Diagnostics Engine never shuts off
Symptom
Why is my hybrid's engine running all the time?
If your hybrid's gas engine never seems to shut off, even at stoplights, even on flat ground, the battery is the most likely reason.
What it means
A healthy hybrid lets the gas engine shut off in many conditions: at stoplights, when coasting, when cruising on a flat highway in the right speed range. If the engine refuses to shut off in those conditions, the system has decided the battery can't be trusted to carry the load.
Vehicles where we see this most
- Toyota Prius (all generations)
- Toyota Camry Hybrid
- Honda Civic Hybrid
- Ford Escape Hybrid
Most-likely causes
- Hybrid battery state-of-charge can't hold steady. The pack is weak.
- Cold weather (the engine warms cabin and catalyst, won't shut off until both are warm).
- Climate control on max heat (same reason).
- Failing 12V battery causing odd hybrid behavior.
Is it really the battery?
Often, especially if it happens in mild weather with climate control off. If it only happens when it's freezing or you've got the heat blasting, that's normal hybrid behavior, not a fault.
What to do next
- Test in mild weather with climate off. If the engine still won't shut off at a stoplight, you've got a real problem.
- Watch the energy-flow display: a healthy battery shows the state-of-charge bar moving up and down smoothly. A failing one swings full-to-empty fast.
- Get codes scanned. P0A7F or P0A80 confirms it's the pack.
- If everything points at the pack, take the quiz or call us for an honest quote.
Take the quiz
Not sure if this is what's wrong with your car?
Five questions, built by our techs. We'll tell you honestly whether it sounds like the pack, or something cheaper.