What does it mean?
P1198 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: O2 Sensor Heater Circuit (Bank 1-Sensor 2) Electrical Malfunction .
Symptoms
- Check engine light on, typically a short time after starting
- No obvious change in how the engine drives, since this sensor mainly monitors the catalytic converter
- Catalyst efficiency monitoring cannot run, so readiness monitors stay incomplete
- Vehicle cannot pass an emissions inspection
- Slightly higher fuel consumption on some vehicles that use this sensor for fine fuel trim
- Fault may come and go in wet weather
Likely causes
- Heater element open inside the downstream sensor
- Connector corroded or full of water, a very common problem in this location
- Harness chafed or crushed against the underbody, exhaust or a heat shield
- Blown fuse in the heater supply, sometimes shared with other sensors
- Corroded ground point for the downstream sensor heater
- Thermal shock after driving through standing water
- Failed heater driver in the control module
How to fix it
- Locate the downstream sensor and inspect its connector for water, corrosion and a damaged seal
- Measure heater element resistance at the sensor and compare with specification
- With the ignition on, check for supply voltage at the harness connector
- Voltage-drop test the heater ground, since corrosion under the vehicle is common
- Follow the harness along the underbody and look for crushed or chafed sections and rodent damage
- Repair the wiring, clean or replace corroded terminals and reseal the connector
- Replace the downstream sensor if its heater is open, then clear the code and let the readiness monitors run