Why wont my Toyota Highlander start sometimes?

In many cases, intermittent no-starts are caused by electrical power, security-system issues, or fuel delivery problems rather than a simple mechanical failure.

When your Highlander won’t start sporadically, the problem can hinge on a weak 12V battery, a failing starter or alternator, a malfunctioning immobilizer or key fob, a fuel pump or relay issue, or a faulty engine sensor or control module. Environmental factors, corrosion, and worn wiring can also contribute. This article outlines the most common causes, how to recognize them, and practical steps to diagnose or seek help.

Common causes at a glance

These are the issues most likely to cause intermittent starting problems. If you notice any of these symptoms, start with these areas for a quick assessment.

• Weak or dead 12V battery or corroded/loose battery terminals


• Faulty starter motor or solenoid


• I ssue with ignition switch or push-button start


• Immobilizer or key fob problems (dead battery in fob, programming mismatch, or anti-theft start block)


• Fuel delivery problems (empty tank, failing fuel pump, or clogged fuel filter)



• Wiring or ground faults that interrupt power or signal paths

Summary: Intermittent no-starts often point to power, security, or fuel systems. A systematic check of the battery, immobilizer, fuel delivery, and starting circuit is usually required.

Electrical power and starting system

Problems in the electrical side of starting are among the most common reasons a Highlander will refuse to start, especially when symptoms come and go as the vehicle sits or is exposed to temperature changes.

• Battery discharged or aging beyond its capacity to hold a charge


• Corroded or loose battery terminals and poor cable connections


• Bad grounding or wiring corrosion in the engine bay


• Failing alternator or warning light indicating charging problems


• Faulty starter motor or solenoid that cranks inconsistently


• Blown fusible links or relays related to EFI or starter circuits

Conclusion: Electrical issues are often the easiest to diagnose and fix, with battery turnover, clean terminals, and tested relays addressing a large share of intermittent starts.

Security and ignition issues

The Highlander's security system and key recognition play a crucial role in whether the engine allows ignition. Problems here can mimic a dead battery but require different fixes.

• Key fob battery is dead or the fob is not communicating with the vehicle


• Immobilizer not recognizing the key transponder, blocking engine start


• Anti-theft system engaged due to sensor or wiring fault


• Ignition switch failure on older or high-mileage models


• Push-button start sensor or related wiring faults

Conclusion: If the security system is at fault, you may need to replace or reprogram the fob, or address immobilizer communication problems with a dealer or qualified shop.

Fuel delivery and engine management

Fuel delivery problems can prevent starting even when the engine cranks. In modern Highlanders, fuel and engine controls work with sensors and the ECM to decide when to fire the engine.

• Low fuel level or immobilized fuel delivery due to pump failure


• Clogged or dirty fuel filter restricting flow


• Faulty fuel pump relay or blown fuse in the fuel circuit


• Fuel pressure regulator fault or leaking lines


• Dirty or failing fuel injectors affecting spray and combustion

Conclusion: Fuel system issues can cause no-start or intermittent starting, often requiring fuel pressure testing and relay/ fuse inspection to pinpoint the fault.

Sensor and computer issues

Engine sensors and the vehicle’s computer (ECU) govern when the engine should start. Faults here can lead to sporadic no-start conditions or immobilizer-triggered shutdowns.

• Crankshaft position sensor fault or intermittent signal


• Camshaft position sensor fault, affecting timing signals


• Mass air flow (MAF) or manifold absolute pressure (MAP) sensor issues


• ECU software fault or a need for software updates


• Intermittent communication problems between the immobilizer and ECU

Conclusion: Sensor or ECU problems typically require diagnostic codes (OBD-II) and sometimes software updates or component replacement to resolve.

Diagnostics: how to approach this safely

When your Highlander won’t start, a structured approach helps you gather useful information before visiting a shop. Use the following steps as a practical checklist.

1. Note any warning lights, sounds (or lack thereof), and whether the engine cranks or remains completely still.


2. Check the 12V battery voltage with a multimeter (roughly 12.6V when the car is off; 13.7–14.7V when running).


3. Inspect battery terminals for corrosion, looseness, or damaged cables; clean and tighten as needed.


4. Try a spare key or fob to rule out immobilizer or key-related issues; if the vehicle starts with a spare, the original key or fob may need replacement or reprogramming.


