DTC P0137 HO2S Circuit Low Voltage Sensor 2. Pontiac Sunfire 2000

For 1990-2009 cars only

Makes 🢒 Pontiac 🢒 2000 🢒 Sunfire 🢒 Engine 🢒 Engine Controls - 2.2L 🢒 DTC P0137 HO2S Circuit Low Voltage Sensor 2

Engine Controls Component Views
Power, Ground, and O2 Sensors
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice

Circuit Description

In order to control emissions, a catalytic converter converts any harmful exhaust emissions into harmless water vapor and carbon dioxide.

The Powertrain Control Module (PCM) has the capability to monitor this process by using a rear-heated oxygen sensor (HO2S 2). The HO2S 2 , located in the exhaust stream past the catalytic converter, produces an output signal which indicates the storage capacity of the catalyst. This in turn indicates the catalyst's ability to convert the exhaust emissions effectively. If the catalyst is functioning properly, the HO2S 2 signal will be far less active than the signal produced by the front oxygen sensor (O2S 1).

Replace the entire HO2S 2 assembly. Do not attempt to repair the HO2S 2 if the following conditions exist:

•	Damaged wiring

•	Damaged electrical connectors

•	Damaged terminals

Obstruction of the air reference and degraded HO2S 2 performance could result from any attempt to repair the above conditions.

The HO2S 2 must have a clean air reference in order for the HO2S 2 to function properly. This clean air reference is obtained by way of the HO2S 2 wires.

Conditions for Running the DTC

•	DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201, P0202, P0203, P0204, P0300, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set.

•	The air flow is more than 5.5 grams per second.

•	The engine coolant temperature (ECT) is more than 40°C (104°F).

•	The throttle position (TP) angle is between 5 percent and 50 percent for 4 seconds.

Conditions For Setting The DTC

The voltage reading on HO2S 2 remains below 43 mV for 150 seconds.

Action Taken When the DTC Sets

•	The malfunction indicator lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the malfunction present.

•	The PCM will record the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers.

•	A history DTC stores.

•	The coolant fan turns ON.

Conditions for Clearing the MIL/DTC

•	The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault.

•	A history DTC will clear after 40 consecutive warm-up cycles without a fault.

•	Use a scan tool to clear the DTCs.

Diagnostic Aids

•	The exhaust system -- Inspect the exhaust system for the following conditions:

-	Exhaust system leaks between the three-way catalytic converter and the flange

-	Exhaust system corrosion between the three-way catalytic converter and the flange

-	Exhaust system loose or missing hardware between the three-way catalytic converter and the flange

-	Repair the conditions as necessary.

•	A faulty electrical connection or a damaged harness -- Inspect the harness for a short to ground in the HO2S 2 signal circuit. Ensure that the HO2S 2 pigtail is not contacting the exhaust.

Check for the following conditions:

-	Wiring contacting the exhaust system

-	Improper mating

-	Broken locks

-	Improperly formed harness connectors

-	Damaged terminals

-	Faulty terminal-to-wire connections

-	A damaged harness

•	Intermittent test -- Observe the HO2S 2 on the scan tool while moving any of the related electrical connectors and the wiring harness with the ignition ON. If the malfunction is induced, the HO2S 2 display will change. This should help isolate the location of the malfunction.

An intermittent could be the result of the following conditions:

•	A faulty electrical connection

•	Rubbed-through wire insulation

•	A broken wire inside the insulation

Replace the entire HO2S 2 assembly. Do not attempt to repair the HO2S 2 if the following conditions exist:

•	Damaged wiring

•	Damaged electrical connectors

•	Damaged terminals

Obstruction of the air reference and degraded HO2S 2 performance could result from any attempt to repair the above conditions.

The HO2S 2 must have a clean air reference in order for the HO2S 2 to function properly. This clean air reference is obtained by way of the HO2S 2 wires.

Test Description

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

In order to determine if the engine is lean during power enrichment operate the vehicle under higher throttle/acceleration conditions while monitoring scan tool O2S voltage and the power enrichment parameter. A lean condition will cause O2S voltage to be less than 598 mV during power enrichment.

Monitor the O2S voltage of the opposite bank sensor. If the voltage activity of the opposite bank sensor is similar to the voltage activity of the suspect sensor check for lean conditions that would affect both cylinder banks. An opposite bank sensor with normal O2S voltage activity indicates the suspect O2S needs replacement or a lean condition exists only on the suspect O2S cylinder bank.

Step

Action

Value(s)

Yes

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Run the engine until the normal operating temperature is reached.
Using the scan tool, monitor the O2S voltage for the sensor that applies to this DTC.

Is the O2S voltage fixed less than the value specified?

26 mV

Go to Step 4

Go to Step 3

This DTC is intermittent.

Are any additional DTCs stored?

Go to Diagnostic Trouble Code (DTC) List/Type

Go to Diagnostic Aids

Turn OFF the ignition.
Disconnect the O2S connector for the sensor that applies to this DTC.
Jumper the O2S LOW circuit terminal on the engine harness side to a known good ground.
Turn ON the ignition, leaving the engine OFF.
Using the scan tool, monitor the O2S voltage for the sensor that applies to this DTC.

Is the O2S voltage within the specified value range?

351 - 551 mV

Go to Step 5

Go to Step 6

The O2S may be detecting a lean exhaust condition. Check for one of the following conditions:

•	O2S connector water intrusion

•	An exhaust leak between the O2S and the engine. Refer to Exhaust Leakage - Not OBD II in Engine Exhaust.

•	Vacuum leaks

•	Incorrect fuel pressure -- Refer to Fuel System Diagnosis .

•	Lean fuel injectors -- Refer to Fuel Injector Balance Test .

•	An inaccurate MAF sensor

Repair any of the above or similar engine conditions as necessary.

Did you find a problem?

Go to Step 10

Go to Step 8

Turn OFF the ignition.
Remove the jumper from the HO2S LOW circuit.
Disconnect the PCM that contains the HO2S HIGH signal circuit.
With a DMM measure and record the resistance between the HO2S HIGH signal circuit and ground.
Measure and record the resistance between the HO2S HIGH signal and the HO2S LOW circuit.

Is the resistance at the specified value for both tests?

∞

Go to Step 9

Go to Step 7

Repair the O2S signal HIGH circuit that shorted to ground or shorted to the O2S LOW circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 10

Replace the O2S. Refer to Heated Oxygen Sensor Replacement .

Is the action complete?

Go to Step 10

Important: The replacement PCM must be programmed.

Replace the PCM.

Refer to Powertrain Control Module Replacement .

Is the action complete?

Go to Step 10

Using the scan tool, clear the DTCs.
Start the engine.
Allow the engine to idle until the engine reaches the normal operating temperature.
Select DTC and the Specific DTC function.
Enter the DTC number which was set.
Operate the vehicle, with the Conditions for Setting this DTC, until the scan tool indicates the diagnostic Ran.

Does the scan tool indicate the diagnostic Passed?

Go to Step 11

Go to Step 2

Does the scan tool display any additional undiagnosed DTCs?

Go to Diagnostic Trouble Code (DTC) List/Type

System OK