What Does P1137 Mean?
This code indicates the downstream heated oxygen sensor on Bank 1 (Sensor 2, after the catalytic converter) is not switching as expected and is stuck indicating a lean condition. The ECM monitors this sensor primarily for catalyst efficiency. A sensor that remains lean may indicate a deteriorating catalyst, an actual lean exhaust condition post-catalyst, or a sensor that has become biased or failed.
Common Causes
30%
Deteriorated catalytic converter on Bank 1 no longer storing oxygen properly
25%
Faulty downstream O2 sensor biased lean or with slow response
20%
Exhaust leak between the catalytic converter and the downstream sensor
15%
Upstream fuel system lean condition carrying through to the downstream sensor
10%
Downstream O2 sensor wiring issue or poor ground connection
Diagnostic Steps
1
Monitor the downstream O2 sensor voltage at steady cruise; it should remain relatively stable near 0.5-0.7V with a healthy catalyst.
2
Compare upstream and downstream O2 sensor waveforms; if the downstream mirrors the upstream switching pattern, the catalyst is failing.
3
Check for exhaust leaks between the catalytic converter outlet and the downstream sensor location.
4
Review Bank 1 upstream fuel trim data to ensure there is no persistent lean condition affecting exhaust composition.
5
Test the downstream O2 sensor response by inducing a brief rich condition (propane enrichment) and watching for voltage response.
Estimated Repair Cost
$100 - $1,200
Parts + labor, varies by vehicle and location
This code indicates the downstream heated oxygen sensor on Bank 1 (Sensor 2, after the catalytic converter) is not switching as expected and is stuck indicating a lean condition. The ECM monitors this sensor primarily for catalyst efficiency. A sensor that remains lean may indicate a deteriorating c...
The most common cause of P1137 (Lack of Downstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1) is: Deteriorated catalytic converter on Bank 1 no longer storing oxygen properly
Typical repair costs for P1137 range from $100 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
No direct safety hazard. A failed catalyst increases harmful emissions (HC, CO, NOx). If the catalyst substrate is breaking apart, fragments can cause exhaust restriction and potential engine damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1137 to identify the root cause.
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Powertrain
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Emissions / Catalyst Monitoring
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