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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1442 (Engine Control System - Diagnosis - 4.2L (DTC P0507 To DTC P2176)) >> Diagnosis Information & Procedures >> DTC P2176 >> Test Description

Test Description

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

  1. 8:  The throttle valve is spring loaded in a slightly open position and should move in either direction without binding. The throttle valve should always be under spring pressure.
  2. 11:  When the ignition is turned ON, the PCM operates the throttle control motor to verify the integrity of the system prior to start-up. This can be seen by the momentary flash of the test lamp as the ignition is turned ON.
DTC P2176

Step Action 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 - Engine Controls? Go to Step 2  Go to Diagnostic System Check - Engine Controls
2 Are DTCs P0120, P0220, P2120, P2125, P2135, P2138 also set? Go to Diagnostic Trouble Code (DTC) List Go to Step 3 
3
IMPORTANT: The throttle angle and pedal angle may not correspond during this procedure.
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the TP sensor 1 and 2 angle parameters.
  3. Apply and release the accelerator pedal several times.
Does the TP sensor 1 and 2 angle parameters increase as the pedal is applied and decrease as the pedal is released?		 Go to Step 4  Go to Step 5 
4
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Start the engine.
  3. 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 5  Go to Diagnostic Aids
5
  1. Turn ON the ignition, with the engine OFF.
  2. Probe both sides of the TAC fuse with a test lamp.
Does the test lamp illuminate on both sides of the fuse?		 Go to Step 6  Go to Step 16 
6
  1. Turn OFF the ignition.
  2. Probe both sides of the TAC fuse with a test lamp.
Does the test lamp illuminate on both sides of the fuse?		 Go to Step 23  Go to Step 7 
7
  1. Turn OFF the ignition.
  2. Disconnect the powertrain control module (PCM) connector containing the throttle actuator control (TAC) ignition 1 voltage circuit.
  3. Turn ON the ignition.
  4. Probe the ETC ignition 1 voltage circuit with a test lamp.
Does the test lamp illuminate?		 Go to Step 8  Go to Step 24 
8 
  1. Turn OFF the ignition.
  2. Inspect the throttle body for the following conditions. Refer to Diagnostic Aids:
    • A throttle valve that is NOT in the rest position
    • A throttle valve that is binding open or closed
    • A throttle valve that is free to move open or closed WITHOUT spring pressure
Did you find any of these conditions with the throttle body?		 Go to Step 25  Go to Step 9 
9
IMPORTANT: The test lamp may momentarily flash when testing these circuits. This is considered normal.
  1. Disconnect the throttle body harness connector.
  2. Turn ON the ignition, with the engine OFF.
  3. Probe the TAC motor control 1 and 2 circuits with the test lamp connected to ground.
Did the test lamp illuminate and remain illuminated on either circuit?		 Go to Step 13  Go to Step 10 
10
IMPORTANT: The test lamp may momentarily flash when testing these circuits. This is considered normal.
Probe the TAC motor control 1 and 2 circuits with the test lamp connected to battery positive.Did the test lamp illuminate and remain illuminated on either circuit?		 Go to Step 14  Go to Step 11 
11 
  1. Turn OFF the ignition.
  2. Connect the test lamp between the TAC motor control 1 and battery ground.
  3. Observe the test lamp as you turn ON the ignition.
Does the test lamp flash ON and then turn OFF?		 Go to Step 12  Go to Step 15 
12
  1. Turn OFF the ignition.
  2. Connect a test lamp between the TAC motor control 2 circuit and battery ground.
  3. Observe the test lamp as you turn ON the ignition.
Does the test lamp flash ON and then OFF?		 Go to Step 19  Go to Step 15 
13
  1. Turn OFF the ignition.
  2. Disconnect the PCM connector that contains the TAC motor control circuits.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the TAC motor control 1 and 2 circuits with the test lamp connected to ground.
Does the test lamp illuminate?		 Go to Step 21  Go to Step 20 
14
  1. Turn OFF the ignition.
  2. Disconnect the PCM connector that contains the TAC motor control circuits.
  3. Probe the TAC motor control 1 and 2 circuits with the test lamp connected to battery positive.
Does the test lamp illuminate?		 Go to Step 22  Go to Step 20 
15
  1. Turn OFF the ignition.
  2. Disconnect the PCM connector that contains the TAC motor controls circuits.
  3. Test TAC motor control 1 and 2 circuits for an open or high resistance.
  4. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 27  Go to Step 20 
16 Test the ETC/TAC ignition 1 voltage circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 27  Go to Step 17 
17 Test the motor control 1 circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 27  Go to Step 25 
18
  1. Turn OFF the ignition.
  2. Disconnect the PCM connector that contains the TAC motor control circuits.
  3. Test the TAC motor control 1 and 2 circuits for an open or high resistance.
  4. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 27  Go to Step 19 
19 Test for a poor connection or terminal tension at the throttle body connector. 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 27  Go to Step 25 
20 Test for a poor connection or terminal tension 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 27  Go to Step 25 
21 Repair the short to voltage on the circuit where the test lamp remained illuminated. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 27  -
22 Repair the short to ground on the circuit where the test lamp remained illuminated. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 27  -
23 Repair the short to voltage on the ETC ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 27  -
24 Repair the open or high resistance in the ETC ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 27  -
25 Replace the throttle body assembly. Refer to Throttle Body Assembly Replacement .
Did you complete the replacement?		 Go to Step 27  -
26 Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement .
Did you complete the replacement?		 Go to Step 27  -
27
  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 28 
28 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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