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Home >> Cadillac >> 2004 >> CTS Base, 3.2 N >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 21 (Engine Controls - 3.6L - Diagnosis (DTC P0008 - P0151)) >> Diagnosis >> DTC P0031, P0037, P0051, or P0057 >> 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. 4:  If both DTCs are set for either the front sensors or the rear sensors, the ignition voltage circuit to the heaters may be open. The front sensors are fused separately from the rear sensors.
  2. 5:  The heater control circuit is equipped with a feedback voltage. This feedback voltage allows the ECM to determine if the heater control circuit is open, shorted to ground, or shorted to a voltage. If the feedback voltage on the control circuit is not within the specified range, there is a condition internal to the ECM.
DTC P0031, DTC P0037, DTC P0051, or DTC P0057 - HO2S Heater Control Circuit Low Voltage

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. Start the engine.
  2. Allow the engine to idle for at least 30 seconds.
  3. Observe the DTC information with a scan tool.
Does DTC P0031, DTC P0037, DTC P0051, or DTC P0057 fail this ignition?		 - Go to Step 4  Go to Step 3 
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 Diagnostic Aids
4  Are DTCs P0031 and P0051 set at the same time or are DTCs P0037 and P0057 set at the same time? - Go to Step 7  Go to Step 5 
5 
  1. Turn OFF the ignition.
    2. IMPORTANT: The ignition must be OFF when disconnecting or connecting the heated oxygen sensor (HO2S) electrical connector.
  2. Disconnect the appropriate HO2S.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage between the heater control circuit of the HO2S and the engine control module (ECM) housing with a DMM.
Is the voltage within the specified range?		 4.6-5.2 V Go to Step 8  Go to Step 6 
6
  1. Turn OFF the ignition.
  2. Disconnect the ECM.
  3. Test the heater control circuit between the HO2S and the ECM for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 10  Go to Step 9 
7
    IMPORTANT: The ignition voltage circuit supplies voltage to other components. Make sure you test all circuits for a short to ground or test all components for being shorted that share the ignition voltage circuit.
  1. Repair the open or the grounded ignition 1 voltage circuit of the HO2S. Refer to Wiring Repairs in Wiring Systems.
  2. Replace the fuse if necessary.
Did you complete the repair?		 - Go to Step 10  -
8 Replace the HO2S. Refer to the appropriate procedure:
Did you complete the replacement?		 - Go to Step 10  -
9 Replace the ECM. Refer to Engine Control Module (ECM) Replacement .
Did you complete the replacement?		 - Go to Step 10  -
10
  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 11 
11 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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