Hard Starting / Long Crank — 2016 Toyota Mirai Cost & Fixes

Is your 2016 Toyota Mirai taking an unusually long time to become 'READY' after you press the power button? This symptom, often described as 'hard starting' or 'long crank' in traditional internal combustion engine vehicles, translates to a delayed system initialization in your Fuel Cell Electric Vehicle (FCEV). Instead of an engine physically cranking, your Mirai's sophisticated fuel cell system, high-voltage battery, and associated electronics are performing a series of checks and preparations before allowing the vehicle to drive. When this process takes longer than usual, it signals an underlying issue that requires attention. Understanding the potential causes, how to verify them, and the associated repair costs is crucial for any 2016 Toyota Mirai owner facing this concern.

At a glance: difficulty, repair cost, and diagnostic workflow

• Difficulty Rating: 6/10 — Easy to moderate
• Common Symptoms: Warning Lights on the Dashboard: The most obvious indicators are illuminated check engine light, fuel cell system warnin; Reduced Power or Performance: After the vehicle eventually goes 'READY', you might notice a decrease in acceleration or ; Unusual Noises: Listen for abnormal whirring, clicking, or grinding sounds during the extended startup sequence, which c; Difficulty Charging the 12V Battery: If the 12V battery is the culprit, you might find it frequently drained or unable t
• Estimated Repair Cost: $80–$900 (parts + typical shop labor)
• OEM Tooling Required: Standard OBD-II scanner and hand tools

Diagnostic workflow:

1. Confirm the symptom on your vehicle.
2. Scan for stored or pending codes with an OBD-II tool.
3. Inspect the most common causes in this guide (visual checks first).
4. Run verification tests before replacing parts.
5. Repair, clear codes, and verify on a test drive.

What is 'Hard Starting' or 'Long Crank' in a 2016 Toyota Mirai?

For a 2016 Toyota Mirai, 'hard starting' or 'long crank' doesn't refer to an engine's mechanical rotation. Instead, it describes a scenario where the vehicle takes an extended period to transition from the 'ON' state (after pressing the power button) to the 'READY' state, indicated by the 'READY' light illuminating on the dashboard. During this delay, you might hear various pumps or fans operating, but the vehicle doesn't fully activate for driving. This can manifest intermittently, sometimes occurring only when the vehicle is cold, or conversely, after it has been driven and is warm. The Mirai's complex system relies on precise coordination between its hydrogen fuel supply, fuel cell stack, power control unit, and 12V auxiliary battery to achieve operational readiness. Any disruption in this sequence can lead to these frustrating delays.

Common Causes of Hard Starting / Long Crank in a 2016 Toyota Mirai

The 2016 Toyota Mirai, being an FCEV, has a unique set of components that can contribute to a delayed 'READY' state. Unlike gasoline cars, you won't be looking at spark plugs or fuel injectors, but rather components related to hydrogen, fuel cell operation, and electrical systems.

Here are some of the most common culprits:

• Weak or Failing 12V Auxiliary Battery: This is arguably the most frequent cause of starting issues in any hybrid, EV, or FCEV. The 12V battery powers the vehicle's computers, relays, and initial system checks. If it's weak, it may not provide enough power for the main fuel cell system to properly initialize, leading to extended delays or even a no-start condition. Even if it can barely power the dashboard lights, it might not have the necessary cold cranking amps (or rather, cold system initialization amps) to bring the entire FCEV system online.
• Fuel Cell System Component Issues: The Mirai's core is its fuel cell stack. Problems with components that support its operation can cause delays:
  • Hydrogen Pressure Sensors: Faulty sensors might incorrectly report hydrogen levels or pressure, preventing the system from activating.
  • Hydrogen Regulators or Injectors: Issues with the precise delivery of hydrogen to the fuel cell stack.
  • Air Compressor: The fuel cell requires a steady supply of oxygen, provided by an air compressor. A malfunctioning compressor can delay or prevent the fuel cell from generating power.
  • Humidifier System: The fuel cell stack needs specific humidity levels to operate efficiently. Problems here can impact performance.
• Power Control Unit (PCU) or Inverter Malfunction: The PCU manages the flow of power between the fuel cell, high-voltage battery, and electric motor. A fault in this critical component can disrupt the entire startup sequence.
• High-Voltage (HV) Battery Issues: While the fuel cell generates primary power, the HV battery assists during acceleration and stores regenerated energy. If the HV battery's state of charge is critically low or if there's an internal fault, the system may delay going 'READY' as it tries to self-diagnose or charge.
• System Relays or Fuses: A blown fuse or a failing relay in a critical circuit (e.g., for the fuel cell system, hydrogen pump, or PCU) can prevent specific components from energizing, leading to startup delays.
• Software Glitches or Corrupt ECU Data: In rare cases, a software bug or corrupted data in the vehicle's various Electronic Control Units (ECUs) can cause intermittent startup issues. A software update or ECU reset might be necessary.

