Subaru Won’t Start? Common Causes and How to Diagnose
Most no-start Subarus trace back to a dead battery, a bad starter, a fuel system problem, or a security system lockout. You can narrow it down in under five minutes without special tools. Start with the checklist below, then follow the directed path for your specific symptom.
First, Check These Five Things
Make these quick observations before you grab any tools. They’ll point you to the right fix without guesswork.
1. Do the dashboard lights come on? If they’re dim or nothing lights up when you turn the key, the battery is almost certainly dead or the terminals are corroded.
2. Do you hear a single loud click or silence? A single click (or no sound at all) usually means the starter solenoid isn’t engaging. Rapid clicking points to a low battery.
3. Does the engine turn over but never fire? If it cranks normally but won’t start, the problem is fuel, spark, or the immobilizer – not the battery or starter.
4. Is the security light flashing? A blinking key or “Security” icon on the dash means the immobilizer isn’t recognizing your key. Try your spare.
5. Did the car run out of gas recently? If you ran the tank dry, air in the fuel lines can prevent starting. Cycle the key to ON three times (5 seconds each) to re-prime the system.
Result of these five checks: If a jump-start gets it going, you’ve found the battery issue. If the security light is flashing, jump to that section. If the engine cranks but won’t fire and the security light is off, move straight to fuel and spark diagnostics.
Battery and Electrical System
The battery is the most common Subaru no-start cause, especially in cold weather or after a few days of sitting.
Jump‑Start Test
Connect a known‑good battery or jump pack using the positive terminal and a clean ground point (not the negative battery terminal). If the car fires up, your battery is weak or dead. Drive at least 20 minutes to recharge it, then have the battery load‑tested at an auto‑parts store. Any voltage below 12.4V at rest means it needs charging or replacement.
Check the Terminals and Grounds
Corrosion on the battery terminals or a loose ground cable at the chassis can mimic a dead battery even when the battery is fine. Scrub terminals with a wire brush and tighten the clamps. Also check the main ground strap from the engine block to the frame – a broken ground on a Subaru can cause all kinds of electrical gremlins, from flickering lights to a no-crank condition. On 2005–2009 Legacy and Outback models, the ground strap at the passenger‑side strut tower is a known corrosion point.
Parasitic Drain (If It Happens Repeatedly)
If your battery keeps dying overnight or after a few days, your Subaru may have a parasitic drain. Common culprits on older models: the dome light staying on, a stuck glove‑box light, or an aftermarket accessory wired directly to the battery. You can test drain with a multimeter set to DC amps. Disconnect the negative battery cable, attach the meter in series between the negative post and the cable, and wait 15 minutes for the car’s modules to go to sleep. A reading above 50 mA means you have a drain worth chasing. On 2010–2014 Forester models, a faulty hatch‑switch circuit is a frequent offender.
Starter Motor Problems
If the battery is healthy (dash lights are bright) but you get a single click or silence, the starter is the likely suspect.
- Single click, no crank: The starter solenoid is engaging but the motor itself is stuck or burned out. Sometimes tapping the starter body with a long extension and hammer while someone turns the key can free a stuck starter – a temporary test, not a fix.
- Grinding noise: The starter gear isn’t meshing properly with the flywheel. This can damage the flywheel teeth. Stop trying immediately and have it towed. That’s your escalation signal for this section – don’t keep cranking.
- Silence after turning the key, with all dashboard lights on: Check the starter relay and fuse (fuse box under the hood, position varies by model). On many 2010–2018 Outbacks, the starter relay is marked “ST” – swap it with a known good relay of the same part number, such as the horn relay.
Testing the Starter Relay
Pull the starter relay, then use a multimeter to check for continuity across the coil terminals (typically pins 85 and 86). No continuity means the relay coil is open – replace it. If the relay clicks when you apply 12V across those pins but the car still doesn’t crank, the relay’s high‑current contacts may be burned. Swap in a known good relay to confirm.
Note on Subaru CVT models: Some newer Subarus have a neutral‑start switch that can fail. If the car won’t crank in Park but will crank in Neutral, that switch is the likely cause. On 2015–2020 Outbacks with CVT, the neutral‑start switch is part of the transmission range sensor and can be replaced without dropping the trans pan.
Fuel System Issues
If the engine cranks strongly but won’t fire, fuel delivery is a top suspect.
Listen for the Fuel Pump
Turn the key to the ON position (not START) and listen for a 2‑second whir from the rear of the car. No sound means the pump isn’t priming. Check these in order:
1. Fuel pump fuse (in the under‑dash or under‑hood fuse box).
2. Fuel pump relay – same swap test as the starter relay.
3. On older Subarus (pre‑2010), the fuel pump itself is common to fail, especially around 120,000–150,000 miles. On 2008–2014 Impreza and WRX models, the fuel pump controller (mounted near the pump) can also fail, cutting power even if the relay is fine.
