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Home >> Chevrolet >> 2005 >> Classic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System (DTC P0106-P0300) >> Diagnosis >> DTC P0122 >> Test Description
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Test Description

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

  1. 5:  The measurement noted in this step will be used in subsequent steps if the measurement is not less than the specified value.
  2. 8:  This step calculates the resistance in the 5-volt reference circuit.
DTC P0122

Step Action Values Yes No
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module (PCM) Connector End Views
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the TP sensor parameter with a scan tool.
Is the voltage less than the specified value?		 0.10 V Go to Step 4  Go to Step 3 
3
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 - Go to Step 4  Go to Intermittent Conditions
4
  1. Turn OFF the ignition.
  2. Remove the air cleaner outlet resonator. Refer to Air Cleaner Outlet Resonator Replacement .
  3. Test for shorted terminals and for a poor connection at the throttle position (TP) sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 18  Go to Step 5 
5 
  1. Turn OFF the ignition.
  2. Disconnect the TP sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the 5-volt reference circuit of the TP sensor to a good ground with a DMM at the TP sensor connector. Note the measurement as "Supply voltage".
Is the voltage more than the specified value?		 4.8 V Go to Step 8  Go to Step 6 
6
  1. Leave the DMM connected.
  2. Disconnect the air conditioning (A/C) refrigerant pressure sensor and the fuel tank pressure (FTP) sensor, one at a time.
  3. Observe the DMM each time a sensor is disconnected.
Does the voltage measure more than the specified value after either of the sensors are disconnected?		 4.8 V Go to Step 15  Go to Step 7 
7
  1. Disconnect the DMM from the TP sensor connector.
  2. Measure the voltage from the 5-volt reference circuit of the A/C refrigerant pressure sensor to a good ground, with the DMM, at the A/C pressure sensor connector.
Is the voltage more than the specified value?		 4.8 V Go to Step 10  Go to Step 13 
8 
  1. Connect a test lamp and a DMM in series between the 5-volt reference circuit and the low reference circuit of the TP sensor at the harness connector.
  2. Measure the amperage with the DMM. Note the measurement as "Amperage".
  3. Remove the DMM from the circuit.
  4. Connect the test lamp between the 5-volt reference circuit and the low reference circuit of the TP sensor at the harness connector.
  5. Measure the voltage from the 5-volt reference circuit at the test lamp to a good ground with the DMM. Note the measurement as "Load voltage drop".
    6. IMPORTANT: Before any calculations are performed, ensure that all measurements are converted to like units. For example, volts/amps or millivolts/milliamps.
  6. Subtract the "Load voltage drop" from the "Supply voltage". Note the result as "Supply voltage drop".
  7. Divide the "Supply voltage drop" by the "Amperage".
Is the result more than the specified value?		 5 ohm Go to Step 11  Go to Step 9 
9
  1. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the TP sensor and the signal circuit of the TP sensor.
  2. Observe the TP sensor parameter with a scan tool
Is the voltage more than the specified value?		 4.9 V Go to Step 16  Go to Step 12 
10 Test the 5-volt reference circuit between the powertrain control module (PCM) and the TP sensor for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 18  Go to Step 14 
11 Test the 5-volt reference circuit between the PCM and the TP sensor for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 18  Go to Step 14 
12 Test the TP sensor signal circuit between the PCM and the TP sensor for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 18  Go to Step 14 
13 Test the 5-volt reference circuits of the following sensors for a short to ground:
  • The TP sensor
  • The A/C refrigerant pressure sensor
  • The FTP sensor

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 18  Go to Step 14 
14 Test for shorted terminals and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 18  Go to Step 17 
15 Replace the component for which the voltage changed. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in Heating, Ventilation, and Air Conditioning or Fuel Tank Pressure Sensor Replacement .
Did you complete the replacement?		 - Go to Step 18  -
16 Replace the TP sensor. Refer to Throttle Position (TP) Sensor Replacement .
Did you complete the replacement?		 - Go to Step 18  -
17 Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.
Did you complete the replacement?		 - Go to Step 18  -
18
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 - Go to Step 2  Go to Step 19 
19 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information System OK
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