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Home >> Pontiac >> 2007 >> Vibe Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System & Fuel System - DTC P0452 To DTC P2138 >> DTC P2121 >> Test Description
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Test Description

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

  1. 1:  The Diagnostic System Check - Vehicle 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. 3:  This step determines if DTC P2121 is the result of a hard failure or an intermittent condition.
  3. 4:  This step inspects for an open or a short in the APP sensor 5-volt reference.
  4. 5:  This step inspects for excessive resistance in the reference voltage circuit. If the test lamp does not illuminate at all, there is resistance in the circuit.
  5. 6:  When the 5-volt reference circuit is jumpered to the APP sensor input circuit, the scan tool parameter should read 5 volts.
DTC P2121

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Powertrain Control Module Connector End Views  or  Engine Controls Connector End Views 
1  Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2 Are there any other accelerator pedal position (APP) sensor DTCs set? - Go to Diagnostic Trouble Code (DTC) List - Vehicle Go to Step 3 
3 
  1. Perform the scan tool Clear DTC Information function.
  2. Operate the vehicle within the Freeze Frame conditions as specified.
Does DTC P2121 set?		 - Go to Step 4  Go to Diagnostic Aids
4 
  1. Turn OFF the ignition.
  2. Disconnect the APP sensor electrical connector.
  3. Turn ON the ignition, leaving the engine OFF.
  4. Use a DMM in order to measure the voltage of reference voltage circuit of both APP sensors.
Is the voltage of both APP sensors at the specified value?		 5 V Go to Step 5  Go to Step 8 
5 
  1. Connect a test lamp between the reference voltage circuit and ground of each APP sensor.
  2. Turn ON the ignition, leaving the engine OFF.
Does the test lamp illuminate at least dimly for both sensors?		 - Go to Step 6  Go to Step 8 
6 
  1. Connect a test lamp between the signal circuit and the reference voltage circuit of both APP sensors.
  2. Observe both APP sensor voltages on the scan tool.
Are both APP sensor voltages at the specified value?		 5 V Go to Step 9  Go to Step 7 
7
  1. Test for the following conditions:
  2. Repair as necessary. Refer to Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 11  Go to Step 10 
8 Locate and repair the high resistance in the suspect reference voltage circuit of the APP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs .
Did you complete the repair?		 - Go to Step 11  -
9 Replace the APP sensor. Refer to Accelerator Pedal Position Sensor Replacement .
Did you complete the replacement?		 - Go to Step 11  -
10 Replace the PCM. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?		 - Go to Step 11  -
11
  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.
Did DTC P2121 set?		 - Go to Step 12  Go to Step 2 
12 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 - Vehicle System OK
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