Related guides on this vehicle

• Safely Jump-Start a Dead Car Battery 2016 Toyota Mirai
• Brakes Making Grinding Noise 2016 Toyota Mirai
• Brake Pedal Hard to Push While Driving 2018 Toyota Mirai

Symptoms Accompanying Hard Starting

When your Mirai is experiencing hard starting, it's rarely an isolated issue. Other symptoms can provide valuable clues about the underlying problem:

• Warning Lights on the Dashboard: The most obvious indicators are illuminated check engine light, fuel cell system warning light, or a 12V battery warning light.
• Reduced Power or Performance: After the vehicle eventually goes 'READY', you might notice a decrease in acceleration or overall power.
• Unusual Noises: Listen for abnormal whirring, clicking, or grinding sounds during the extended startup sequence, which could point to a failing pump or compressor.
• Difficulty Charging the 12V Battery: If the 12V battery is the culprit, you might find it frequently drained or unable to hold a charge.
• Intermittent Operation: The problem might only occur under specific conditions, such as after sitting overnight in cold weather, or after a short drive.
• Inconsistent Readiness: Sometimes the car goes 'READY' quickly, other times it takes a long time, indicating an intermittent fault.

Verifying the Issue: Diagnosis Steps for Your 2016 Toyota Mirai

Accurately diagnosing the cause of hard starting in your 2016 Toyota Mirai requires a systematic approach. While some initial checks can be done by the owner, a qualified technician with specialized FCEV diagnostic tools will likely be needed for a definitive solution.

1. Check the 12V Auxiliary Battery:
   • Visual Inspection: Look for corrosion on the terminals or any signs of physical damage.
   • Voltage Test: Use a multimeter to check the battery's resting voltage (should be around 12.6V or higher). A load test is even better, as it reveals the battery's ability to maintain voltage under demand. Many auto parts stores offer free battery testing.
2. Monitor Dashboard Warning Lights: Pay close attention to any warning lights that illuminate during the extended startup sequence or remain on afterward. These lights are often accompanied by specific messages in the multi-information display.
3. Listen for Unusual Sounds: During the delay, listen carefully for any abnormal noises from under the hood or beneath the vehicle. These could indicate issues with hydrogen pumps, the air compressor, or cooling fans.
4. Utilize an OBD-II Scan Tool: Although the Mirai is not a gasoline engine, it has an OBD-II port. Connect a capable scan tool to check for Diagnostic Trouble Codes (DTCs). Look for codes related to the fuel cell system (P0Axx, P0Bxx, etc.), high-voltage battery, 12V system, or communication errors. Even if no check engine light is present, pending or historical codes might offer clues. For a comprehensive list of potential issues and repair guides, consider checking all repair guides.
5. Research Technical Service Bulletins (TSBs): Toyota may have issued TSBs for known issues related to the 2016 Mirai's starting system or fuel cell components. A dealership or a specialized FCEV repair shop can access this information. TSBs often provide specific diagnostic steps and repair procedures for common problems.
6. Professional Diagnostic Equipment: A Toyota dealership or an independent shop specializing in FCEVs will have advanced diagnostic tools (like Toyota's Techstream) that can communicate deeply with the Mirai's various ECUs, monitor live data from fuel cell components, hydrogen pressure, and battery states, which is crucial for pinpointing complex issues.

Repair Costs for Hard Starting / Long Crank in a 2016 Toyota Mirai

The cost to resolve hard starting in your 2016 Toyota Mirai can vary significantly depending on the root cause. Here's a general breakdown of potential repair costs:

• 12V Auxiliary Battery Replacement: This is usually the least expensive fix. Costs typically range from $200 - $400, including parts and labor. This is a common maintenance item and a good starting point for diagnosis.
• Hydrogen Pressure Sensor Replacement: If a sensor is faulty, the part itself might be $150 - $400, with labor adding $100 - $300, depending on accessibility. Total: $250 - $700.
• Air Compressor for Fuel Cell: A critical component, replacement can be costly. Parts alone might be $1,000 - $3,000+, with labor adding $400 - $800. Total: $1,400 - $3,800+.
• Fuel Cell System Component Repair (e.g., regulator, injector): These can range widely. A specific component might cost $500 - $1,500 for the part, plus $300 - $700 in labor. Total: $800 - $2,200.
• Power Control Unit (PCU) or Inverter Replacement: This is a major repair. Parts can be $3,000 - $6,000+, and labor can add another $500 - $1,000+ due to the complexity. Total: $3,500 - $7,000+.
• High-Voltage Battery Repair/Replacement: While less common for

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Frequently asked questions

How urgent is this problem?

If symptoms are worsening or safety systems are affected, diagnose soon; minor issues can often wait for a scheduled service visit.

Can I drive with this issue?

Short trips may be acceptable for some faults, but stop driving if you notice overheating, loss of braking, steering problems, or strong fuel smells.

Do I need a dealer scan tool?

A basic OBD-II scanner helps confirm codes; some steps still need visual checks and meter tests described above.

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