DTC P0131, P0132, P0137, P0138, P2A00, or P2A01. Saturn ION 2006

For 1990-2009 cars only

Makes 🢒 Saturn 🢒 2006 🢒 ION 🢒 Restraints 🢒 SIR 🢒 DTC P0131, P0132, P0137, P0138, P2A00, or P2A01

DTC Descriptors

DTC P0131: HO2S Circuit Low Voltage Sensor 1

DTC P0132: HO2S Circuit High Voltage Sensor 1

DTC P0137: HO2S Circuit Low Voltage Sensor 2

DTC P0138: HO2S Circuit High Voltage Sensor 2

DTC P2A00: HO2S Circuit Closed Loop (CL) Performance Sensor 1

DTC P2A01: HO2S Circuit Sensor 2

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Circuit	Short to Ground	High Resistance	Open	Short to Voltage	Signal Performance
HO2S High Signal	P0131, P0132, P0137, P0140, P1133, P2A00, P2A01	P0131, P0132, P0133, P0134, P0137, P0140, P1133, P2A00, P2A01	P0131, P0132, P0133, P0134, P0137, P0140, P1133, P2A00, P2A01	P0132, P0134, P0138, P0140, P1133, P2A00, P2A01	P0133, P0134, P0140, P1133, P2A00
HO2S Low Signal	P2A00, P2A01	P0131, P0132, P0133, P0134, P0138, P0140, P1133, P2A00, P2A01	P0131, P0132, P0133, P0134, P0138, P0140, P1133, P2A00, P2A01	P0134, P0138, P0140, P1133, P2A00, P2A01	P2A00

Typical Scan Tool Data

HO2S Sensor 1 Voltage

Circuit	Normal Range	Short to Ground	Open	Short to Voltage
HO2S High Signal	200-800 mV	0 mV	Approximately 470 mV	Approximately 1,100 mV
HO2S Low Signal	200-800 mV	455 mV	Approximately 450 mV	Approximately 445 mV

Circuit/System Description

Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The control module supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the control module operates in open loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and Closed Loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream; low HO2S voltage indicates a lean exhaust stream.

P2A01

The HO2S 2 is used for catalyst monitoring. This diagnostic runs once per ignition cycle. This diagnostic consists of two tests, a passive test and an intrusive test. During the passive test, if the HO2S 2 voltage transitions below 300 mV and above 650 mV, the DTC will pass for this ignition cycle. If the DTC does not pass during the passive test, the intrusive test will begin. During the intrusive test, the control module will force the air-to-fuel ratio rich and/or lean. The control module then waits for a predicted response from the HO2S 2. If the HO2S 2 voltage transitions below 300 mV and/or above 650 mV, the DTC will pass for this ignition cycle.

Conditions for Running the DTC

P0131 Lean Test Enable

•	DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.

•	The Loop Status parameter is Closed.

•	The Ignition 1 Signal parameter is between 10-18 volts.

•	The Fuel Level Sensor parameter is more than 10 percent.

•	The Throttle Position (TP) Indicated Angle parameter is between 15-50 percent.

•	DTC P0131 runs the lean test continuously when the above conditions are met for 2 seconds.

P0131 Power Enrichment Test Enable

•	DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.

•	The Ignition 1 Signal parameter is between 10-18 volts.

•	The Fuel Level Sensor parameter is more than 10 percent.

•	The Engine Run Time parameter is more than 30 seconds.

•	DTC P0131 runs the power enrichment test continuously when the above conditions are met for 2 seconds.

P0132 Rich Test Enable

•	DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.

•	The Loop Status parameter is Closed.

•	The Ignition 1 Signal parameter is between 10-18 volts.

•	The Fuel Level Sensor parameter is more than 10 percent.

•	The Throttle Position (TP) Sensor parameter is between 0-50 percent.

•	DTC P0132 runs the rich test continuously when the above conditions are met for 2 seconds.

P0132 Decel Fuel Cutoff Test Enable

•	DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.

•	The Loop Status parameter is Closed.

