01 Drivers Urged To Check Their Car Mirrors After Hidden Safet… • 02 P0012 A Camshaft Position - Timing Over Retarded (Bank 1) • 03 The Embarrassing Reason Some Drivers Keep Burning Through H… • 04 P0116 – Engine Coolant Temperature Range Fault: Causes and … • 05 Airbag Failure in Mahindra Scorpio Leads to Death in Accide… • 06 Why Your Car Suddenly Feels Slower Even Though Nothing Seem… • 07 P0034 Turbo charger bypass valve control circuit low • 08 Why Does My Car Go Faster Than the Speed Limit? • 09 How Airless Tires Can Change the Future of Driving • 10 Engine Sensors: How They Monitor and Optimize Performance •

DTC codes / BMW codes / P1193

P1193 · BMWPost-Catalyst Fuel Trim System Bank 2

P1193 on BMW vehicles indicates that the engine control module has detected an out-of-range fuel trim correction on bank 2 after the catalytic converter, meaning the post-catalyst oxygen sensor is reporting a mixture that the computer cannot bring back to stoichiometric using its normal fuel adjustments. The code is set when the long-term fuel trim for the post-catalyst monitoring circuit on bank 2 exceeds a calibrated threshold, typically because the sensor is slow, contaminated, or the converter is not storing oxygen properly.

SystemPowertrain
Code typeBMW specific
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • A slight decrease in fuel economy over time as the engine control module richens or leans the mixture
  • Occasional rough idle or hesitation when the engine is cold or under light load
  • A faint sulfur or rotten-egg smell from the exhaust if the converter is overheating
  • Failed emissions inspection due to elevated hydrocarbons or carbon monoxide
  • In rare cases, a slight surge or stumble during steady-speed cruising

Common causes, most likely first

  1. Aged or contaminated post-catalyst oxygen sensor on bank 2 that responds slowly or has drifted in calibration
  2. Exhaust leaks between the bank 2 catalytic converter and the post-catalyst oxygen sensor, allowing outside air to skew the reading
  3. A failing bank 2 catalytic converter that no longer stores and releases oxygen properly, causing the post-catalyst sensor to see a lean or rich bias
  4. Oil or coolant consumption from worn valve guides or a failing head gasket contaminating the post-catalyst sensor
  5. A leaking fuel injector on bank 2 that creates an excessively rich mixture the converter cannot fully process
  6. A restricted or failed positive crankcase ventilation valve that introduces unmetered air or oil vapor into bank 2
  7. Wiring damage or corrosion at the bank 2 post-catalyst oxygen sensor connector causing an intermittent signal

How to diagnose and fix it

  1. Connect a scan tool and record freeze-frame data for P1193, then check for any stored or pending codes that might indicate a related misfire or mixture fault.
  2. Visually inspect the bank 2 exhaust system from the manifold to the post-catalyst sensor for leaks, loose clamps, or cracked pipes, and repair any leaks before proceeding.
  3. Graph the bank 2 post-catalyst oxygen sensor voltage on a scan tool while holding the engine at 2500 rpm; a healthy sensor should switch rapidly between 0.1 and 0.9 volts, while a lazy or flat-lined sensor indicates replacement.
  4. Perform a propane enrichment test at the intake to confirm that the pre-catalyst fuel trims respond correctly and that the post-catalyst sensor reacts to the change.
  5. Check the bank 2 post-catalyst oxygen sensor heater circuit resistance and compare it to the manufacturer's specification, replacing the sensor if the heater is open or shorted.
  6. Measure exhaust backpressure before and after the bank 2 catalytic converter using a pressure gauge; a reading above 1.5 psi at idle suggests a restricted or failed converter.
  7. If the sensor and exhaust are good but the post-catalyst trim remains out of range, perform a catalytic converter efficiency test by comparing the switching frequency of the pre- and post-catalyst sensors, and replace the bank 2 converter if efficiency is below specification.

What the post-catalyst fuel trim really tells you

  • A post-catalyst fuel trim code is often caused by a lazy oxygen sensor rather than a failed catalytic converter, so always graph the sensor response before condemning the converter.
  • Exhaust leaks downstream of the pre-catalyst sensor but upstream of the post-catalyst sensor can pull in outside air and make the post-catalyst sensor report a false lean condition, setting P1193 even when the converter is healthy.
  • On many BMW engines, oil consumption from worn valve stem seals contaminates the post-catalyst sensor over time, causing a slow response that eventually triggers P1193 without any driveability complaint.
  • The post-catalyst fuel trim is a monitoring strategy, not a primary mixture control; a significant deviation here often points to a converter that has lost its oxygen storage capacity rather than a base engine mixture problem.
  • Replacing the post-catalyst oxygen sensor without checking for exhaust leaks or crankcase ventilation faults frequently leads to a repeat code within a few thousand miles.

Can I keep driving with P1193?

You can generally continue driving with P1193 because the engine management system still maintains a safe mixture, but avoid prolonged heavy acceleration or towing until the fault is diagnosed. Have the vehicle inspected soon, especially if you notice rough running or a drop in fuel economy, to prevent damage to the catalytic converter.

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 BMW vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage