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Home >> Cadillac >> 2004 >> CTS Base, 3.2 N >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 24 (Engine Controls - 3.6L - Diagnosis (DTC P2188 - P2636)) >> Engine Controls Diagnosis >> DTC P2231 or P2234 >> 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. 2:  This step determines if the condition exists. If there is a condition with the HO2S circuits, the ECM commands open loop for the applicable sensor.
  2. 5:  This step tests for a bias voltage across the reference voltage circuit and the low reference circuit of the HO2S. The bias voltage that you are measuring, is the voltage difference between the reference voltage circuit and the low reference circuit. If the reference voltage circuit or the low reference circuit of the HO2S is shorted to a voltage, the bias voltage will be more than the specified value, which indicates there is a condition with the circuits.
  3. 11:  A rich or lean fuel injector can cause this DTC to set. Perform the Fuel Injector Balance Test with Special Tool to verify that the fuel injectors are delivering fuel equally. Replace any fuel injector that has a fuel pressure drop, or resistance measurement, that is not consistent in comparison to the other fuel injectors. Refer to Fuel Injector Balance Test with Special Tool .
DTC P2231 or P2234

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 
IMPORTANT: DTC P2231 is for bank 1 sensor 1 and DTC P2234 is for bank 2 sensor 1.
  1. Allow the engine to reach operating temperature.
  2. Observe the Loop Status Bn. 1 Sen. 1 or Loop Status Bn. 2 Sen. 1 with a scan tool.
Does the scan tool display Closed Loop?		 - 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 Diagnostic Aids
4 Is DTC P0131, P0132, P0151, or P0152 also set? - Go to Diagnostic Trouble Code (DTC) List Go to Step 5 
5 
  1. Turn OFF the ignition.
  2. Disconnect the appropriate heated oxygen sensor (HO2S).
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage between the reference voltage circuit and the low reference circuit of the HO2S with a DMM.
Is the voltage within the specified range?		 350-550 mV Go to Step 6  Go to Step 7 
6 Measure the voltage between the input pump current circuit and a good ground with a DMM.
Is the voltage less than the specified value?		 1.0 V Go to Step 9  Go to Step 8 
7
  1. Turn OFF the ignition.
  2. Disconnect the engine control module (ECM) harness connectors.
  3. Measure the resistance between the reference voltage circuit and the heater control circuit of the HO2S with a DMM.
Is OL displayed on the DMM?		 - Go to Step 10  Go to Step 12 
8
  1. Turn OFF the ignition.
  2. Disconnect the ECM harness connectors.
  3. Measure the resistance between the input pump current circuit and the heater control circuit of the HO2S with a DMM.
Is OL displayed on the DMM?		 - Go to Step 10  Go to Step 12 
9 Test for shorted terminals and for poor connections 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 15  Go to Step 11 
10 Test for shorted terminals and for 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 
11 
  1. Turn OFF the ignition.
  2. Connect the HO2S.
  3. Perform the Fuel Injector Balance Test with Special Tool .
  4. Return to this diagnostic after you have completed the procedure.
Did you find and correct the condition?		 - Go to Step 15  Go to Step 13 
12 Repair the reference voltage circuit or the input pump current circuit of the HO2S for being shorted to the heater control circuit.
Did you complete the repair?		 - Go to Step 15  -
13 Replace the HO2S. Refer to the appropriate procedure:
Did you complete the replacement?		 - Go to Step 15  -
14 Replace the ECM. Refer to Engine Control Module (ECM) Replacement .
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 System OK
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