Clogged Fuel Filter
Subaru recommends replacing the in‑line fuel filter every 30,000–60,000 miles. A restricted filter can let the engine idle but stall under load. If your car starts after sitting but dies on the road, change the filter first. On 2010‑and‑newer models, the filter is often integrated into the pump module, so you replace the whole assembly – check your service manual.
No Start After Running Out of Gas
If you ran the tank dry, air in the fuel lines can prevent the engine from firing. Cycle the key to ON (not START) three times, waiting 5 seconds each time, to re‑prime the system. Then try starting. If it still doesn’t catch, you may need to purge the air at the fuel rail – consult your owner’s manual. On 2005‑2012 Legacy/Outback models, there is a Schrader valve on the fuel rail: press the center pin with a rag to bleed air.
Security System Lockout
The Subaru immobilizer (labeled as “Security” or a key icon on the dash) can prevent the engine from starting even if everything else is fine.
- Flashing security light when the key is in the ON position: The immobilizer isn’t recognizing the key. Try the spare key. If the spare works, the original key’s transponder is dead. If neither works, the immobilizer module or antenna ring around the ignition may have failed.
- After a battery disconnect: Some Subaru models require a “relearn” procedure after the battery was disconnected for a while. Turn the key to ON for 10 seconds, then OFF. Repeat twice, then start. On some 2015+ models, you may need to lock and unlock the driver’s door manually to wake the system. On 2010–2014 Outback, holding the door unlock button for 5 seconds after reconnecting the battery can also work.
Match Your Symptom to the Fix
| Symptom | Likely Cause | Next Action |
|---|---|---|
| Dash lights dim or off | Dead battery or corroded terminals | Try jump start |
| Single click, no crank | Bad starter solenoid or motor | Tap starter body as a test |
| Rapid clicking | Low battery voltage | Jump start or charge battery |
| Engine cranks but no sound from fuel pump | Fuel pump fuse, relay, or pump | Check fuse and relay first |
| Flashing security light on dash | Immobilizer issue | Try spare key or relearn procedure |
| Grinding noise during crank | Starter gear or flywheel damage | Stop immediately – tow to a shop |
When the Engine Cranks But Won’t Start (Spark and Sensors)
If fuel delivery is confirmed (you hear the pump prime, the filter is clean), check for spark or engine sensor failure.
- No spark: Pull a spark plug, ground the threads against the engine, and have someone crank. No spark points to a bad ignition coil, crank position sensor, or camshaft position sensor. On Subaru EJ series engines, the crank sensor is a frequent failure – the engine will crank forever but never fire. On 2011–2018 FB series engines (Legacy, Outback, Forester), the camshaft position sensor on the driver’s side is a known weak point.
- Crank but no start with a check engine light: Scan the OBD2 codes. Common no‑start codes on Subarus: P0335 (crank sensor), P0340 (cam sensor), P0011/P0021 (VVT actuator stuck – can cause hard start or no start when advanced).
Common Sensor Failure Patterns by Subaru Engine Family
| Engine Family | Known Sensor Issues | Typical Mileage |
|---|---|---|
| EJ (1999–2014) | Crank position sensor, ignition coil | 100,000–150,000 |
| FB (2010–2020) | Cam position sensor (driver side), VVT solenoid | 80,000–120,000 |
| FA (2013–present) | Crank sensor, direct‑injection high‑pressure pump (no‑start on low fuel pressure) | 60,000–100,000 |
Verification after replacing a part: The engine should start within two cranks and idle smoothly. If it still doesn’t start, do not continue replacing parts randomly. This is your escalation threshold: stop DIY and take the car to a Subaru specialist or dealer. The issue is likely a timing chain misalignment, ECU failure, or internal engine problem that requires dealer‑level tools and experience.
Final success check: After the repair, confirm the car starts reliably across three separate cold‑start cycles (e.g., overnight). Normal startup means the engine catches immediately, the security light goes out, and there are no new dashboard warning lights.
Greedy Wheels is the founder and lead editor at Wheels Greed. With over 15 years of hands-on automotive experience — from rebuilding engines in a home garage to managing fleet maintenance for a regional logistics company — he brings real-world mechanical knowledge to every guide.
His work has been featured in automotive forums, owner communities, and dealership training materials. When he’s not researching the latest car owner questions, you’ll find him at a local track day, wrenching on his project car, or testing the newest OBD2 diagnostic tools.
At Wheels Greed, every article is reviewed against manufacturer service manuals, NHTSA bulletins, and verified owner reports. No AI-generated fluff. No guesswork. Just practical answers from someone who has turned the wrench.