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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1865 (Engine Controls And Fuel - 3.5L (L66) - DTC P0506 To DTC P2199) >> DTC P1128 >> Test Description

Test Description

WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers in the diagnostic table:

  1. 1:  The Diagnostic System Check - Vehicle prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool, if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
  2. 5:  This step checks for the correct reference circuit voltage. The scan tool display of MAP sensor voltage will indicate more than 5 volts with an open in the sensor input circuit. This is caused by the scan tool software and should be considered normal.
  3. 6:  This step checks the integrity of the MAP sensor signal circuit.
  4. 11:  After replacing the PCM, a new minimum throttle position and idle speed must also be established.
DTC P1128

Step Action Values Yes No
Connector End View Reference: Powertrain Control Module 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 Is there a DTC P0641 also set? - Go to DTC P0641  Go to Step 3 
3
  1. Turn ON the ignition, with the engine OFF.
  2. Select the manifold absolute pressure (MAP) sensor parameter on the scan tool.
Is the MAP sensor display at or below the specified value?		 0.23 V Go to Step 5  Go to Step 4 
4
  1. Turn OFF the ignition.
  2. Start the engine.
  3. Operate the vehicle within the Freeze Frame conditions as noted.
  4. Observe the MAP sensor voltage on the scan tool.
Did a DTC P1128 set or did the MAP sensor voltage go below the specified value?		 0.23 V Go to Step 5  Go to Diagnostic Aids
5 
  1. Turn OFF the ignition.
  2. Disconnect the MAP sensor electrical connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the 5-volt reference circuit to ground, harness side with a DMM.
Is the voltage near the specified value?		 5.0 V Go to Step 6  Go to Step 8 
6 
  1. Turn OFF the ignition.
  2. Jumper the 5-volt reference circuit of the MAP sensor to the MAP sensor signal circuit.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the MAP sensor voltage on the scan tool.
Is the scan tool voltage near the specified value?		 5.0 V Go to Step 7  Go to Step 9 
7 Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement .
Did you complete the replacement?		 - Go to Step 12  -
8
  1. Check for an open in the 5-volt reference circuit between the powertrain control module (PCM) and the MAP sensor.
  2. Repair as necessary. Refer to Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 12  Go to Step 11 
9
  1. Check for an open in the signal circuit between the PCM and the MAP sensor.
  2. Repair as necessary. Refer to Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 12  Go to Step 10 
10
  1. Inspect the PCM and the MAP sensor electrical connectors for faulty terminal contact. Refer to Testing for Intermittent Conditions and Poor Connections .
  2. Repair as necessary.
Did you find and correct the condition?		 - Go to Step 12  Go to Step 11 
11 
  1. Replace the PCM. Refer to Control Module References for replacement, setup, and programming.
  2. Perform the idle learn procedure. Refer to Idle Learn .
Did you complete the replacement?		 - Go to Step 12  -
12
  1. Use the scan tool in order to clear the DTCs.
  2. Turn the ignition OFF for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC or until the DTC P1128 diagnostic has passed.
Does the DTC run and pass?		 - Go to Step 13  Go to Step 2 
13 With a scan tool, observe the stored information, Capture Info.
Does the scan tool display any DTCs that you have not diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List - Vehicle System OK
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