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Home >> Cadillac >> 2004 >> CTS Base, 3.6 7 >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 12 (Engine Controls - 2.6L & 3.2L - Diagnosis (DTC P0030 - P0174)) >> Diagnostic Trouble Codes >> DTC P0140 or P0160 >> Test Description

Test Description

WARNING: This page is about a different variant/trim than selected.

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

  1. 9:  This test verifies whether or not the affected HO2S is internally shorted to voltage prior to replacing the ECM.
  2. 14:  Both components must be replaced since the shorted HO2S has damaged the ECM low reference circuit.
DTC P0140 or P0160

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-Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2
  1. Allow the engine to idle at operating temperature. Refer to Scan Tool Data List .
  2. Observe the affected HO2S 2 parameter using a scan tool.
  3. Clear the DTCs and record the Freeze Frame/Failure Records.
  4. Operate the engine at 2,000 RPM for at least 1 minute, then allow the engine to return to idle.
  5. Vary the engine speed from idle to 3,000 RPM several times within 5 seconds.
Does the voltage fluctuate above and below the specified range?		 400-520 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.
  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/Records.
Did the DTC fail this ignition?		 - Go to Step 4  Go to Intermittent Conditions
4
  1. Turn OFF the ignition.
  2. Disconnect the affected heated oxygen sensor (HO2S).
  3. Connect a 3-amp fused jumper wire between the HO2S high signal circuit on the engine harness side and a good ground.
  4. Turn ON the ignition, with the engine OFF.
  5. Observe the affected HO2S 2 parameter with a scan tool.
Is the voltage less than the specified value?		 25 mV Go to Step 5  Go to Step 6 
5
  1. Remove the jumper wire from the previous step.
  2. Connect a 3-amp fused jumper wire between the affected HO2S high signal circuit and the affected HO2S low signal circuit on the engine harness side of the engine control module (ECM) harness.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the affected HO2S 2 parameter with a scan tool.
Is the voltage less than the specified value?		 25 mV Go to Step 10  Go to Step 7 
6 Test the HO2S high signal circuit for an open or high resistance. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor (HO2S) Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 16  Go to Step 12 
7
IMPORTANT: The ECM has been damaged if the circuit was shorted to a voltage source.
Test the HO2S low signal circuit for a short to voltage. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor (HO2S) Wiring Repairs in Wiring Systems.Did you find and correct the condition?		 - Go to Step 15  Go to Step 8 
8 Test the affected HO2S low signal circuit for an open or high resistance. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor (HO2S) Wiring Repairs in Wiring Repairs.
Did you find and correct the condition?		 - Go to Step 16  Go to Step 9 
9  Test for continuity between the affected HO2S heater ignition 1 voltage circuit and the affected HO2S low signal circuit at the HO2S, sensor side.
Does continuity exist?		 - Go to Step 14  Go to Step 12 
10 Inspect for the following that may affect the HO2S operation:
    NOTE: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in Cautions and Notices.
  • HO2S contamination-Inspect the HO2S for contamination.
    • NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices.
  • Chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring
  • Exhaust system leaks or restrictions
  • Evaporative Emissions (EVAP) system malfunction-Inspect the EVAP control system. Refer to Inspection/Maintenance (I/M) Evaporative Emission (EVAP) System Set Procedure .
  • Incorrect fuel pressure-Refer to Fuel System Diagnosis .

Did you find and correct the condition?		 - Go to Step 16  Go to Step 11 
11 Test for an intermittent and for a poor connection at the affected HO2S. Refer to Testing for Intermittent Conditions and Poor Connections ,Connector Repairs , and Heated Oxygen Sensor (HO2S) Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 16  Go to Step 13 
12 Test for an intermittent and for a poor connection 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 16  Go to Step 15 
13 Replace the affected HO2S. Refer to Heated Oxygen Sensor (HO2S) Replacement Bank 1 Sensor 2 or Heated Oxygen Sensor (HO2S) Replacement Bank 2 Sensor 2 .
Did you complete the replacement?		 - Go to Step 16  -
14  Replace the affected HO2S. Refer to Heated Oxygen Sensor (HO2S) Replacement Bank 1 Sensor 2 or Heated Oxygen Sensor (HO2S) Replacement Bank 2 Sensor 2 .
Did you complete the replacement?		 - Go to Step 15  -
15 Replace the ECM. Refer to Engine Control Module (ECM) Replacement .
Did you complete the replacement?		 - Go to Step 16  -
16
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition.
  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 17  Go to Step 2 
17 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List System OK
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