•	The Ignition 1 Signal parameter is between 10-18 volts.

•	The Fuel Level Sensor parameter is more than 10 percent.

•	The Engine Run Time parameter is more than 30 seconds.

•	DTC P0132 runs the decel fuel cutoff test continuously when the above conditions are met for 2 seconds.

P0137 Lean Test Enable

•	DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.

•	The Loop Status parameter is Closed.

•	The Ignition 1 Signal parameter is between 10-18 volts.

•	The Fuel Level Sensor parameter is more than 10 percent.

•	The TP Sensor parameter is between 15-50 percent.

•	DTC P0137 runs the lean test continuously when the above conditions are met for 2 seconds.

P0137 Power Enrichment Test Enable

•	DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.

•	The Loop Status parameter is Closed.

•	The Ignition 1 Signal parameter is between 10-18 volts.

•	The Fuel Level Sensor parameter is more than 10 percent.

•	The Engine Run Time parameter is more than 30 seconds.

•	The Power Enrichment parameter is active for more than 2 seconds.

•	DTC P0137 runs the power enrichment test during each occurrence of power enrichment, when the above conditions are met for 3 seconds.

P0138 Rich Test Enable

•	DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.

•	The Loop Status parameter is Closed.

•	The Ignition 1 Signal parameter is between 10-18 volts.

•	The Fuel Level Sensor parameter is more than 10 percent.

•	The TP Sensor parameter is between 0-50 percent.

•	DTC P0138 runs the rich test continuously when the above conditions are met for 2 seconds.

P0138 Decel Fuel Cutoff Test Enable

•	DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.

•	The Loop Status parameter is Closed.

•	The Ignition 1 Signal parameter is between 10-18 volts.

•	The Fuel Level Sensor parameter is more than 10 percent.

•	The Engine Run Time parameter is more than 30 seconds.

•	The decel fuel cut-off (DFCO) is active.

•	DTC P0138 runs the decel. fuel cutoff test during each occurrence of the decel. fuel cutoff, when the above conditions are met for 2 seconds.

P2A00

•	DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.

•	The Engine Run Time parameter is more than 100 seconds.

•	The Engine speed parameter is between 1,000-3,400 RPM.

•	The Ignition 1 Signal parameter is between 10-18 volts.

•	The Mass Airflow (MAF) Sensor parameter is between 10-30 g/s.

•	The ECT Sensor parameter is more than 70°C (158°F).

•	DTC P2A00 runs continuously when the above conditions are met for 5 seconds.

P2A01 Passive Test

•

DTCs P0030, P0036, P0053, P0054, P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1133, P1516, P2101, P2119, P2135, P2176, P2A00 are not set.

•	The engine is running.

•	The Engine Run Time parameter is less than 13.3 minutes.

•	DTC P2A01 runs the passive test once per drive cycle when the above conditions are met.

P2A01 Intrusive Test

•

•	The Engine Run Time parameter is more than 13.3 minutes.

•	The ignition 1 Signal parameter is between 10-18 volts.

•	The MAF sensor parameter is between 14-100 g/s.

•	The Engine Speed parameter is between 1,000-5,000 RPM.

•	The Vehicle Speed parameter is between 32-129 km/h (20-80 mph).

•	The Short Term FT parameter is between -20 and +20 percent.

•	The maximum number of intrusive attempts is less than 50.

•	DTC P2A01 runs the intrusive test once per drive cycle when the above conditions are met for 1 second.

Conditions for Setting the DTC

P0131 Lean Test

•	The control module detects that the HO2S 1 Voltage parameter is less than 50 mV.

•	DTC P0131 sets within 100 seconds during the lean test when the above condition is met.

P0131 Power Enrichment Test

•	The control module detects that the HO2S 1 Voltage parameter is less than 800 mV.

•	DTC P0131 sets within 100 seconds during the power enrichment test when the above condition is met.

P0132 Rich Test

•	The control module detects that the HO2S 1 parameter is more than 1,000 mV.

•	DTC P0132 sets within 15 seconds during the rich test when the above condition is met.

