Test Description

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

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.
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.

DTC P2231

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
2	Allow the engine to reach operating temperature. Observe the Loop Status Sensor 1 parameter with a scan tool. Does the scan tool display Closed Loop?	-	Go to Step 3	Go to Step 4
3	Observe the Freeze Frame/Failure Records for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. 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 or P0132 also set?	-	Go to Diagnostic Trouble Code (DTC) List - Vehicle	Go to Step 5
5	Turn OFF the ignition. Disconnect the heated oxygen sensor (HO2S) 1. Turn ON the ignition, with the engine OFF. 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 V	Go to Step 9	Go to Step 8
7	Turn OFF the ignition. Disconnect the engine control module (ECM) harness connectors. 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 11
8	Turn OFF the ignition. Disconnect the ECM harness connectors. 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 11
9	Test for shorted terminals and for poor connections at the HO2S. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?	-	Go to Step 14	Go to Step 12
10	Test for shorted terminals and for poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?	-	Go to Step 14	Go to Step 13
11	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 14	-
12	Replace the HO2S. Refer to Heated Oxygen Sensor 1 Replacement . Did you complete the replacement?	-	Go to Step 14	-
13	Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?	-	Go to Step 14	-
14	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. 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 15
15	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	System OK