5. Verify fuel level and listen for the fuel pump priming sound when the key is turned to accessory or before starting (sound can vary by model year).


6. Use an OBD-II scanner to pull any stored trouble codes and note their meaning for targeted testing.


7. If safe, try jump-starting with a known-good battery; avoid unsafe DIY procedures if you’re unsure.


8. Document symptoms and tests to share with a technician if professional service is needed.

In many cases, addressing the battery, fob, or fuel-delivery symptom resolves the issue, while persistent or unclear symptoms should be evaluated by a qualified technician.

When to seek professional help

Some starting problems require expert diagnosis, especially when repeated tests don’t reveal a clear cause or the issue involves the immobilizer, ECU, or fuel system. Consider professional help if:

• The car cranks but never fires, and basic battery checks are fine


• Warning lights illuminate or diagnostic codes point to ignition, fuel, or sensor faults


• You hear unusual noises, burning smells, or see signs of electrical arcing


• The problem recurs after battery or starter replacement


• Your Highlander is under warranty or subject to a manufacturer recall/TSB investigation

Note: For recall or service bulletin considerations, you can check your vehicle’s VIN on Toyota’s official recall site or consult a dealer for the latest information.

Summary

Intermittent no-start conditions on a Toyota Highlander typically arise from electrical power issues, security/immobilizer malfunctions, or problems with fuel delivery and engine management sensors. A methodical approach—starting with the battery and terminals, then checking the immobilizer and fuel system, followed by diagnostic codes—helps pinpoint the cause. When in doubt, especially if safety concerns or persistent symptoms appear, seek professional evaluation to avoid unnecessary repairs or misdiagnosis.

What is the most common problem with a Toyota Highlander?

The most common problem with the Toyota Highlander is a major oil leak and loss of oil pressure caused by a faulty VVT-i oil line. Other frequent issues include infrequent but noticeable interior rattles, especially from the moonroof or dashboard, and problems with the 8-speed automatic transmission in 2017-2019 models, leading to noises, delayed shifting, and failure. 
You can watch this video to learn about common problems with Toyota Highlander, including the 8-speed transmission issue: 59sChris DrivesYouTube · Jul 5, 2025
Most common problems

• VVT-i oil line rupture: This is the most frequent and serious issue, where the oil line bursts, causing a massive oil leak that can lead to complete engine failure if the vehicle is driven while the low oil pressure light is on. A revised part has been issued, but it has also been reported to have the same problem. 
• Interior rattles and noises: Many owners report various rattles and squeaks coming from the interior, such as the moonroof, dashboard, or infotainment screen, particularly on bumpy roads or in cold weather. 
• 8-speed automatic transmission: Specific models, particularly the 2017–2019 Highlanders, have been associated with issues such as a whining noise, delayed shifts, hard shifts, and even complete failure. 
• Airbag sensor failure: Some models have a faulty front passenger airbag sensor that can short-circuit, preventing the airbag from deploying correctly. 

Other potential issues

• Air and water leaks: Some model years have reported issues with plugged sunroof drain lines, leading to water leaks inside the vehicle. 
• Check engine light: This can be caused by various issues, such as the hose coming off the air filter housing or a failed oxygen sensor. 
• Brake issues: Some models have reported premature wear of brake pads and rotors, or a vibrating sensation when braking. 

This video discusses problems with the 8-speed transmission in the 2017-2019 Toyota Highlander: 58sThe Car Care NutYouTube · Jul 31, 2021

Why does my Toyota have power but won't start?

Ignition System Problems
If the ignition switch, ignition coil, or key fob is malfunctioning, your Toyota may not start. A faulty ignition switch can prevent the car from turning on, while issues with the ignition coil could stop the engine from firing properly.

Why is my Toyota Highlander struggling to start?

Highlander may experience starter motor failure and battery connection corrosion causing starting difficulties. When the engine feels stuck and only half-starts, first check the starter motor and its solenoid for proper engagement. Inspect battery terminals for corrosion or loose connections that reduce power delivery.

Why is my Toyota Highlander not starting sometimes?

When the 2020 Highlander dashboard lights illuminate but the engine won't start, check the starter relay and battery connections first. Even with a new battery, loose or corroded terminals can prevent starting. Inspect the immobilizer system, as a faulty key transponder or security system can disable ignition.