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DTC codes / Chrysler codes / P1195

P1195 · ChryslerO2 Sensor 1/1 (Bank 1 Sensor 1) Slow During Catalyst Monitor

P1195 on Chrysler vehicles means the powertrain control module (PCM) saw the upstream oxygen sensor on bank 1, sensor 1 respond too slowly during the catalyst monitor test. The PCM commands a rich-to-lean fuel swing and expects the sensor voltage to cross its threshold within a set time, but the signal lags, so the monitor fails and the code is stored.

SystemPowertrain
Code typeChrysler specific
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering

Symptoms you may notice

  • Malfunction indicator lamp (MIL) illuminated, often with no other symptoms besides the warning light
  • Slightly rough idle or hesitation during light acceleration
  • Poor fuel economy as the PCM struggles to correct a lazy sensor signal
  • Occasional stumble or surge when the engine transitions from rich to lean
  • Failed emissions test due to incomplete or failed catalyst monitor
  • In rare cases, a slight sulfur or rotten-egg smell from the exhaust

Common causes, most likely first

  1. Aged or contaminated upstream oxygen sensor (bank 1 sensor 1) that responds sluggishly
  2. Exhaust leak ahead of the sensor, allowing outside air to dilute the sample
  3. Wiring damage or corrosion at the sensor connector or PCM pins
  4. A lazy sensor caused by oil or coolant contamination from an internal engine leak
  5. Restricted fuel delivery or a weak fuel pump that skews the rich-lean swing
  6. A failing catalytic converter that masks the sensor's true response during the monitor
  7. PCM software calibration issue or a faulty PCM driver circuit

How to diagnose and fix it

  1. Inspect the bank 1 sensor 1 wiring and connector for chafing, corrosion, or loose pins
  2. Check for exhaust leaks between the engine and the upstream sensor using a smoke test
  3. Verify fuel pressure and fuel trim readings with a scan tool to rule out delivery issues
  4. Use a scan tool to watch the upstream oxygen sensor voltage switching rate; a lazy sensor stays flat or crosses slowly
  5. Perform a propane enrichment test to confirm the sensor reacts to a known rich condition
  6. Replace the bank 1 sensor 1 oxygen sensor with the correct Chrysler-specified part
  7. Clear the code and run the catalyst monitor to confirm the repair

Why a slow O2 sensor fools many technicians

  • A lazy upstream sensor often passes a simple voltage swing test but still fails the faster catalyst monitor, so watching live data alone can mislead you.
  • Exhaust leaks upstream of the sensor are a common cause that mimics a bad sensor, and replacing the sensor without fixing the leak will bring the code back.
  • Fuel contamination from a failing fuel pressure regulator or leaking injector can coat the sensor and slow its response, so check fuel trims before condemning the sensor.
  • On some Chrysler models, a weak battery or poor ground can cause the PCM to misread sensor response during the monitor, so verify powers and grounds first.
  • The code does not always mean the catalytic converter is failing; the catalyst monitor uses the upstream sensor to judge converter efficiency, and a slow sensor can falsely implicate the converter.

Can I keep driving with P1195?

You can usually keep driving with P1195, but avoid long trips and heavy loads until it is diagnosed because a lazy sensor can worsen fuel economy and emissions. If the engine begins to misfire or run rough, stop driving and have it checked promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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

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