The car does not turn off with the key: reasons and what the driver should do

Have you turned the key to the "off" position, but the engine continues to run, as if not noticing your actions? The situation when car won't turn off with key, is not only annoying, but also signals serious problems in the car’s electrical system. At best, this is an annoying little thing that will force you to manually turn off the engine by removing the battery terminal. At worst, it's a risk. engine overheating, battery discharge or even fire due to a short circuit.

In this article we will look at all possible reasonswhy the engine ignores the shutdown command - from banal wear of the ignition switch contacts to failures in the control unit. You will learn how to diagnose the problem yourself (even without an OBD-II scanner), which components to check first, and when you should immediately go to a service station. And for car owners with alarm system StarLine, Pandora or autostart - a separate section with typical “jambs” of these systems.

Important: if your machine is equipped gas cylinder equipment (GBO), the troubleshooting algorithm will be different - we will also talk about this below. Don't miss it FAQ at the end of the article, where common questions are addressed, for example, why the engine does not turn off at idle or after washing.

1. Why the car won’t turn off with the key: top 7 reasons

Let's start with the most obvious: when you turn the key to LOCK (or press the button START/STOP on keyless systems), the starter power circuit is opened, and the ECU (electronic control unit) receives a signal to stop the engine. If this does not happen, one of the 7 nodes is to blame:

• 🔑 Ignition switch — wear of the contact group or mechanical failure of the cylinder. More common on cars older than 10 years (VAZ 2110-2115, Renault Logan, Chevrolet Niva).
• 🔋 Starter — “sticking” of the solenoid relay or burnt contacts (“nickel”). Typical for cars with high mileage or after unsuccessful attempts to start by “lighting up”.
• 📶 Immobilizer/alarm — failure of the data exchange protocol between the key fob and the ECU. It often appears after replacing the battery or flashing the firmware.
• 🖥️ Electronic control unit (ECU) — errors in the firmware or physical damage to the board (for example, after a short circuit).
• ⚡ Fuel pump/ignition relay — “stuck” in a closed state due to oxidation of contacts.
• 🔧 Additional equipment — incorrectly installed LPG, autostart or security system that blocks the signal to turn off.
• 🚗 Mechanical problems — a jammed throttle cable (on carburetor cars) or a faulty crankshaft position sensor (CPS).

According to STO statistics, in 60% of cases the ignition switch or starter is at fault, 25% - problems with electronics (ECU, alarm), and only in 15% - mechanical failures. But to accurately determine the cause, you need to conduct a diagnosis.

2. Diagnostics: where to start if the engine does not turn off

Before disassembling half of the machine, perform 5 simple stepsto help narrow your search:

1. Try it turn off the ignition again. Sometimes the contacts get stuck due to moisture or oxidation, and a second try is enough to break the circuit.

2. Check Is the Check Engine light on? on the dashboard. If yes, most likely the problem is in the ECU or sensors (you need a scanner to read errors).

3. Disable all additional equipment: radio, recorder, navigator. Sometimes they create stray currents that interfere with the operation of the ignition switch.

4. Try turning off the engine alternative way:

   • 🔧 On a manual transmission: depress the clutch and engage 3rd gear (the engine will stall from the load).
   • 🔋 On automatic: remove the battery terminal (negative!).
   • 🚗 On carburetor cars: turn off the air supply with your hand (be careful - you can get burned!).

Inspect wiring under the hood for melted wires or traces of a short circuit (especially around the starter and ECU).

If the engine still does not turn off, proceed to a detailed check of each component. Let's start with the most common - ignition switch.

3. Ignition switch: how to check and repair

The ignition switch is mechanical device with contact group, which wears out over time. Typical signs of its malfunction:

• 🔑 The key turns with difficulty or “skips” positions.
• ⚡ The dashboard does not respond to turning the key (the lights do not light up).
• 🔥 A burning smell appears from under the steering wheel (contacts are burning).
• 🚗 The engine starts/stops every other time.

To check the lock, follow these steps:

1. Remove plastic steering column cover (usually it is secured with latches or bolts). Be careful not to damage the wiring of the steering column switches!

2. Disconnect ignition switch connector and inspect the contacts for oxidation or burning. If they are black or green, sand them with sandpaper or replace the contact group.

