1. How do I fix error code P0137?

Start by checking live data and inspecting Bank 1 Sensor 2 wiring and the exhaust for leaks. Repair harness or connector faults first, then replace the downstream O2 sensor only if the signal is confirmed faulty.

2. Is it safe to drive with a P0137 code?

Usually yes for short trips if the car runs normally and the Check Engine Light is steady. If you have a flashing CEL, misfires, or a strong exhaust smell, stop driving and diagnose it.

3. Why is my O2 sensor getting low voltage?

Common causes include a failing oxygen sensor, an open circuit, a short to ground, poor ground, heater circuit faults, or an exhaust leak upstream of the sensor. Each of those can pull the reported voltage low even when the catalytic converter is not the primary fault.

4. How much does it cost to fix a P0137 code?

Most P0137 repairs cost $150 to $300 at an independent garage. If it's a wiring fault, expect $80 to $150. Catalytic converter replacement costs $400 to $1,200 — but P0137 alone does not confirm converter failure.

P0137 Code Repair Cost: O2 Sensor Fix, Causes and VAG Guide

The P0137 code typically costs $150 to $300 to fix at an independent garage when the downstream O2 sensor needs replacing. If the fault is a wiring issue or exhaust leak, the repair can cost as little as $50 to $150. Only if the catalytic converter is genuinely damaged does the cost rise to $400 to $1,200 — but P0137 alone does not confirm converter failure.The Check Engine Light that pops up unexpectedly causes vehicle owners to rush to part catalogues rather than get their vehicles diagnosed. If you have the P0137 code, this approach can prove to be hazardous since the code suggests the existence of a low voltage reading for the downstream oxygen sensor but not necessarily a faulty catalytic converter or oxygen sensor itself. This article covers everything about the P0137 code, Bank 1 Sensor 2 identification and testing.

Table of Contents

What the P0137 Code Means

Fault code P0137 is an indication that the engine computer (ECM/PCM) of your car has received a low voltage output from the Bank 1 Sensor 2 sensor for more time than normal. The Bank 1 Sensor 2 sensor is referred to as the downstream oxygen sensor because it is located behind the catalytic converter. The primary function of this sensor is to determine how well the catalytic converter works rather than adjust the fuel mixture of your vehicle.The term Bank 1 refers to the bank of cylinders in which cylinder one is mounted. However, there is no Bank 2 in single bank engines. This information helps avoid costly order errors.

What Does It Cost to Fix P0137 Code?

P0137 — Estimated Repair Costs (USD)

Repair Type	DIY Cost	Workshop Cost	Notes
Downstream O2 sensor parts only	$20 – $80	—	Bosch, Denso or NGK recommended for VAG engines
O2 sensor replacement labour, independent garage	—	$150 – $300	Most common total repair cost for P0137
O2 sensor replacement labour, dealership	—	$250 – $450	Higher labour rate applies at franchise dealers
Wiring harness repair	$10 – $30	$80 – $150	Often cheaper than a new sensor — check this first
Exhaust leak repair	$20 – $60	$50 – $200	Gasket or flex pipe depending on location
Catalytic converter replacement check first	$150 – $400 parts only	$400 – $1,200	Only if genuinely failed. P0137 alone does not confirm converter failure

DIY cost = parts only, no labour

Workshop cost = parts + labour estimate

The most important number here: P0137 by itself does not mean your catalytic converter needs replacing. Diagnosing the actual fault first saves most people $300 to $900.

Common Symptoms and What You Will Notice

The Check Engine Light is the most common symptom, and many cars still drive completely normally because the downstream O2 sensor is not the main sensor used for fuel control. Your car can feel fine while still failing an emissions test or leaving readiness monitors incomplete.

Some drivers notice a small drop in fuel economy. Some vehicles log related codes depending on the manufacturer. If you want to check any other stored codes, TheCarLane has an OBD2 fault code lookup tool that helps you place individual faults in a proper diagnostic sequence.

Is It Safe to Drive With P0137 Code?

Short-term driving is normally okay if the engine is running fine, the CEL is stable, and there is no distinct exhaust odor. The real threat lies in increased pollution, potential failure to pass inspections, and lost clues should any additional trouble arise from an existing minor exhaust issue or faulty wiring.In cases where misfire occurs, a blinking CEL is present, the catalyst overheats, and a gasoline smell is detectable, cease driving and conduct diagnosis immediately. These problems indicate an existing problem that would harm the catalytic converter much sooner than the P0137 code alone.

What Causes Low Voltage on the Downstream O2 Sensor

A worn or failed downstream O2 sensor is the most common cause, especially when age or contamination reduces signal quality over time. But low voltage can also come from:

An open circuit in the wiring
A short to ground
A poor earth connection
Heat-damaged wiring near the exhaust pipe
An exhaust leak upstream of the sensor pulling extra oxygen into the exhaust stream

Engine problems like air leaks, fuel delivery faults, or misfires can also affect exhaust oxygen levels enough to make diagnosis confusing. Treat P0137 as a system clue, not a parts verdict.

Sensor vs Wiring vs Exhaust Leak: Quick Differentiators

Bad sensor: Shows a flatline reading or a signal that does not react when engine load changes.

