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Home >> Buick >> 2007 >> Allure CXS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System & Fuel System - 3.6L - DTC P0135 To P0420 >> DTC P0140 >> Test Description
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Test Description

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

  1. 2:  This step determines if the condition exists. The HO2S voltage parameter should react immediately to the changes in throttle position when performing this test.
  2. 4:  This step tests the HO2S signal circuit for an open. If a bias voltage is not available, there is a condition with the circuit.
  3. 5:  This step tests the HO2S low reference circuit for an open. If the HO2S voltage does not go below the specified value, there is a condition with the circuit.
DTC P0140

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Engine 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 in Vehicle DTC Information
2 
IMPORTANT: Ensure the heated oxygen sensor (HO2S) is secure before proceeding with this DTC. A loose sensor could cause this DTC to set.
  1. Allow the engine to reach operating temperature.
  2. Cycle the throttle from idle to wide open throttle (WOT) 3 times within 5 seconds.
  3. Observe the HO2S 2 voltage parameter with a scan tool.
Does the voltage go above or below the specified range?		 350-550 mV Go to Step 3  Go to Step 4 
3
  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 4  Go to Intermittent Conditions
4 
  1. Turn OFF the ignition.
  2. Disconnect the HO2S 2 connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage between the signal circuit of the HO2S and a good ground with a DMM.
Is the voltage within the specified range?		 350-550 mV Go to Step 5  Go to Step 6 
5 
  1. Connect a 3-amp fused jumper wire between the signal circuit and the low reference circuit of the HO2S.
  2. Observe the HO2S voltage parameter with a scan tool.
Is the voltage less than the specified value?		 10 mV Go to Step 8  Go to Step 7 
6 Test the HO2S signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 12  Go to Step 9 
7 Test the HO2S low reference circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 12  Go to Step 9 
8 Test for an intermittent and for a poor connection at the HO2S. 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 12  Go to Step 10 
9 Test for an intermittent and for a poor connection at the engine control module (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 12  Go to Step 11 
10 Replace the HO2S. Refer to Heated Oxygen Sensor 2 Replacement .
Did you complete the replacement?		 - Go to Step 12  -
11 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 12  -
12
  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 13 
13 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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