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P1195

O2 Sensor 1/1 (Bank 1 Sensor 1) Slow During Catalyst Monitor.

  • Plymouth
  • Powertrain
  • Manufacturer code
  • Low severity

How this code is built

P
SystemPowertrain
1
Defined byThe manufacturer
1
AreaFuel and air metering
95
FaultThe specific fault in that area

What it means

On Plymouth, P1195 means the upstream oxygen sensor (Bank 1 Sensor 1, ahead of the catalyst) responded too slowly while the engine control unit was running its catalyst monitor test. The control unit judges the sensor's switching speed between rich and lean, and when it falls outside the expected limit it stores the code and usually lights the engine warning lamp.

Symptoms

  • Engine warning lamp on
  • Slightly higher fuel consumption
  • Rough or uneven idle in some cases
  • Mild hesitation or poor throttle response
  • Failed emissions test
  • Little or no change in how the car drives

Possible causes

  • Ageing or contaminated upstream oxygen sensor (Bank 1 Sensor 1) responding slowlylikely
  • Exhaust leak ahead of or near the upstream sensor letting in air and skewing readingspossible
  • Damaged wiring, poor connector contact or corrosion in the sensor circuitpossible
  • Sensor contamination from silicone, coolant, oil or fuel additivespossible
  • Fuelling fault such as a vacuum leak, fuel pressure problem or leaking injector causing abnormal mixture readingspossible
  • Engine control unit fault or outdated softwarerare

How to diagnose

  1. Read all stored and pending codes and note the freeze frame data, including engine temperature, load and fuel trims
  2. Check for related codes such as misfires, fuel trim, heater circuit or other oxygen sensor faults, and deal with those first
  3. Visually inspect the upstream sensor wiring and connector for chafing, heat damage, corrosion and water ingress
  4. Inspect the exhaust manifold, flange joints and pipework ahead of the sensor for leaks or blowing gaskets
  5. Check for vacuum leaks and review short and long term fuel trims at idle and at steady cruise
  6. With a scan tool, graph the upstream sensor voltage at operating temperature and check how quickly it switches between rich and lean
  7. Check the sensor heater circuit supply, earth and resistance against the manufacturer's specification for your model and engine
  8. Look for signs of contamination on the sensor tip and for oil or coolant consumption that could foul it

How to fix

  • Replace the upstream oxygen sensor if its response is confirmed slow, using the correct type for the engine
  • Repair any exhaust leak ahead of the sensor
  • Repair or replace damaged wiring and clean or renew faulty connectors
  • Fix vacuum leaks or fuelling faults that distort the mixture, and cure any oil or coolant ingress that contaminated the sensor
  • Apply any available manufacturer software update only if it is a documented fix for this code on your vehicle
  • After repair, clear the code and complete a drive cycle to confirm the monitor passes

Can I keep driving?

Low severity

The car can normally be driven while you arrange a repair, as this fault rarely affects safety. Do not leave it for long, as poor mixture control can raise fuel use and emissions and may mask other developing faults.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.

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