I recently replaced both Bank 1 and Bank 2 oxygen sensors on my Ford Expedition, but the P2196 diagnostic code is still appearing. The vehicle now shows a rich fuel mixture condition. What other potential causes could be responsible for this persistent error? I've checked the spark plugs and they are dry and in good condition. Any guidance on further diagnostics would be greatly appreciated.
The spark plugs are dry and were last serviced about nine months ago. The ignition coils were replaced last week. Now I'm noticing white smoke coming from the exhaust with a strong gasoline odor. This suggests possible fuel system issues. I’ll have to wait for my friend to bring his fuel pressure gauges, as I don’t currently own any. Any additional troubleshooting steps would be very helpful.
Use an OBD2 scanner to check Fuel Trim (FT), B1S1 oxygen sensor voltage, and ECT readings. If these values are abnormal, it may point to a fuel delivery issue. Also consider performing a fuel pressure leak-down test during KOEO. Check for any P030x misfire codes — their presence could indicate underlying combustion problems.
No other diagnostic trouble codes are present. Could the Mass Air Flow (MAF) sensor be faulty? If fuel pressure is low, what might be causing that issue? A clogged or malfunctioning MAF could lead to incorrect air-fuel ratio calculations and result in a rich condition.
Agreed with previous post — clean the Mass Air Flow (MAF) sensor and avoid using an oiled air filter. Perform a fuel pressure test, then conduct a KOEO fuel pressure leak-down check to assess for leaks or drops in pressure that may indicate injector or pump issues.
The oxygen sensor is just a messenger — don't blame it first. The P2196 code indicates the engine is running too rich, with Bank 1 Sensor 1 (B1S1) O2 sensor voltages remaining high and failing to fluctuate properly. Use an OBD2 scanner to monitor B1S1 voltage, fuel trim values, and engine temperature (ECT). A sticking fuel injector is a likely culprit. Perform a fuel pressure test, then conduct a KOEO (Key On, Engine Off) leak-down check. Also inspect Bank 1 spark plugs — any wet or blackened ones may indicate excessive fuel delivery. Additionally, clean the Mass Air Flow (MAF) sensor and ensure you're not using an oiled air filter.