3. Check integrity of wires, going from the lock to the starter and the ECU. They often rub against the steering shaft.

4. If the castle mechanically sound, but the problem remains - check larva. Insert the key and swing it to the sides. Play of more than 1–2 mm indicates the need for replacement.

On some vehicles (for example, Ford Focus 2, Toyota Corolla) the ignition switch is combined with immobilizer. In this case, simply replacing the contact group will not help - you will need flashing keys at the service station.

How to temporarily turn off the engine without repairing the lock?

If the ignition switch breaks down on the road, you can turn off the power to the starter manually:

1. Locate the starter relay in the fuse box (usually labeled "Starter" or "Ignition").

2. Pull out the relay - the engine will stall the next time you press the brake (automatic) or clutch (manual).

3. To start the car again, insert the relay back and use a screwdriver to turn the lock cylinder (if it does not lock the steering wheel).

4. Starter and solenoid relay: symptoms and repairs

If when you turn the key to position LOCK audible clicking sound, but the engine does not turn off, the problem may lie in starter solenoid relay. This unit is responsible for opening the power circuit after starting the engine. When the relay gets stuck, the starter continues to turn the flywheel even after the key is released.

How to diagnose a malfunction:

1. Listen: if after turning off the ignition you hear crunching or grinding on the starter side - the relay does not disconnect it from the flywheel.

2. Check control wire voltage solenoid relay (usually a thin wire at the starter connector). There should be no voltage when the ignition is turned off!

3. Remove the starter and disassemble it. Usually the problem is:

   • 🔥 Burnt contacts (“nickels”) - they can be cleaned or replaced.
   • 🧲 Weakened spring solenoid relay - it does not return the core to its original position.
   • 🔋 Short circuit in winding relay (checked with a multimeter).

On vehicles with Start/Stop system (for example, Volkswagen, BMW, Mercedes) the starter is controlled by the ECU, and its “sticking” may be due to firmware failure. In this case, only flashing at a dealer service station will help.

5. Problems with alarm and immobilizer

Modern security systems (StarLine, Pandora, Scher-Khan) are often the reason why car won't turn off with key. This happens due to:

• 📱 Communication protocol failure between the key fob and the alarm unit (for example, after replacing the battery in the key fob).
• 🔌 Incorrect installation autostart when the alarm unit conflicts with the ECU.
• 🔐 Immobilizer activation (for example, if the key is not recognized after washing or impact).
• 📡 Interference from other devices (for example, if there is a powerful radio transmitter nearby).

How to fix the problem:

1. Try it turn off the engine using the key fob (if there is such a function). On some alarms (Pandora DXL) to do this you need to hold the button Close 3 seconds.

2. Reset the alarm settings to factory settings (instructions are in the manual for your model). This is usually done by a sequence of clicks on Valet and Override.

3. Check immobilizer fuse (usually it is located in the fuse box under the hood and is labeled as IMMO or Transponder).

4. If all else fails - turn off the alarm completely, removing the main fuse (but keep in mind that the car will remain unprotected!).

On vehicles with keyless entry (Keyless Go) the problem may lie in immobilizer antenna, which is located around the ignition switch. If it is damaged, the ECU does not “see” the key and blocks the engine from turning off.

6. Electronic control unit (ECU) and sensors

The ECU is the brain of the car, and if it malfunctions, the engine may ignore commands to shut down. Typical reasons:

• 🖥️ Errors in the firmware (for example, after unsuccessful chip tuning).
• ⚡ Short circuit on the ECU board (often due to moisture).
• 📊 Sensor malfunction:
  • Crankshaft position sensor (CPS) - if it is lying, the ECU does not “understand” that the engine is running.
  • Idle speed sensor (IAS) - can force the engine to operate at higher speeds, preventing it from turning off.
  • Mass air flow sensor (MAF) - its malfunction leads to malfunctions of the ECU.

ECU diagnostics require OBD-II scanner (for example, ELM327 or Launch X431). Connect it to the connector (usually located under the steering wheel) and check the error codes. The most critical for our problem:

Error code	Meaning	What to do
P0335	Crankshaft position sensor circuit malfunction	Check the wiring and replace the DPKV
P0507	High idle speed	Clean the throttle body, check the DHW
P1600	Immobilizer communication error	Check immobilizer antenna and keys
U0100	Loss of communication with the ECU	Check the fuses and power supply circuits of the unit
B1200	Alarm fault	Reset or disable the security system

If the scanner shows errors related to CAN bus (for example, U0001), the problem may be a broken wire or short circuit. In this case, it is better to contact a service station - CAN bus repair requires special equipment.

