Why Toyota Prado 120 does not start: a complete analysis of the reasons and solutions

Toyota Prado 120 is a legendary SUV, but even it is not immune to starting problems. If your Prado 120 won't start, there can be dozens of reasons: from a dead battery to serious malfunctions in the fuel system or electronics. In this article we will analyze all possible scenarios - from the simplest to the complex ones that require the intervention of specialists.

It is important to understand that the symptoms of “won’t start” can manifest themselves in different ways: the engine may not respond to the key at all, turn the starter but not catch, or start and immediately stall. Each case requires its own approach. We have collected step by step instructions, which will help diagnose the problem even without deep knowledge in auto electrics.

We will pay special attention diesel and gasoline versions Prado 120 (1KZ-TE, 3RZ-FE, 1GR-FE), since they have specific “sores”. We will also look at cases when the car does not start. hot or when cold - this often indicates various malfunctions.

1. Primary diagnosis: what to check first

Rule out the obvious causes before you dig deep. Start with a visual inspection and simple checks:

• 🔋 Rechargeable battery: voltage must be no lower 12.4 V with the engine turned off. When trying to start, the voltage should not drop below 10 V.
• 🔌 Battery terminals: Oxidation or loose contact may simulate a dead battery. Try moving the terminals - if the engine comes to life, the problem is in them.
• 🔑 Immobilizer: The key icon on the instrument panel may light up or flash. If the immo does not recognize the key, the engine will not start.
• ⛽ Fuel: trivial, but check the gasoline/diesel level. On Prado 120 The level sensor sometimes lies.

If everything is fine with the battery and terminals, and the car shows no signs of life (the relay does not click, the starter does not turn), the problem may be main relay (under the steering column) or fuse box. On Prado 120 fuse often fails EFI (15A) - it is responsible for powering the engine ECU.

Important nuance: if the starter turns, but the engine does not catch, the problem is most likely in fuel system or ignition. If the starter does not turn, look for the problem in electrical (battery, starter, wiring).

2. Problems with the battery: how to check and “reanimate”

The battery is the most common reason why Toyota Prado 120 won't start. This is especially true for diesel versions (1KZ-TE) where high starting current is required. Here's how to check the battery correctly:

1. Engine off voltage: must be 12.6–12.8 V. If below 12.4 V - the battery is low.
2. Starting voltage: if it falls below 10 V, The battery is faulty or lacks capacity.
3. Electrolyte density: every jar should have 1.27–1.29 g/cm³ (checked with a hydrometer).

If the battery is discharged, try to “light it” from another car. On Prado 120 It is important to observe the polarity and connection sequence:

• ⚡ Connect first positive wire to the donor, then to your battery.
• ⚡ Then connect minus wire to the donor, and the other end to mass (for example, a bolt on the engine block).
• ⚡ Get a donor, let it work for 5-10 minutes, then try to get yours Prado.

If the battery is old (more than 5 years), it is better to replace it. For Prado 120 recommended parameters:

Engine type	Capacity (Ah)	Starting current (A)	Recommended Brand
Gasoline (3RZ-FE, 1GR-FE)	75–90	600–700	Varta, Bosch, Exide
Diesel (1KZ-TE)	90–100	750–850	Optima, Banner, Mutlu

⚠️ Attention: On diesel Prado 120 You cannot install a battery with a starting current below 700 A. A weak battery will not crank the starter in cold weather, and the engine will not start.

3. Starter: why doesn’t it turn or turns too slowly?

If you hear clicks when you turn the key, but the starter does not turn, the problem may be:

• 🔧 Solenoid relay (contacts often burn out).
• 🔧 Starter brushes (wear or hangup).
• 🔧 Bendix (the overrunning clutch does not engage the flywheel).
• 🔧 Wiring (break or poor contact on the power wire from the battery to the starter).

To test the starter, you can short circuit it directly. To do this:

1. Put the car in neutral and turn on the handbrake.
2. Remove the air filter to access the starter.
3. Use a screwdriver to close two large contacts on the solenoid relay (one from the battery, the second to the starter).
4. If the starter spins, the problem is in the solenoid relay or control circuit.

On Prado 120 The starter often “dies” due to moisture (for example, after washing the engine) or wear of the bushings. If the starter turns slowly, even with a new battery, check:

• 🔋 Battery charge (the generator may be faulty).
• 🔌 Engine weight (poor contact on the negative wire from the battery to the body/engine).
• 🛠️ Starter condition (wear of brushes or bearings).

