Test Description

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

2: When the system is operating correctly, the HO2S 1 voltage should toggle above and below the bias voltage. You may need to operate the vehicle within the Freeze Frame conditions and Conditions for Setting the DTC in order to duplicate the malfunction that was detected by the PCM.
4: The specified value is what is measured on a correctly operating system.

DTC P1171

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics
1	Did you perform the Diagnostic System Check - Vehicle?	-	Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Operate the engine at normal operating temperature. Operate the engine above 1,200 RPM for 2 minutes. Observe the HO2S 1 voltage parameter with a scan tool. Does the scan tool indicate that the heated oxygen sensor (HO2S) 1 voltage is less than the specified values?	300 mV	Go to Step 4	Go to Step 3
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	Turn OFF the ignition. Disconnect the HO2S sensor. Turn ON the ignition, with the engine OFF. Measure the voltage from the HO2S 1 high signal circuit on the powertrain control module (PCM) side of the harness connector to a good ground with the DMM. Does the voltage measure within the specified range?	350-550 mV	Go to Step 6	Go to Step 5
5	Test the HO2S 1 high signal circuit for a short to ground or a short to the HO2S 1 low signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 11	Go to Step 8
6	The HO2S 1 is detecting a lean condition or may be contaminated. Inspect for the following conditions: HO2S connector water intrusion Silicon-contaminated HO2S An exhaust leak between the HO2S 1 and the engine-Refer to Exhaust Leakage in Engine Exhaust. Vacuum leaks Incorrect fuel pressure-Refer to Fuel System Diagnosis . Lean fuel injectors-Refer to Fuel Injector Balance Test with Tech 2 . Repair any of the above or similar engine conditions as necessary. Did you find and correct the condition?	-	Go to Step 11	Go to Step 7
7	Inspect for poor connections at the harness connector of the HO2S 1 sensor. 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 11	Go to Step 9
8	Inspect for poor connections at the harness connector of the 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 11	Go to Step 10
9	IMPORTANT: Before replacing the HO2S determine and remove any source of contamination. Replace the HO2S 1. 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 11	-
10	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 11	-
11	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 12
12	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