P0132 Decel Fuel Cutoff Test

•	The control module detects that the HO2S 1 parameter is more than 900 mV.

•	DTC P0132 sets within 10 seconds during the decel fuel cutoff test when the above condition is met.

P0137 Lean Test

•	The control module detects that the HO2S 2 voltage parameter is less than 50 mV.

•	DTC P0137 sets within 100 seconds during the lean test when the above condition is met.

P0137 Power Enrichment Test

•	The control module detects that the HO2S 2 voltage parameter is less than 550 mV and the HO2S 1 parameter is more than 800 mV.

•	DTC P0137 sets within 100 seconds during the power enrichment test when the above condition is met.

P0138 Rich Test

•	The control module detects that the HO2S 2 voltage parameter is more than 1,000 mV.

•	DTC P0138 sets within 100 seconds during the rich test when the above condition is met.

P0138 Decel Fuel Cutoff Test

•	The control module detects that the HO2S 2 voltage parameter is more than 900 mV.

•	DTC P0138 sets within 100 seconds during the decel fuel cutoff test when the above condition is met.

P2A00

•	The control module detects that the Loop Status parameter is open.

•	DTC P2A00 sets within 50 seconds when the above condition is met.

P2A01

The control module detects that the HO2S 2 did not transition below 300 mV and above 700 mV during the passive test.
One of the following tests fail:

Lean Intrusive Test

•	The control module detects that the HO2S 2 is more than 300 mV for 12 seconds.

•	The HO2S 1 is less than 350 mV.

Rich Intrusive Test

•	The control module detects that the HO2S 2 is less than 700 mV for 12 seconds.

•	The HO2S 1 is more than 600 mV.

DTC P2A01 sets within 7 minutes when the above conditions are met.

Action Taken When the DTC Sets

•	The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

•

The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

•	The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

•	A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

•	A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

•	Clear the MIL and the DTC with a scan tool.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

•	Engine Control Module Connector End Views

•	Engine Controls Connector End Views

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Scan Tool Reference

Scan Tool Data List

Circuit/System Verification

•	If any HO2S heater DTCs are set, perform those diagnostics first.

•	Allow the engine to reach operating temperature.

•	Engine running, observe the affected HO2S parameter with a scan tool.

-	The HO2S 1 value should vary from below 200 mV to above 800 mV and respond to fueling changes.

-	The HO2S 2 value should change more than 200 mV when the throttle is quickly cycled 3 times from closed to wide open and back to closed after running the engine at 1,500 RPM for 30 seconds.

•	The affected HO2S may be damaged due to contamination. Prior to replacing the affected HO2S, inspect for the following sources of contamination:

Notice: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in the Preface section.

-	A silicon contaminated HO2S

-	Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

-	Engine oil consumption--Refer to Oil Consumption Diagnosis .

-	Engine coolant consumption--Refer to Loss of Coolant .

Circuit/System Testing

Disconnect the affected HO2S.
Ignition ON, verify the applicable scan tool HO2S parameter is approximately 450 mV.

⇒	If more than the specified value, test the high signal circuit for a short to voltage. If the circuit tests normal, replace the control module.

⇒	If less than the specified value, test the high signal circuit for a short to ground. If the circuit tests normal, replace the control module.

Install a 3-amp fused jumper wire at the high signal circuit terminal. Toggle the jumper wire between the low signal circuit terminal and battery voltage. Verify the appropriate scan tool HO2S parameter toggles between 0 mV and approximately 1,000 mV.

⇒	If the appropriate scan tool HO2S parameter does not toggle correctly, test the low signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, test the high signal circuit for an open/high resistance. If the circuits test normal, replace the control module.

If all circuits test normal, replace the appropriate HO2S.

Repair Instructions

Notice: Refer to Heated Oxygen Sensor Resistance Learn Reset Notice in the Preface section.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Heated Oxygen Sensor 1 Replacement

•	Heated Oxygen Sensor 2 Replacement

•	Control Module References for powertrain control module (PCM) replacement, setup, and programming