P1137 — Lack Of HO2S Switch - Sensor Indicates Rich

For Ford vehicles

right downstream lambda sensor signal not changing sensor indicating lean mixture

powertrain (engine/transmission)

Is it safe to drive?

Short-term driving is OK You can usually drive for a while: the engine runs on a default fuel strategy, which costs you fuel and emissions. Fix it soon — prolonged driving with a bad O2 sensor can overheat and damage the catalytic converter.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm P1137 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the oxygen sensor circuit for damage, corrosion, chafing or poor contact.
Subsystem check Watch the sensor voltage in live data: a healthy upstream sensor switches rapidly between roughly 0.1 and 0.9 V.
Subsystem check Measure heater resistance on the sensor connector and check the heater fuse and relay.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P1137 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P1137 (parts and labor, USD, independent shop rates): Fix an exhaust leak near the sensor: $100–$300; Replace the oxygen sensor: $150–$450; Repair sensor wiring: $80–$250. Overall, fixing P1137 usually costs between $80 and $450. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

How much does it cost to fix P1137?

Fix an exhaust leak near the sensor — $100–$300; Replace the oxygen sensor — $150–$450; Repair sensor wiring — $80–$250. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

Is it safe to drive with P1137?

You can usually drive for a while: the engine runs on a default fuel strategy, which costs you fuel and emissions. Fix it soon — prolonged driving with a bad O2 sensor can overheat and damage the catalytic converter.

Will P1137 clear itself?

Sometimes P1137 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What is the most common cause of P1137?

The most common causes are: exhaust leak near the sensor, damaged sensor wiring or connector, oil or coolant contamination of the sensor tip.

How do I diagnose P1137 myself?

Start with a scan: confirm P1137, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the oxygen sensor circuit, and verify the suspect component against live data before buying parts.

A functioning oxygen sensor constantly informs your engine computer about exhaust gas composition so the fuel mixture can be adjusted on the fly. When that sensor stops reporting correctly, the control module logs a fault and switches to a backup fuel strategy. Code P1137 specifically indicates the upstream sensor on bank one is stuck in a "rich" signal — meaning the computer thinks there's too much fuel in the exhaust, even when there isn't. This isn't a sensor reading you'll want to ignore, because it throws off the entire fuel management system.

The engine control module relies on rapid voltage switching from the heated oxygen sensor to determine whether the air-fuel mixture is lean or rich. P1137 triggers when this sensor fails to switch properly and remains at high voltage, signaling rich conditions when the mixture may actually be balanced or even lean. The module stores a freeze frame snapshot alongside the fault code — capturing rpm, engine load, coolant temperature and vehicle speed at the moment the problem appeared. Reviewing that data first can point you directly at the cause instead of chasing unrelated issues.

The consequences of ignoring this code add up quickly. Your catalytic converter depends on a properly balanced exhaust stream to function efficiently. A faulty oxygen sensor feeding false rich signals eventually leads to excess fuel passing through the converter, which can cause overheating and premature failure. Catching and fixing P1137 early protects downstream components and keeps your fuel bill reasonable.

Common Symptoms of P1137

Check Engine Light illuminates on the dashboard
Noticeable increase in fuel consumption compared to normal driving
Rough or unstable engine idle
Sluggish or less responsive throttle behavior
Failed emissions testing at inspection time

What Causes P1137

Damaged wiring or corroded electrical connectors in the oxygen sensor circuit
Blown fuse protecting the sensor heater element
Exhaust leak positioned near the sensor location
Oil or coolant contamination coating the sensor's sensing tip
Faulty sensor internally (less common when external issues are present)

How to Diagnose P1137

Plug in an OBD2 scanner and pull the stored code. Confirm P1137 is present, then record the associated freeze frame data — this shows exactly what conditions existed when the fault occurred.
Look for any accompanying diagnostic trouble codes. Related codes often expose the root cause faster than testing the sensor directly. Also search for technical service bulletins specific to your vehicle make and model through the manufacturer website or nhtsa.gov.
Physically examine the wiring harness and connectors feeding the oxygen sensor. Look for broken insulation, corrosion buildup, pins pushed out of position, or wires rubbing against hot exhaust components.
Monitor live sensor voltage data with the scanner. A healthy upstream sensor fluctuates between roughly 0.1 volts and 0.9 volts several times per second. A stuck sensor shows flat or single-value readings.
Test the heater circuit resistance at the sensor connector and verify the heater fuse is intact. Replace any blown fuses and retest.
Clear the code and complete a drive cycle that recreates the freeze frame conditions. If P1137 returns, the problem has been confirmed and repairs are needed.

Repair Options and Costs

Begin with the least expensive possibilities before considering sensor replacement:

Exhaust leak near sensor: Repair or replace affected piping/gaskets — typically $100–$300
Sensor wiring damage: Strip, solder, and insulate damaged sections or replace the entire harness — typically $80–$250
Oxygen sensor replacement: Part and installation — typically $150–$450

Total repair cost for P1137 typically falls between $80 and $450 depending on which component actually failed. Accurate diagnosis before purchasing parts prevents spending more than necessary, since the most expensive repair is rarely the first one worth trying.

Can You Drive with P1137?

Short-term driving is possible because the engine control module substitutes a default fuel map when sensor data becomes unreliable. Expect reduced fuel economy and higher emissions during this time. Driving indefinitely with the fault active risks overloading the catalytic converter with unburned fuel, potentially causing expensive damage. Address the underlying cause promptly to restore normal operation and protect the exhaust system.