Exhaust Gas Temperature Sensor Circuit Low (Bank 1 Sensor 1)

What it means

The exhaust gas temperature (EGT) sensor signal voltage is below the normal range. The exhaust gas temperature (EGT) sensor measures exhaust temperature to protect the turbo and catalyst, and to control DPF regeneration on diesels. A low signal is usually caused by a short to ground, a missing reference voltage or a failed sensor.

Symptoms

• Check engine light on
• DPF regeneration problems (diesel)
• Reduced power

Probable causes

Most likely first

1. 1Signal wire shorted to ground (chafed against the body or engine)
2. 2Failed sensor shorted internally (it reads extremely hot)
3. 3Water or coolant inside the connector

How to diagnose it

Work through these in order before buying parts

1. 1Record the code and its freeze frame data (speed, load, temperature when it set), then clear it and see if it comes back.
2. 2Inspect the exhaust gas temperature (EGT) sensor connector and wiring (screwed into the exhaust before or after the turbo, catalyst or DPF). Look for corrosion, bent or pushed-back pins, oil contamination and chafed insulation.
3. 3Watch the exhaust gas temperature (EGT) sensor reading on live data. Cold engine: EGT should match outside temperature. It should rise quickly once the engine runs.
4. 4Unplug the sensor and measure its resistance; it should drop smoothly as it warms up (compare with the chart in a service manual). With the key on, the ECU side of the connector should show about 5 volts on the signal wire and a good ground on the other.
5. 5If the wiring checks out, test the sensor itself against the specification in a service manual.
6. 6Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.

Common fixes

• Repair the damaged wiring or connector
• Replace the exhaust gas temperature (EGT) sensor
• Clear the code and test drive to confirm the repair