A contaminated or aged upstream oxygen sensor that has drifted rich and no longer responds accurately.; A leaking or stuck-open fuel injector on bank 1 delivering excess fuel.; Excessive fuel pressure from a failed fuel pressure regulator or a restricted fuel return line.; A faulty engine coolant temperature sensor reporting a cold engine so the PCM commands extra fuel.; A dirty or failing mass airflow sensor over-reporting incoming air and causing rich fuel trim.; A leaking intake manifold gasket or injector O-ring that lets unmetered fuel vapor into the intake.; A PCM calibration issue or wiring fault in the HO2S signal circuit that skews the sensor reading.

DTC codes / Chrysler codes / P1136

P1136 · ChryslerHO2S Rich Average Bank 1 Sensor 1

Q: What does code P1136 mean?

HO2S Rich Average Bank 1 Sensor 1. P1136 on a Chrysler vehicle means the powertrain control module has calculated that the upstream oxygen sensor on bank 1 is reporting a fuel mixture that stays too rich on average over its monitoring period. The computer is not flagging a single lean or rich spike; it is comparing the sensor's long-term average against the rich threshold and storing the code when that average stays beyond the limit.

P1136 on a Chrysler vehicle means the powertrain control module has calculated that the upstream oxygen sensor on bank 1 is reporting a fuel mixture that stays too rich on average over its monitoring period. The computer is not flagging a single lean or rich spike; it is comparing the sensor's long-term average against the rich threshold and storing the code when that average stays beyond the limit.

SystemPowertrain

Code typeChrysler specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Symptoms you may notice

Illumination of the check engine light, often with no other symptoms the driver can feel.
A noticeable drop in fuel economy as the engine runs richer than commanded.
Black sooty exhaust smoke or a strong fuel smell at the tailpipe in more advanced cases.
Rough idle, surging, or hesitation when accelerating from a stop.
Elevated hydrocarbon emissions that may fail an emissions inspection.
In severe cases, spark plug fouling and misfire symptoms as excess fuel washes the cylinders.

Common causes, most likely first

A contaminated or aged upstream oxygen sensor that has drifted rich and no longer responds accurately.
A leaking or stuck-open fuel injector on bank 1 delivering excess fuel.
Excessive fuel pressure from a failed fuel pressure regulator or a restricted fuel return line.
A faulty engine coolant temperature sensor reporting a cold engine so the PCM commands extra fuel.
A dirty or failing mass airflow sensor over-reporting incoming air and causing rich fuel trim.
A leaking intake manifold gasket or injector O-ring that lets unmetered fuel vapor into the intake.
A PCM calibration issue or wiring fault in the HO2S signal circuit that skews the sensor reading.

How to diagnose and fix it

Connect a scan tool and record live fuel trim data, HO2S voltage, coolant temperature, and mass airflow readings to confirm the rich average before touching parts.
Inspect the upstream oxygen sensor wiring and connector for chafing, corrosion, or oil contamination that could distort the signal.
Check fuel pressure with a gauge against the Chrysler specification and look for a regulator that holds pressure too high.
Perform an injector balance or leak-down test to identify a sticking or leaking injector on bank 1.
Verify engine coolant temperature sensor readings against actual engine temperature with an infrared thermometer.
Clean or test the mass airflow sensor and compare its reported airflow to expected values at idle and cruise.
Replace the upstream HO2S only after the fuel delivery and air metering systems have been ruled out, then clear the code and verify fuel trim returns to normal.

Why the oxygen sensor is often not the culprit

A rich average code frequently traces back to a leaking injector or high fuel pressure rather than a failed sensor, so replacing the HO2S first often leaves the code returning within a few drive cycles.
Chrysler PCMs on some models will set P1136 when the coolant temperature sensor reads colder than actual, because the computer enriches the mixture based on that false cold signal.
Oil or coolant contamination from a failing head gasket can coat the oxygen sensor and bias its average rich without any sensor circuit fault, so check for contamination before condemning the sensor.
A dirty mass airflow sensor that over-reports airflow will drive rich fuel trim on bank 1 and can set P1136 even though the sensor itself has no electrical fault.
Short-trip driving and a stuck-open thermostat can keep the engine in open-loop enrichment long enough to skew the HO2S average and trigger this code intermittently.

Can I keep driving with P1136?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy acceleration and long trips because continued rich operation can foul spark plugs and damage the catalytic converter. If the check engine light begins flashing or you notice misfiring, stop driving and have the vehicle towed.

Tools that help

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Guidance is general and written for Chrysler vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.