What does it mean?
P1118 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: O2 Sensor Heater Circ. (Bank 1-Sensor2) Open .
Symptoms
- Check engine light on with the downstream sensor slow to become active
- Catalyst and oxygen sensor readiness monitors not completing, blocking an emissions test
- Sensor signal flat until the exhaust gas heats it, taking much longer than normal
- Slightly higher fuel consumption on vehicles that trim from the rear sensor
- Cold, damp weather makes the delay noticeably worse
- No obvious drivability complaint in most cases
Likely causes
- Open heater element inside the sensor, the most common cause on a high-mileage vehicle
- Blown fuse feeding the oxygen sensor heaters
- Broken heater supply wire or a failed relay in the supply path
- Open heater control wire between the sensor and the module
- Corroded or unlatched connector under the vehicle where water collects
- Harness burnt or broken where it lies against the exhaust
- Failed heater driver inside the module, checked once the wiring and sensor are proven
How to fix it
- Check the fuse that feeds the oxygen sensor heaters before anything else, since one blown fuse can set several codes
- With the ignition on, measure for battery voltage at the heater supply pin of the sensor connector
- Measure the heater element resistance across the sensor's heater terminals; an open reading condemns the sensor
- Check the heater control wire for continuity back to the module and confirm the module pulls it to ground when commanded
- Inspect the connector for water, corrosion and a broken latch, and reseal it after cleaning
- Repair any burnt or broken harness section along the exhaust and re-route it clear of heat
- Replace the sensor if the element is open, then confirm the sensor becomes active quickly on the next cold start