How to remove the starter on a Prado 120 without a pit?

To remove the starter without a pit or lift:

1. Remove the engine protection (4 bolts).

2. Unscrew the starter mount (3 bolts: two on top, one on bottom).

3. Disconnect the wires (first negative, then positive).

4. Carefully pull the starter down, turning it for convenience.

⚠️ Attention: If the starter turns, but the engine does not catch, do not hold the key in the "start" position longer 5–7 seconds. This can lead to overheating of the starter or discharge of the battery.

4. Problems with the fuel system (gasoline vs diesel)

If the starter turns, but the engine does not start, the fuel system is to blame. Symptoms and solutions differ for gasoline and diesel engines Prado 120.

Gasoline engines (3RZ-FE, 1GR-FE)

Frequent problems:

• ⛽ Clogged injectors: The engine stalls or does not start. The solution is flushing or replacement.
• ⛽ Faulty fuel pump: When you turn on the ignition, you can’t hear the buzzing of the pump in the gas tank.
• ⛽ Clogged fuel filter: fuel pressure is below normal (2.5–3.5 bar).
• ⛽ Faulty fuel pressure regulator: Pressure is either too high or drops during startup.

To check the fuel system:

1. Listen to whether the fuel pump works when you turn on the ignition (in the cabin or under the rear seat).
2. Check the fuel pressure with a pressure gauge (connected to the fuel rail).
3. If there is no pressure, check the fuel pump fuse (EFI, 15A) and relay.

Diesel engines (1KZ-TE)

Diesel 1KZ-TE their "sores":

• ⛽ Airing the fuel system: After replacing the filter or repairing, you need to bleed the system.
• ⛽ Faulty injection pump: The engine does not start or runs rough.
• ⛽ Clogged injectors: black smoke, tripping, difficult cold starting.
• ⛽ Faulty fuel shut-off valve (on the injection pump).

For bleeding the fuel system on diesel engines Prado 120:

1. Unscrew the return fitting on the injection pump.
2. Pump the fuel with a hand pump (located on the fuel filter) until clean diesel appears without bubbles.
3. Tighten the fitting and try to start it.

Listen to the operation of the fuel pump (for gasoline)|Check the fuel pressure with a pressure gauge|Inspect the fuel filter for clogging|Check the fuse and relay of the fuel pump|For diesel: bleed the system from air-->

On diesel Prado 120 with a mileage of more than 200 thousand km, the plunger pair in the injection pump often fails. Symptoms: the engine starts only “hot” or after prolonged cranking with the starter.

5. Problems with ignition and electronics

If fuel is supplied but the engine does not start, the ignition system or electronics are to blame. On Prado 120 common problems:

• 🔥 Faulty spark plugs (gasoline) or glow plugs (diesel).
• 🔥 Breakdown of high-voltage wires or ignition coils.
• 🔥 Faulty crankshaft sensor (DPKV) - the engine will not start at all.
• 🔥 Problems with the ECU (for example, after washing the engine or a short circuit).

How to check:

• 🔧 Spark plugs: Unscrew and inspect. Carbon deposits, oil or cracks are a sign of a malfunction.
• 🔧 Ignition coils: Swap places with a known working one. If the cylinder starts working, the coil is faulty.
• 🔧 Crankshaft sensor: Check the resistance with a multimeter (should be 500–700 Ohm).

On diesel Prado 120 (1KZ-TE) often fail glow plugs. If the engine does not start when cold, but runs normally when hot, check:

1. Candle resistance (should be 0.5–6 Ohm).
2. The voltage on the spark plugs when the ignition is on (10–12 V).
3. The performance of the glow plug relay (located in the fuse box).

6. The engine starts and immediately stalls: reasons

If Toyota Prado 120 starts, but immediately stalls, this indicates:

• 🛢️ Insufficient fuel pressure (clogged filter, weak pump).
• 🔍 Air leak in the intake manifold or vacuum hoses.
• 🔧 Faulty mass air flow sensor (MAF).
• 🔧 Throttle problems (dirty or faulty position sensor).

For diagnostics:

1. Check error codes scanner (for example, P0171 - lean mixture P0300 — misfires).
2. Inspect vacuum hoses for cracks or loose connections.
3. Try starting the car with ajar throttle (press the gas lightly). If the engine continues to run, the problem is in the idle system.

On diesel Prado 120 common reason - faulty EGR valve or clogged intercooler. This leads to unstable operation and engine stalling.

