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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1538 (Engine Controls Diagnostic (DTC P0491 To DTC P2130) -- 5.7L) >> Diagnosis >> DTC P2126 >> 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 steps numbers in the diagnostic table.

  1. 2:  This step determines if a communication condition exists.
  2. 5:  This step isolates an internal APP sensor failure. The condition may only occur at a certain accelerator pedal position. Monitoring the APP angles for sensor 1 and sensor 3 is an accurate way of verifying the actual position of the pedal.
  3. 6:  The APP sensor 2 shares a common 5-volt reference circuit with the TP sensor 2. Monitoring the TP sensor 2 voltage aids in diagnosing the APP sensor 5-volt reference and low reference circuits. If the scan tool displays near 0 volts then the circuits are OK.
  4. 18:  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 P2126

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  Is DTC U0107 also set? - Go to DTC U0107 Go to Step 3 
3
IMPORTANT: Do not depress the accelerator pedal.
  1. Turn OFF the ignition for 15 seconds.
  2. Start the engine.
  3. Observe the DTC Info, with a scan tool.
Did any other throttle actuator control (TAC) module or accelerator pedal position (APP) sensor DTCs set except P1125?		 - Go to Diagnostic Trouble Code (DTC) List Go to Step 4 
4 Observe the APP sensor Agree/Disagree parameters, with a scan tool.
Does the scan tool indicate Disagree for any of the APP sensors Agree/Disagree parameters?		 - Go to Step 6  Go to Step 5 
5 
  1. Turn OFF the ignition.
  2. Turn ON the ignition, with the engine OFF.
  3. Observe the APP sensor angles for all 3 APP sensors, with a scan tool.
  4. Slowly depress the accelerator pedal, stopping at 25, 50, 75, and 100 percent.
  5. Slowly release the accelerator pedal, stopping at 75, 50, 25, and 0 percent.
Does the scan tool indicate that the APP sensor 2 angle is within 10.5 percent of the APP sensor 1 angle, and that the APP sensor 2 angle is within 13 percent of the APP sensor 3 angle during the above test?		 - Go to Diagnostic Aids Go to Step 6 
6 
  1. Turn OFF the ignition.
  2. Disconnect the APP sensor harness connector.
  3. Connect a fused jumper between the APP sensor 2 5-volt reference circuit and ground.
  4. Turn ON the ignition, with the engine OFF.
  5. Observe the throttle position (TP) sensor 2 voltage parameter, with a scan tool.
Does the scan tool indicate TP sensor 2 voltage at the specified value?		 0 V Go to Step 7  Go to Step 11 
7
  1. Connect a fused jumper between the APP sensor 2 5-volt reference circuit and the APP sensor 2 low reference circuit.
  2. Observe the TP sensor 2 voltage parameter, with a scan tool.
Does the scan tool indicate TP sensor 2 voltage at specified value?		 0 V Go to Step 8  Go to Step 11 
8
  1. Turn OFF the ignition.
  2. Disconnect the TAC module harness connector containing the APP circuits.
  3. Test the APP sensor 2 signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 17  Go to Step 9 
9
  1. Turn OFF the ignition.
  2. Test for a short between the APP sensor 2 signal circuit and all other APP circuits at the APP sensor harness connector.
Does the DMM indicate a short to another circuit?		 - Go to Step 10  Go to Step 13 
10
  1. Disconnect the TAC module harness connector containing the APP sensor circuits.
  2. Test for a short between the APP sensor 2 signal circuit and all other APP circuits at the APP sensor harness connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 17  Go to Step 13 
11
  1. Turn OFF the ignition.
  2. Disconnect the TAC module harness connector containing the APP circuits.
  3. Test the APP sensor 2 5-volt reference circuit for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 17  Go to Step 12 
12 Test the APP sensor 2 low reference circuit for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 17  Go to Step 14 
13 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 17  Go to Step 15 
14 Inspect for poor connections at the harness connectors 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 17  Go to Step 16 
15 Replace the accelerator pedal assembly. Refer to Accelerator Pedal Position (APP) Sensor Replacement .
Did you complete the replacement?		 - Go to Step 17  -
16 Replace the TAC module. Refer to Throttle Actuator Control (TAC) Module Replacement .
Did you complete the replacement?		 - Go to Step 17  -
17
  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 18 
18  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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