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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1471 (Engine Control System - Diagnosis - 4.2L (DTC P0013 To DTC P0138)) >> Diagnosis Information & Procedures >> DTC P0068 >> Test Description

Test Description

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

  1. 5:  This step will determine if the manifold absolute pressure (MAP) sensor voltage is within the proper range at idle.
  2. 6:  This step will determine if the MAP sensor responds properly to the change in manifold pressure.
  3. 7:  A throttle blade that sticks or binds may set this code. Opening the throttle through the entire range will indicate problems such as these.
  4. 9:  When the PCM detects a condition within the ETC system other DTCs may set due to the many redundant tests run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Keep this in mind when reviewing captured DTC info.
DTC P0068

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-Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2 Are any other DTCs set? - Go to Diagnostic Trouble Code (DTC) List Go to Step 3 
3
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition.
  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 Diagnostic Aids
4 Inspect for the following conditions:
  • Vacuum hoses for splits, kinks, and proper connections as shown on Vehicle Emission Control Information label-Inspect thoroughly for any type of leak or restriction.
  • Air leaks at throttle body mounting area and intake manifold sealing surfaces

Did you find and correct the condition?		 - Go to Step 8  Go to Step 5 
5 
  1. Allow the engine to reach operating temperature.
  2. Observe the MAP sensor voltage parameter with a scan tool.
Is the manifold absolute pressure (MAP) sensor voltage within the specified range?		 0.8-4 V Go to Step 6  Go to DTC P0106 
6 
  1. Idle the engine.
  2. Observe the MAP sensor kPa parameter with a scan tool.
  3. Increase the engine speed slowly and then back to idle.
Does the MAP sensor kPa change smoothly and gradually as engine speed is increased and returned to idle?		 - Go to Step 7  Go to DTC P0106 
7 
    CAUTION: Turn OFF the ignition before inserting fingers into the throttle bore. Unexpected movement of the throttle blade could cause personal injury.
  1. Inspect the throttle body for the following conditions while modulating the throttle through the entire range using the scan tool:
    • Loose or damaged throttle blade
    • Broken throttle shaft
    • Drive mechanism damage
  2. If any of these conditions exist, replace the throttle body assembly. Refer to Throttle Body Assembly Replacement .
Did you find and correct the condition?		 - Go to Step 6  Go to Diagnostic Aids
8
  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 7 
9  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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