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Home >> Chevrolet >> 2006 >> Avalanche 2500 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - 8.1L - DTC P0506 To DTC U0107 >> DTC P2120 >> Test Description
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Test Description

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

  1. 12:  This test isolates whether the short is to another TAC System circuit in the harness or within the TAC module.
  2. 26:  When the TAC module detects a condition within the TAC System, more than 1 TAC System related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.
DTC P2120

Step Action Values Yes No
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Powertrain Control Module (PCM) 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
IMPORTANT: If DTC P0120 or U0107 is also set, refer to the appropriate DTC for further diagnosis.
  1. Turn ON the ignition with the engine OFF, and with your foot OFF the accelerator pedal.
  2. Observe the accelerator pedal position (APP) sensor 1 voltage with a scan tool.
Does the scan tool indicate the APP sensor 1 voltage is within the specified values?		 0.24-2.24 V Go to Step 3  Go to Step 6 
3 Depress the accelerator pedal to the wide open throttle (WOT) position.
Does the scan tool indicate APP sensor 1 voltage within the specified values?		 0.24-4.49 V Go to Step 4  Go to Step 6 
4
  1. Turn OFF the ignition for 30 seconds.
  2. Turn ON the ignition, with the engine OFF.
  3. Select the diagnostic trouble code (DTC) option using the scan tool.
  4. Lightly touch and move the related engine wiring harnesses and connectors while monitoring the DTC information.
Did this DTC fail this ignition during the above test?		 - Go to Step 24  Go to Step 5 
5
  1. Continue to observe the DTC Information.
  2. Depress the accelerator pedal to WOT, then return the pedal to the rest position.
Did this DTC fail this ignition during the above test?		 - Go to Step 19  Go to Diagnostic Aids
6 Disconnect the APP sensor harness connector.
Does the scan tool indicate the APP sensor 1 voltage is at the specified value?		 0 V Go to Step 7  Go to Step 11 
7 Connect a test lamp between the APP sensor 1 signal circuit and B+.
Does the scan tool indicate the APP sensor 1 voltage is at the specified value?		 5 V Go to Step 8  Go to Step 13 
8 Test the APP sensor 1, 5-volt reference circuit for voltage with a DMM.
Does the DMM indicate voltage within the specified values?		 4.54-5.21 V Go to Step 10  Go to Step 9 
9
  1. Turn OFF the ignition.
  2. Disconnect the throttle actuator motor harness connector.
  3. Remove the air inlet duct from the throttle body assembly.
  4. Turn ON the ignition, with the engine OFF.
  5. Rotate the throttle blade by hand to WOT and hold.
  6. Test the APP sensor 1, 5-volt reference circuit for voltage with a DMM.
Does the DMM indicate voltage within the specified values?		 4.54-5.21 V Go to Step 21  Go to Step 16 
10
  1. Connect a fused jumper between the APP sensor 1 low-reference circuit and the APP sensor 1, 5-volt reference circuit.
  2. Observe the Throttle Position (TP) Sensor 1 Voltage parameter with a scan tool.
Does the scan tool indicate TP sensor 1 voltage at the specified value?		 0 V Go to Step 19  Go to Step 17 
11
  1. Turn OFF the ignition.
  2. Disconnect the throttle actuator control (TAC) module harness connector containing the APP sensor circuits.
  3. Turn ON the ignition, with the engine OFF.
  4. Test the APP sensor 1 signal circuit for a short to voltage with a DMM. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 25  Go to Step 12 
12 
  1. Turn OFF the ignition.
  2. Disconnect the other TAC module harness connector.
  3. Test for a short between the APP sensor 1 signal circuit and all other TAC module circuits with a DMM. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 25  Go to Step 22 
13
  1. Turn OFF the ignition.
  2. Disconnect the TAC module harness connector containing the APP sensor circuits.
  3. Test the APP sensor 1 signal circuit for an open or high resistance with a DMM. Refer to Circuit Testing and Wiring Repairs
Did you find and correct the condition?		 - Go to Step 25  Go to Step 14 
14 Test the APP sensor 1 signal circuit for a short to ground with a DMM. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 25  Go to Step 15 
15
  1. Turn OFF the ignition.
  2. Disconnect the other TAC module harness connector.
  3. Test for a short between the APP sensor 1 signal circuit and all other TAC module circuits with a DMM. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 25  Go to Step 22 
16
  1. Turn OFF the ignition.
  2. Disconnect the TAC module connector containing the APP sensor circuits.
  3. Test the APP sensor 1, 5-volt reference circuit for the following conditions with a DMM:
Did you find and correct the condition?		 - Go to Step 25  Go to Step 22 
17
  1. Disconnect the TAC module connector containing the APP sensor circuits.
  2. Test the APP sensor 1 low-reference circuit for an open or high resistance with a DMM. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 25  Go to Step 18 
18 Test the TAC module ground circuit for an open or high resistance with a DMM. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 25  Go to Step 22 
19 Inspect for poor connections at the harness connector of the APP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals .
Did you find and correct the condition?		 - Go to Step 25  Go to Step 20 
20 Replace the APP sensor assembly. Refer to Accelerator Pedal with Position Sensor Replacement .
Did you complete the repair?		 - Go to Step 25  -
21 Did DTC P0120 set while performing Step 9? - Go to DTC P0120 Go to Step 22 
22 Inspect for poor connections at the harness connector of the TAC module. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals .
Did you find and correct the condition?		 - Go to Step 25  Go to Step 23 
23 Replace the TAC module. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?		 - Go to Step 25  -
24 Repair the intermittent condition as necessary. Refer to Connector Repairs and Wiring Repairs .
Did you complete the repair?		 - Go to Step 25  -
25
  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 26 
26  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 System OK
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