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Home >> Chevrolet >> 2001 >> Venture Base, Van Passenger >> Repair and Diagnosis >> External Pages >> Different car >> Section 833 (Engine Controls Diagnostic (DTC P0491 To DTC P2130) -- 5.7L) >> Diagnosis >> DTC P2120 >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 Chevrolet Corvette. 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. 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 that 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. Keep this in mind when reviewing the Capture Info.
DTC P2120

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View References:  Powertrain Control Module (PCM) Connector End Views  or  Engine Controls Connector End Views 
1 Did you perform the Diagnostic System Check-Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2
IMPORTANT: If DTC P1518 or P0120 is also set, refer to the appropriate DTC for further diagnosis.
  1. Turn ON the ignition, with the engine OFF and 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 APP sensor 1 voltage within the specified values?		 0.25-2.2 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?		 2.24-4.2 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 DTC option on the scan tool.
  4. Lightly touch and move the related engine wiring harnesses and the 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 and then return the pedal to the released 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 APP sensor 1 voltage 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 APP sensor 1 voltage 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?		 4.6-5.4 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.
  5. Manually rotate the throttle blade 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?		 4.6-5.4 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 the TP sensor 1 voltage is 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 in Wiring Systems.
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 in Wiring Systems.
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 for high resistance, with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
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 in Wiring Systems.
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 in Wiring Systems.
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 an open or for high resistance, with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
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 for high resistance, with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
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 for high resistance, with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
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 in Wiring Systems.
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 Position (APP) Sensor Replacement .
Did you complete the repair?		 - Go to Step 25  -
21 Did DTC P1120 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 in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 25  Go to Step 23 
23 Replace the TAC module. Refer to Throttle Actuator Control (TAC) Module Replacement .
Did you complete the repair?		 - Go to Step 25  -
24 Repair the intermittent condition as necessary. Refer to Connector Repairs and Wiring Repairs in Wiring Systems.
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.
Does the DTC run and pass?		 - Go to Step 26  Go to Step 2 
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 System OK
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