Starter turns, car will not start: P0513, key not recognised

The starter spins briskly, there is fuel, there should be a spark — and the engine will not catch. If a key or car-with-padlock symbol flashed on the dashboard, the engine is not to blame: the unit did not recognise the key and blocked the start.

You can tell this state from a real fault in ten seconds without connecting anything: switch on the ignition and look at the immobiliser symbol. On a healthy car it lights for a couple of seconds and goes out. Flashing or staying on means the key was not recognised, and the engine will not start however long you crank.

How it works

Inside the key head sits a transponder — a small chip with no battery. An antenna is wound around the ignition lock. When you turn the key the antenna powers the chip with its field, the chip replies with its number, and the unit checks it against the list of «its own».

No match, and the unit blocks the fuel or the spark. The starter carries on as if nothing happened: it has nothing to do with the immobiliser.

Hence the picture that confuses people: «it cranks briskly, the battery is good, and it will not start».

P0513 and what it means

The code means exactly one thing: the engine unit received no confirmation that the key belongs. It does not say whose key it is or what exactly broke — only that there was no answer.

The causes in order of frequency, not of price:

1. A flat battery in the key — if yours has buttons and a transponder in one case. Plain transponders have no battery; combined ones do.
2. A second key on the ring. Two transponders near the antenna jam each other. Take everything else off the ring and try with one key.
3. A broken or unsoldered antenna around the lock. A common casualty after the steering column shroud has been off.
4. A sagging power supply. The immobiliser is part of the body electronics, and at low voltage it does not manage to agree with the engine unit in time. Check with control module voltage; the procedure is in charging and vehicle voltage and in how to check the battery and alternator.
5. Lost communication between modules. If U codes sit next to P0513, read those first: lost communication. The immobiliser is honestly silent because it has nobody to talk to.

What to try right now

1. The spare key. The quickest test of all: if it starts, the first key is at fault, and that is a cheap repair.
2. Take the other transponders and fobs off the ring.
3. Hold the key right against the lock or the marked spot on the column — many cars have an emergency reading zone.
4. Check the terminals. A sagging supply is the cause found last although it is checked first.
5. Recall yesterday: an alarm fitted, a lock replaced, the battery removed, the car washed. Splicing into the wiring is a common cause.

What not to do

Clear the code and try again. Clearing does not program a key: the code comes back at the next attempt, and the self-tests reset with it — so the emissions test has to wait. What that button actually does is in clearing a code.

Search the internet for «immobiliser bypass». This is an anti-theft system; defeating it leaves the car open to anyone who wants it.

⚠️ And honestly about the limits: a key cannot be programmed with an ordinary adapter. That is a factory procedure on a closed protocol and needs dealer equipment — for the same reason ABS and airbag faults are not visible over OBD-II. The app does something different but no less useful here: it shows that the trouble is the immobiliser rather than the pump, the plugs or the crankshaft sensor — so you arrive at the workshop with an answer rather than a question.

If the immobiliser symbol is not lit and the car still will not start, that is a different question — start from the symptom the starter turns but the engine will not fire and check the fuel pump relay.