What it means
EGR temperature sensor A signal jumps or drops out intermittently. EGR mixes inert exhaust into intake to lower combustion peak temperature — too little raises NOx, too much causes misfires and rough running.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
EGR temperature sensor A reports exhaust gas temperature in the EGR path to the control module. P040E sets when that signal intermittently jumps or drops out instead of changing steadily with temperature.
Common causes
Most likely first.
- Intermittent connector
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
Symptoms
- Check engine light on
- Pinging or knocking under load
- Power loss and hesitation
- Possible rough idle
- Failed emissions inspection (NOx)
How to diagnose it
- Record freeze-frame data and review sensor A's live readings or scan-tool graph for sudden dropouts or jumps.
- Inspect sensor A's connector for loose or corroded terminals and its harness for chafing or contact with vibrating or hot parts.
- With the engine safely running and the scan tool connected, gently move the accessible harness and connector to see whether the reading cuts out.
- Check sensor A's signal, reference, and ground circuits for intermittent opens or shorts using the wiring diagram.
- If the wiring checks out, monitor sensor A as the EGR path warms and test it against the manufacturer's specification.
Common fixes
- Secure a loose connector or repair poor terminal contact at sensor A.
- Reroute or protect a harness that is chafing or vibrating against another component.
- Repair an intermittent open or short in sensor A's wiring.
- Replace EGR temperature sensor A if its output drops out despite a sound circuit.
Can I keep driving?
A short drive may be possible if the fault is not causing drivability symptoms, but avoid heavy loads if knocking or hesitation appears. Intermittent EGR feedback can worsen without warning, disrupt EGR control, and increase emissions.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.