What Chevy Code P0137 Means
Chevy code P0137 is a diagnostic trouble code that indicates the engine control module has detected low voltage from the downstream oxygen sensor on Bank 1, Sensor 2.
This sensor sits after the catalytic converter and helps the powertrain control module monitor exhaust efficiency, so a low-voltage signal can point to an electrical fault, exhaust issue, or a problem with the sensor itself.
If you are searching for how to fix Chevy code P0137, the key is to avoid guessing.
This code can be caused by a failed O2 sensor, wiring damage, exhaust leaks, or, less commonly, a catalytic converter issue, and the correct repair depends on which of those is actually present.
Common Symptoms of P0137 on Chevy Vehicles
Code P0137 does not always create severe drivability problems, but it can affect emissions monitoring and fuel control strategy.
In some cases, the vehicle may seem normal except for a check engine light.
- Check engine light illuminated
- Stored trouble code P0137
- Possible reduced fuel economy
- Failed emissions inspection
- Occasional rough idle or hesitation in related cases
On many Chevrolet models, the engine may continue to run well because the downstream oxygen sensor is mainly used to verify catalyst operation, not to directly control fueling like the upstream sensor does.
Most Common Causes of Chevy Code P0137
Before replacing parts, it helps to understand the most common causes.
Bank 1, Sensor 2 is the O2 sensor located after the catalytic converter on the side of the engine with cylinder number one.
A low-voltage reading usually means the sensor is not producing the expected signal or the PCM is not receiving it correctly.
1. Faulty downstream oxygen sensor
The most common cause is a worn or failed oxygen sensor.
Over time, contamination from oil, coolant, fuel additives, or age can slow the sensor response or keep the signal low.
2. Damaged wiring or connector
Heat from the exhaust, road debris, and corrosion can damage the harness or connector.
A broken signal wire, poor ground, or connector with bent terminals can trigger P0137 even if the sensor is still good.
3. Exhaust leak near the sensor
An exhaust leak before or near the downstream sensor can let outside air into the exhaust stream and affect voltage readings.
Even a small leak can create misleading sensor data.
4. Catalytic converter problems
A failing catalytic converter can change exhaust composition and sometimes cause abnormal downstream O2 sensor readings.
This is less common than a bad sensor, but it should be considered if the code returns after sensor replacement.
5. PCM or software issue
Rarely, the problem may involve the engine computer or an update-related calibration concern.
This is usually only pursued after the sensor, wiring, and exhaust system have been verified.
How to Diagnose Chevy Code P0137
The best approach is to inspect, test, and confirm before replacing anything.
A scan tool and a multimeter are usually enough for first-pass diagnosis.
Step 1: Check for other codes
Look for related codes such as P0136, P0138, P0140, or catalyst efficiency codes.
Multiple codes can point to a broader exhaust or electrical issue.
Step 2: Inspect the sensor and harness
Visually inspect Bank 1, Sensor 2, including the connector, wire routing, and exhaust area.
Look for melted insulation, chafed wiring, corrosion, loose terminals, or signs of exhaust leakage.
Step 3: Review live data
Use a scan tool to monitor the downstream O2 sensor voltage.
On many vehicles, the rear sensor should be relatively stable compared with the front sensor.
If it is stuck very low or shows no movement, that supports a P0137 diagnosis.
Step 4: Test the circuit
Check power, ground, and signal integrity with a multimeter according to the vehicle wiring diagram.
If the heater circuit is not operating correctly, the sensor may not reach proper temperature and may report low voltage.
Step 5: Inspect for exhaust leaks
Look at the exhaust manifold, pipe joints, gaskets, and catalytic converter connections.
A smoke test or careful cold-start inspection can reveal leaks that are hard to hear later when the exhaust gets hot.
Step 6: Compare sensor behavior
If possible, compare Bank 1, Sensor 2 to the opposite bank on V6 or V8 Chevy engines.
A significant difference can help confirm whether the issue is localized to one sensor or one exhaust path.
How to Fix Chevy Code P0137
Once you have identified the cause, the repair is usually straightforward.
The exact fix depends on what failed during diagnosis.
Replace the downstream oxygen sensor
If the sensor is slow, unresponsive, or stuck low and the wiring checks out, replacing the O2 sensor is often the correct repair.
Use the correct OE-equivalent part for your Chevrolet model, and make sure the threads are installed properly with anti-seize only if the manufacturer allows it.
Repair wiring or connector damage
If the harness is damaged, repair the affected wires with proper automotive-grade methods, such as solder and heat-shrink where appropriate, or approved crimp repairs.
Replace damaged connectors if terminals are loose or corroded.
Fix exhaust leaks
Repair leaking gaskets, cracked pipes, or damaged flex sections before clearing the code.
If air is entering the exhaust stream, the new sensor may not solve the problem.
Address catalytic converter issues
If the catalyst is degraded, replacement may be necessary.
This is more likely when P0137 appears with catalyst efficiency codes and live data shows abnormal downstream sensor behavior even after replacing the sensor.
Update software if needed
Some Chevrolet models may benefit from a PCM calibration update.
A dealer or qualified repair shop can check for Technical Service Bulletins related to oxygen sensor performance or false codes.
Can You Drive With Code P0137?
In many cases, yes, but it is not ideal to ignore the code for long.
The vehicle may continue to run normally, yet emissions performance can suffer and the underlying issue may worsen if the cause is wiring damage or an exhaust leak.
If the check engine light is flashing or the engine runs poorly, the problem should be diagnosed immediately.
DIY Repair Tips for Chevy Owners
If you plan to handle the repair yourself, a careful approach can save time and prevent repeat failures.
- Disconnect the battery only if required by your repair procedure
- Let the exhaust cool completely before working near the sensor
- Use the correct oxygen sensor socket or wrench
- Apply penetrating oil to stubborn sensors before removal
- Route the new harness away from hot exhaust components
- Clear the code and complete a drive cycle to verify the fix
How to Prevent P0137 From Returning
Prevention focuses on protecting the sensor and keeping the exhaust system sealed.
Routine inspection can reduce the chance of repeat failures, especially on older Chevy trucks, SUVs, and sedans that see winter road salt or high heat exposure.
- Inspect exhaust components during oil changes
- Repair misfires, oil consumption, or coolant leaks quickly
- Avoid aftermarket sealants that contaminate oxygen sensors
- Keep wiring secured away from exhaust heat
- Use quality replacement parts for sensors and connectors
Understanding how to fix Chevy code P0137 starts with identifying whether the low-voltage reading comes from the sensor, the wiring, or the exhaust system.
Once you confirm the root cause with live data and inspection, the repair is usually practical and cost-effective.