7. Additional equipment: HBO, autostart, radio

If your machine is equipped gas cylinder equipment (GBO), autostart system or powerful audio system, they may interfere with the normal shutdown of the engine. Let's consider typical scenarios:

• 🚗 HBO 4th generation: if the gas control unit (Stag, Lovato, BRC) does not go into mode Benzina (gasoline) when the ignition is turned off, the engine continues to run on gas. Check:
  • Settings Auto switching in the HBO menu.
  • Integrity of the wire from the HBO button to the ECU.
  • Gearbox temperature sensor (if it lies, the unit does not switch to gasoline).
• 🔑 Autostart: If the system is not installed correctly, it may block the shutdown signal from the ignition switch. Try disabling autostart in the key fob settings.
• 🎵 Radio/amplifier: Powerful audio systems (especially those with a subwoofer) can create power surges, interfering with the operation of the ECU. Turn off the radio and check if the engine turns off.

On vehicles with diesel engine the problem may be related to electronic fuel shut-off valve (for example, on Volkswagen TDI, BMW d). If it sticks in the open position, the engine will not turn off. Test it by applying voltage directly from the battery - if the valve does not close, replacement is required.

FAQ: Frequently asked questions about the problem

Why doesn't the car turn off with the key, but turns off with the alarm key fob?

This is a typical situation when alarm takes over control ignition. Most likely, when installing the security system, the technician connected it parallel to the ignition switch circuit, and now the alarm unit duplicates (or blocks) commands. Solution:

1. Check the alarm settings - the turbo timer mode may be turned on (the engine runs for several minutes after being turned off).
2. Reset the alarm to factory settings (instructions in the manual).
3. If the problem persists, contact your installer for flashing the alarm unit.

The engine does not turn off at idle, but does turn off in gear. What's the matter?

This problem is typical for cars with manual transmission and is related to:

• 🔧 Malfunction of the idle speed sensor (IAC) - it maintains speed even when the key is in position LOCK.
• ⚡ Short circuit in the ignition coil power circuit — the engine continues to receive a spark.
• 🖥️ Failure in the ECUwhen the block “does not see” the stop command (often after flashing).

Solution: check the IDC (clean or replace), inspect the ignition coil wiring and reset the ECU errors.

After washing the car the key will not turn off. What to do?

Water could get into:

• 🔑 Ignition switch - dry it with a hairdryer or WD-40.
• 🖥️ ECU or alarm unit - if they are located under the driver’s feet (for example, on VAZ 2114, Renault Megane), removal and drying are required!
• ⚡ Sensor connectors (DPKV, DMRV) - oxidation of contacts leads to failures.

⚠️ Attention: If water gets into the ECU, do not try to dry it with a household hairdryer - this may damage the microcircuits. Use special cold air blowing or silica gel.

The car doesn't turn off when it's cold, but it turns off normally when it's hot. Why?

This problem is often associated with:

• 🔥 Burnt contacts of the starter or ignition switch - when cold, the metal contracts and contact disappears.
• 🖥️ Malfunction of the coolant temperature sensor (DTOZH) — The ECU “thinks” that the engine is cold and maintains speed.
• ⚡ Weak battery - at low voltage, the ECU may not process signals correctly.

Solution: check the battery voltage (must be at least 12.4 V), inspect the starter contacts and replace the DTOZH if it is lying.

Is it possible to drive if the car does not turn off with the key?

⚠️ Attention: drive with this problem highly not recommended for several reasons:

• 🔥 Risk engine overheating, if it does not turn off due to a stuck starter.
• 🔋 Low battery — if the engine is running without load, the generator does not have time to charge the battery.
• 💥 Opportunity fire due to a short circuit in the ignition circuit.

If the problem appears while on the road, turn off the engine manually (for example, by engaging a manual gear) and urgently go for diagnostics. If the malfunction is related to the computer or alarm system, it is better to call a tow truck - independent repairs may worsen the situation.