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Home >> Chevrolet >> 2005 >> Classic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System (DTC P0106-P0300) >> Diagnosis >> DTC P0140 >> Test Description
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Test Description

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

  1. 2:  An HO2S heater fault may set this DTC.
  2. 3:  If the voltage is varying above and below the specified value, the condition is not present.
DTC P0140

Step Action Value(s) 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 - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2 
  1. Turn ON the ignition, with the engine OFF.
  2. Command the heated oxygen sensor (HO2S) 2 heater ON with a scan tool.
  3. Wait 15 seconds to allow the HO2S 2 heater current to stabilize.
  4. Observe the HO2S 2 heater current parameter with a scan tool.
Is the HO2S 2 heater current parameter within the specified range?		 0.217-1.56 A Go to Step 3  Go to DTC P0141 
3 
  1. Start the engine.
  2. Allow the engine to reach operating temperature. Refer to Scan Tool Data List .
  3. Operate the engine at 2,000 RPM for 30 seconds.
  4. Quickly cycle the throttle from closed throttle to wide open throttle 3 times, while observing the HO2S 2 voltage parameter with a scan tool.
Did the HO2S 2 change more than the specified value?		 200 mV Go to Step 4  Go to Step 5 
4
  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 5  Go to Intermittent Conditions
5
  1. Turn OFF the ignition.
  2. Disconnect the HO2S 2.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the HO2S 2 voltage parameter with a scan tool.
Is the HO2S 2 voltage parameter more than the specified value?		 800 mV Go to Step 6  Go to Step 7 
6
IMPORTANT: The normal voltage on the high signal circuit is between 400-500 mV.
IMPORTANT: The sensor may be damaged if the circuit is shorted to a voltage source.
Test the HO2S 2 high signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you find and correct the condition?		 - Go to Step 18  Go to Step 17 
7
  1. Connect a 3-amp fused jumper wire between the high signal circuit of the HO2S 2 harness connector on the engine harness side and the low signal circuit of the HO2S 2 harness connector on the engine harness side.
  2. Observe the HO2S 2 voltage parameter with a scan tool.
Is the HO2S 2 voltage parameter within the specified range?		 400-500 mV Go to Step 9  Go to Step 8 
8
  1. Remove the jumper wire from the previous step.
  2. Test the HO2S 2 heater low control circuit for a short to one of the following circuits:
Did you find and correct the condition?		 - Go to Step 18  Go to Step 14 
9
  1. Remove the jumper wire from the previous step.
  2. Connect a 3-amp fused jumper wire from the high signal circuit of the HO2S 2 harness connector on the engine harness side and ground.
  3. Observe the HO2S 2 voltage parameter with a scan tool.
Is the HO2S 2 voltage parameter within the specified range?		 400-500 mV Go to Step 11  Go to Step 10 
10
  1. Remove the jumper wire from the previous step.
  2. Test the HO2S 2 low signal circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 18  Go to Step 15 
11
  1. Remove the jumper from the previous step.
  2. Measure the voltage from the high signal circuit of the HO2S 2 harness connector on the engine harness side to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.
Is the voltage more than the specified value?		 1 V Go to Step 12  Go to Step 13 
12
IMPORTANT: The normal voltage on the low signal circuit is between 20-100 mV.
Test the HO2S 2 low signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.Did you find and correct the condition?		 - Go to Step 18  Go to Step 17 
13 Test the HO2S 2 high signal circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 18  Go to Step 15 
14 Test for an intermittent and for a poor connection at the HO2S 2. 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 18  Go to Step 16 
15 Test for an intermittent and for a poor connection at the powertrain control module (PCM). 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 18  Go to Step 17 
16 Replace the HO2S 2. Refer to Heated Oxygen Sensor (HO2S) Replacement (Bank 1) or Heated Oxygen Sensor (HO2S) Replacement (Bank 2) .
Did you complete the replacement?		 - Go to Step 18  -
17 Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.
Did you complete the replacement?		 - Go to Step 18  -
18
  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 19 
19 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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