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Home >> Pontiac >> 2007 >> Vibe Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System & Fuel System - DTC P0010 To DTC P0128 >> DTC P0128 >> Test Description
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Test Description

The numbers below refer to the step numbers on 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. 2:  This step compares the ECT temperature to the IAT temperature. This inspection is to be performed when the vehicle has reached ambient room temperature. At that time both the surrounding air temperature and the engine coolant temperature are nearly equal. If the ECT sensor and circuit are OK, both sensors should indicate the same temperature.
  3. 3:  This step checks that the temperature of the engine coolant increases at least 20°C (36°F) within 10 minutes. If the temperature does not increase at least 20°C (38°F) there is a fault with the ECT sensor or the engine cooling system.
  4. 6:  Fault not present indicates the condition that caused DTC P0128 to set is intermittent and not currently present. If no other DTCs are stored, refer to Diagnostic Aids for additional information on diagnosing an intermittent DTC P0128.
DTC P0128

Step Action Values Yes No
Schematic Reference: Engine Controls Schematics
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 
  1. Allow the engine to cool to the ambient temperature.
  2. Turn ON the ignition, with the engine OFF.
  3. Compare the engine coolant temperature (ECT) sensor temperature reading to the intake air temperature (IAT) sensor temperature reading on a scan tool.
Are the ECT and the IAT readings within 2 or 3 degrees of each other?		 - Go to Step 3  Go to Step 6 
3 
  1. Start the engine and immediately observe the ECT on the scan tool.
  2. Continue to observe the ECT while idling the engine for 10 minutes.
Does the ECT indicated on the scan tool increase by more than the specified value within the 10 minutes?		 20°C (36°F) Go to Step 5  Go to Step 4 
4 Are any ECT sensor DTCs set? - Go to DTC P0115  or DTC P0116  Go to Step 8 
5 The fault is not present.
Are there any DTCs stored that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List - Vehicle Go to Diagnostic Aids
6 
  1. Measure the resistance of the ECT sensor with a DMM.
  2. Compare the measured resistance of the ECT sensor with the resistance values in the Temperature vs Resistance table. Refer to Temperature Versus Resistance .
Is the resistance of the ECT sensor within specifications?		 - Go to Step 7  Go to Step 9 
7
  1. Check for any of the following conditions:
    • A high resistance in the ECT sensor wiring
    • A poor connection at the ECT sensor
    • A poor connection at the powertrain control module (PCM)
  2. Repair as necessary. Refer to Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 11  Go to Step 10 
8
  1. Inspect the engine cooling system for all of the following:
  2. Repair as necessary.
Did you complete the action?		 - Go to Step 11  -
9 Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement .
Did you complete the replacement?		 - Go to Step 11  -
10 Replace the PCM. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?		 - Go to Step 11  -
11
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC run and pass?		 - Go to Step 12  Go to Step 2 
12 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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