Wiring fault: Appears and disappears intermittently, especially when the car moves or vibrates, because a loose pin or corroded connector changes the circuit path.

Exhaust leak: Leaves soot marks and produces a ticking noise near a joint or flange. When the downstream sensor reads lean but everything else looks normal, an exhaust leak becomes a stronger suspect than the sensor itself.

Step-by-Step Diagnosis (Do This Before Replacing Parts)

Use a scan tool/OBD2 scanner to document stored, pending, and freeze frame data like coolant temperature, RPM, engine load, and speed. The freeze frame information indicates what kind of operating condition caused the malfunction, and in many cases, it is the key factor that distinguishes a malfunction when the sensor is still getting warmed up from one where it operates fully warmed up.Next, check the live data of Bank 1 Sensor 2 at idle and when held at 2,000 – 2,500 RPMs, then check the connector, wiring harness routing, and exhaust joints. If possible, test the heater circuit and reference/ground circuits because without a functional heater circuit, a sensor will not be able to generate a reliable voltage signal.

Live Data: What Normal Downstream Voltage Looks Like

The upstream sensor (Sensor 1) switches rapidly as the engine computer adjusts fuelling. The downstream sensor (Sensor 2) should look much slower and steadier when the catalytic converter is working properly. A signal stuck below 0.1 volts is a strong warning sign — a healthy post-catalyst sensor should show some movement above that level, not a dead flatline.

Simple Tests to Narrow It Down

Wiggle test: Gently move the wiring harness and connector while watching live data. If the voltage changes sharply when you move the wiring, the fault is in the circuit, not the exhaust stream.

Exhaust leak check: Listen for a ticking sound and look for soot marks around the exhaust manifold, flex pipe, and catalytic converter flange. A leak upstream of the sensor creates low-voltage readings that look exactly like sensor failure.

Avoid the Biggest Misdiagnosis: P0137 vs P0420

P0137 and P0420 both involve the post-catalyst monitoring system but mean very different things. P0137 is a low-voltage signal problem. P0420 means the catalytic converter’s efficiency has dropped below the acceptable level.

Confusing the two is an expensive mistake. A weak downstream sensor can make a healthy converter look like it is failing. A genuinely failing converter can create patterns that look like sensor failure. The only reliable separator is live data — the switching behaviour of the downstream sensor shows whether the problem is electrical or a true loss of catalyst performance.

If you are seeing both codes together, start with P0137 first. Resolving the signal fault often clarifies whether P0420 is a real catalyst issue or a false reading caused by an unreliable sensor.

TheCarLane Note: 1.0 TSI (3-Cylinder) Reality Check

On a 1.0 TSI three-cylinder engine there is only one bank, so P0137 always refers to Bank 1 Sensor 2 after the single catalytic converter. A useful pattern to know: a steady 0.1 to 0.2 volts at idle can be completely normal on this setup. But a flatline below 0.1 volts in Car Scanner that does not respond at all to throttle changes is more consistent with genuine sensor failure rather than a wiring or exhaust issue.

DIY vs Garage: Which Repairs Can You Do Yourself?

Repair	DIY Friendly?	Skill Level
OBD2 scanning and live data check	Yes	Beginner
Visual wiring and connector inspection	Yes	Beginner
Exhaust leak check	Yes	Beginner
Downstream O2 sensor replacement	Yes with basic tools	Intermediate
Wiring harness repair	Depends on damage location	Intermediate
Catalytic converter diagnosis	Garage recommended	Advanced
Catalytic converter replacement	Garage recommended	Advanced

The wiring inspection, exhaust leak check, and OBD2 scanning are all DIY-friendly and should be done before spending anything. The sensor replacement itself is a straightforward job on most VAG engines with basic tools — the sensor is accessible and the procedure is well documented. Catalytic converter diagnosis and replacement should involve a garage because misdiagnosis at that stage is costly.

Fix Options and What Usually Solves It

Fix any damage to wiring harness, any poorly fitting pins, and any corrosion in the connectors prior to clearing the codes because electrical failures can generate exactly the same low voltage the ECM thinks it’s getting. Take care of any exhaust leaks before the downstream oxygen sensor because of potential for a quick recurrence and possible failure of the new sensor.Remove the downstream O2 sensor only if the signal itself is faulty, which could be caused by wiring or grounding problems, exhaust leaks, or the signal from another problem component pulling it down. If the catalytic converter is inefficient, fix the underlying issue causing it to run that way, like oil burning or frequent misfires.

After the Repair: Clearing Codes and Verifying the Fix

Clear the codes, complete a proper drive cycle, and confirm no pending codes return. The repair is not verified until the system’s self-tests have run and passed under normal driving conditions — the absence of a Check Engine Light in the first few minutes does not confirm a fix.

After the drive cycle, recheck live data and look for stable downstream voltage. A repaired system should no longer show a persistent low flatline.

Ayush Sondhi

Founder of TheCarLane | Automotive Enthusiast
Ayush shares practical automotive knowledge based on real-world ownership and hands-on experience. His work focuses on diagnostics, engine systems, common car problems, and clear explanations that help everyday drivers understand their vehicles better.

P0137 Code Repair Cost: Causes, O2 Sensor Fix and VAG Diagnosis Guide