Exhaust Gas Recirculation Sensor "A" Circuit Low

What it means

The EGR position sensor signal voltage is below the normal range. The EGR position sensor reports how far open the exhaust gas recirculation (EGR) valve is. A low signal is usually caused by a short to ground, a missing reference voltage or a failed sensor.

Symptoms

• Check engine light on
• Rough idle
• Hesitation
• Pinging under load

Probable causes

Most likely first

1. 1Open or shorted 5-volt reference wire from the ECU
2. 2Signal wire shorted to ground
3. 3Unplugged, corroded or loose connector
4. 4Failed sensor
5. 5Another sensor on the same 5V reference circuit shorting it down

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 EGR position sensor connector and wiring (on top of the EGR valve). Look for corrosion, bent or pushed-back pins, oil contamination and chafed insulation.
3. 3Watch the EGR position sensor reading on live data. Command the EGR valve open with a bidirectional scan tool and watch the position reading follow.
4. 4With the key on and the sensor unplugged, check for about 5 volts on the reference wire and a good ground (under 0.1 V drop) on the ground wire. Back-probe the signal wire with the sensor connected and watch the voltage change smoothly.
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 EGR position sensor
• Clear the code and test drive to confirm the repair