.
DTC P0120

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
1  Did you perform the Diagnostic System Check-Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2  With the throttle closed, select the TP sensor parameter on the scan tool.
Is the TP sensor percentage within the specified value?		 7 to 11% Go to Step 3  Go to Step 4 
3
  1. Perform the scan tool Clear DTC Information function.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Freeze Frame conditions as specified.
Does DTC P0120 set?		 - Go to Step 4  Go to Diagnostic Aids
4 Is a DTC P0110 or DTC P0115 also set? - Go to Step 13  Go to Step 5 
5 Observe the TP sensor with the throttle closed.
Is the TP sensor percentage near the specified value?		 99% Go to Step 10  Go to Step 6 
6 Observe the TP sensor with the throttle closed.
Is the TP sensor percentage less than the specified value?		 2% Go to Step 7  Go to Diagnostic Aids
7 
  1. Disconnect the TP sensor electrical connector.
  2. Jump the 5-volt reference circuit and the TP sensor input circuit together at the TP sensor harness connector.
  3. Select the TP sensor on the scan tool.
Is the TP sensor percentage more than the specified value?		 90% Go to Step 16  Go to Step 8 
8 
  1. Connect a test lamp between battery voltage and the TP sensor input circuit at the TP sensor harness connector.
  2. Observe the TP sensor on the scan tool.
Is the TP sensor percentage more than the specified value?		 90% Go to Step 9  Go to Step 14 
9
  1. Test the 5-volt reference circuit for an open.
  2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.
Did you find and repair a condition?		 - Go to Step 20  Go to Step 18 
10
  1. Disconnect the TP sensor electrical connector.
  2. Observe the TP sensor on the scan tool.
Is the TP sensor percentage at the specified value?		 0% Go to Step 11  Go to Step 12 
11 Connect a test lamp to B+ and the ground circuit of the TP sensor.
Did the test lamp illuminate?		 - Go to Step 17  Go to Step 15 
12
  1. Test for a short to voltage in the TP sensor input circuit.
  2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.
Did you find and repair a condition?		 - Go to Step 20  Go to Step 19 
13
  1. Test for an open in the TP sensor ground circuit between SP108 and the PCM.
  2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.
Did you find and repair a condition?		 - Go to Step 20  Go to Step 18 
14
  1. Test the TP sensor input circuit for an open or a short to ground.
  2. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.
Did you find and repair a condition?		 - Go to Step 20  Go to Step 18 
15 Repair the open in the TP sensor ground circuit between the sensor and SP108. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 - Go to Step 20  -
16
  1. Test for an intermittent or a poor electrical connection at the TP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
  2. Repair as necessary.
Did you find and repair a condition?		 - Go to Step 20  Go to Step 17 
17 Replace the TP sensor. Refer to Throttle Position (TP) Sensor Replacement .
Did you complete the replacement?		 - Go to Step 20  -
18
  1. Test for an intermittent or a poor electrical connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
  2. Repair as necessary.
Did you find and repair a condition?		 - Go to Step 20  Go to Step 19 
19 Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement .
Did you complete the replacement?		 - Go to Step 20  -
20
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC run and pass?		 - Go to Step 21  Go to Step 2 
21 With a scan tool, observe the stored information, Capture Info.
Does the scan tool display any DTCs that you have not diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List System OK
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