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HOMESERVICE MANUALSBUICK2006TERRAZA CXL, 3.5 L, AWDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 146 (ENGINE CONTROL SYSTEM - 3.6L (LY7) - DTC P0008 TO DTC P0133)DTC P0128TEST DESCRIPTION
2006 Buick Terraza CXL, 3.5 L, AWD

Test Description

2006 Buick Terraza CXL, 3.5 L, AWDSECTION Test Description
WARNING: This page is about a different car, the 2006 Buick LaCrosse and 2006 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 3:  This step tests for excessive resistance in the ECT circuit.
  2. 4:  This step tests for a skewed sensor through the range of temperatures that affects this DTC.
DTC P0128

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Engine Control Module (ECM) 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 in Vehicle DTC Information
2 Is the engine cooling system low on coolant? - Go to Loss of Coolant in Engine Cooling Go to Step 3 
3  Is the customer's concern that the engine does not reach operating temperature or that the heater output is low? - Go to Thermostat Diagnosis (LY7) in Engine Cooling Go to Step 4 
4 
CAUTION: Refer to Road Test Caution in Cautions and Notices.
  1. Operate the vehicle within the Conditions for Running the DTC.
  2. Observe the ECT sensor parameter and the Calculated ECT - Thermostat parameter with a scan tool.
Is the Calculated ECT - Thermostat parameter more than the specified value of the ECT sensor parameter?		 10°C (18°F) Go to Step 6  Go to Step 5 
5
  1. Observe the Freeze Frame/Failure Records for this DTC.
  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 6  Go to Diagnostic Aids
6
IMPORTANT: Return to this diagnostic procedure after you complete the thermostat diagnosis.
Test for the correct operation of the thermostat. Refer to Thermostat Diagnosis (LY7) in Engine Cooling.Did you find and correct the condition?		 - Go to Step 15  Go to Step 7 
7
  1. Turn OFF the ignition.
  2. Disconnect the engine coolant temperature (ECT) sensor.
  3. Connect a 3-amp fused jumper wire between the signal circuit and the low reference circuit of the ECT sensor.
  4. Turn ON the ignition, with the engine OFF.
  5. Observe the ECT sensor parameter with a scan tool.
Is the temperature more than the specified value?		 139°C (282°F) Go to Step 11  Go to Step 8 
8
  1. Connect a 3-amp fused jumper between the signal circuit of the ECT sensor and the engine control module (ECM) housing.
  2. Observe the ECT sensor parameter with a scan tool.
Is the temperature more than the specified value?		 139°C (282°F) Go to Step 9  Go to Step 10 
9 Test the low reference circuit of the ECT sensor for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 12 
10 Test the signal circuit of the ECT sensor for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 12 
11 Test for shorted terminals and poor connections at the ECT sensor. 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 15  Go to Step 13 
12 Test for shorted terminals and poor connections at the ECM. 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 15  Go to Step 14 
13 Replace the ECT sensor. Refer to Engine Coolant Temperature (ECT) Sensor Replacement .
Did you complete the replacement?		 - Go to Step 15  -
14 Replace the ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup and programming.
Did you complete the replacement?		 - Go to Step 15  -
15
  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 16 
16 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information System OK
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.