P247B: Exhaust Gas Temperature Out of Range Bank 1 Sensor 4

What it means

The EGT sensor at bank 1 sensor 4 reports a value outside its plausible operating range over time - typically a degraded element giving an offset that the substitute logic flags as implausible.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

Bank 1 sensor 4 measures exhaust gas temperature at its position in the exhaust, and the control module checks whether that reading is plausible for current conditions. P247B sets when bank 1 sensor 4 stays outside its expected range, potentially because of sensor bias, damaged wiring, contamination, or an exhaust leak close to sensor 4.

Common causes

Most likely first.

1. Aged or biased exhaust-temperature sensor
2. Damaged wiring or poor connector contact
3. Sensor contaminated or damaged
4. Exhaust leak near the sensor

Symptoms

• Check-engine light on
• Possible reduced engine power
• Possible increased fuel consumption

How to diagnose it

1. Use freeze-frame data to identify the conditions when the fault occurred and compare bank 1 sensor 4's reading with other exhaust sensors.
2. With the exhaust cool, inspect the bank 1 sensor 4 connector and harness for heat damage, corrosion, loose pins, or contamination.
3. Check for an exhaust leak close to the bank 1 sensor 4 mounting location.
4. Review sensor 4 live data during warm-up and changing load for a response that is implausible relative to other sensors.
5. Check the bank 1 sensor 4 circuit and sensor against the manufacturer's specification before replacing parts.

Common fixes

• Repair damaged wiring or poor contact at the bank 1 sensor 4 connector.
• Repair an exhaust leak near bank 1 sensor 4.
• Replace a contaminated or damaged bank 1 sensor 4.
• Replace bank 1 sensor 4 if it remains out of specification after circuit checks.

Can I keep driving?

If the vehicle drives normally, keep trips short and arrange diagnosis. Avoid heavy loads if power is reduced, since an implausible bank 1 sensor 4 reading may interfere with emissions management and increase fuel use.