7. Prado 120 does not start when hot: specific reasons

If the car won't start only for hot, to blame:

• 🔥 Ignition coils (insulation breakdown when heated).
• 🔥 Coolant temperature sensor (DTOZH) — supplies incorrect data to the ECU.
• 🛢️ Fuel pump (on gasoline versions it may overheat and turn off).
• 🔧 Starter (worn bushings or brushes do not provide normal contact when heated).

For diagnostics:

1. After stopping the engine, check ignition coil temperature - if they are too hot, there is most likely a breakdown.
2. Listen to see if it works fuel pump after warming up (sometimes it turns off due to thermal protection).
3. Check fuel pressure on a hot engine - it may drop due to a faulty regulator.

On diesel Prado 120 the problem is often injection pump — when heated, the plunger pair may jam or not create the required pressure.

8. When diagnostics are indispensable: complex cases

If you have checked all of the above, but Prado 120 still won't start, the problem could be:

• 🔧 Engine ECU (for example, after a short circuit or washing).
• 🔧 Immobilizer (does not recognize the key or a failure in the control unit).
• 🔧 timing belt (broken belt or skipped marks).
• 🔧 Camshaft position sensor (CPR).

In these cases, without diagnostic scanner (for example, Launch X431 or Autel) can't be avoided. Please note the following errors:

Error code	Meaning	Possible reason
P0335	Crankshaft position sensor malfunction	Problems with DPKV, broken wiring or damage to the flywheel ring gear
P0340	Camshaft position sensor malfunction	Problems with DPRV or timing belt
P0606	ECU error	Malfunction of the control unit, power problems or firmware glitch
P1600	No communication with immobilizer	Problems with the chip in the key, immo antenna or control unit

If the scanner shows errors timing belt (P0340, P0341), do not try to start the car - this may cause the pistons to collide with the valves and major renovation!

⚠️ Attention: If after washing the engine Prado 120 stopped starting, most likely water got into the connectors of the sensors or the ECU. It is necessary to dry the electronics (you can use a hairdryer) and check the circuits for short circuits.

FAQ: Frequently asked questions about launching Prado 120

Why doesn't Prado 120 start after refueling?

Possibly low-quality fuel got into the tank. For gasoline engines (3RZ-FE, 1GR-FE) it could be low octane gasoline or water in the fuel. For diesel (1KZ-TE) - bad diesel fuel or clogged fuel filter.

Solution:

1. Drain the fuel from the tank.
2. Replace the fuel filter.
3. Add fuel system cleaner (such as Liqui Moly or Wynn's).

Prado 120 does not start after replacing the battery - what to do?

After replacing the battery, throttle adaptation may be disrupted or the immobilizer may not recognize the key. Try:

1. Reset the battery terminals for 10 minutes, then connect again.
2. Carry out throttle valve adaptation (on petrol versions):

1. Ignition ON for 3 seconds.
2. Turn off the ignition for 5 seconds.
3. Start the engine and let it idle for 5 minutes.

3. If the problem is in the immobilizer, rewrite the key (you need a diagnostic scanner).

The starter turns, but the Prado 120 does not engage - what's the matter?

Reasons:

• 🔥 No spark (check spark plugs, coils, ignition module).
• ⛽ No fuel (check the fuel pump, filter, rail pressure).
• 🔧 Sensors (DPKV, DPRV, DMRV) are faulty.
• 🔧 The timing marks are knocked off.

Start by checking sparks and fuel pressure. If everything is in order, diagnose the sensors and ECU.

Prado 120 diesel does not start when cold - what to do?

Typical diesel problems 1KZ-TE:

• ❄️ Glow plugs do not work (check resistance).
• ❄️ Airing the fuel system (pump).
• ❄️ Thickened diesel fuel (use anti-gel in cold weather).
• ❄️ The injection pump or injectors are faulty.

Try:

1. Warm up the glow plugs 2-3 times for 10 seconds.
2. Add antigel to the fuel (for example, Liqui Moly Diesel Fliess-Fit).
3. Bleed the fuel system manually.

Is it possible to start the Prado 120 from a pushrod?

Start up Prado 120 from the pusher not recommended, especially if the problem is in the timing belt or transmission. However, in emergency cases:

• 🚗 Put the car in neutral.
• 🚗 Speed up to 10–15 km/h.
• 🚗 Turn it on second gear and release the clutch.
• 🚗 As soon as the engine catches, immediately press the clutch.

Dangers:

• ⚠️ Risk of damage to the catalyst (if the engine does not start and fuel continues to flow).
• ⚠️ Jerks and loss of control are possible.