Toyota Yaris: common faults & what to check

Symptoms to notice

• Engine suddenly stops or misfires severely in heavy rain or after driving through water
• Engine will not crank or cranks with a heavy knocking sound after a water event
• Water present in the intake pipe or airbox after rain
• Catastrophic misfire with bent rod confirmed on teardown

What to check

1. 1.Inspect the air intake path from the wheel arch to the airbox for any signs of water ingestion (watermarks inside the intake pipe, corroded or wet filter).
2. 2.Ask owner if an aftermarket snorkel or intake relocation kit has been fitted — this is a widely recommended modification for GR Yaris owners in NZ.
3. 3.Ask if the car has ever been driven through water or in very heavy rain.

Symptoms to notice

• Blue or grey smoke from exhaust on startup or hard acceleration
• Oil level consistently low at next service despite no external leaks
• Fouled or oil-coated spark plugs on cylinder inspection
• Oil consumption warning or low-oil pressure light illuminating

What to check

1. 1.Watch for: Blue or grey smoke from exhaust on startup or hard acceleration.
2. 2.Check oil dipstick level and condition; inspect exhaust on cold start for blue smoke; remove and inspect all spark plugs for oil fouling; check PCV hose and valve for blockage or collapse; query owner on frequency of oil top-ups between services.

Symptoms to notice

• AWD system or drivetrain warning light illuminated on dashboard
• Loss of rear-wheel drive engagement feel during acceleration
• Unexpected clunking or vibration from rear drivetrain under load
• Drivetrain mode selector defaulting to front-wheel drive only
• Diagnostic fault codes relating to rear coupling actuator motor circuit

What to check

1. 1.On a test drive with the drivetrain mode in Sport or Track, perform a moderate acceleration from standstill on a loose or wet surface and feel for rear torque delivery.
2. 2.Verify no AWD or drivetrain warning lights are present.
3. 3.Ask the seller for dealer service history confirming GR-FOUR software update completion.

Symptoms to notice

• Humming or droning noise from the front differential that worsens during cornering
• Vibration felt through the floor at highway speeds, not linked to engine RPM
• Front differential fluid appearing dark brown or smelling burnt at inspection
• Clunking from the front drivetrain during low-speed tight turns
• Noise increasing progressively with accumulated mileage

What to check

1. 1.During the test drive, listen at highway speed for a humming or droning noise that changes pitch with vehicle speed rather than engine speed, and note whether it intensifies during left or right turns.
2. 2.Check differential fluid condition — dark, burnt-smelling fluid indicates overheating or a missed service.
3. 3.Confirm the differential fluid has been changed on Toyota's recommended schedule.

Symptoms to notice

• Vibration or shudder felt through the drivetrain when pulling away from rest
• Shudder may be worse when cold or at light throttle openings
• Hesitation or slip sensation between 20–40 km/h
• Condition may temporarily improve then return with heat cycles

What to check

1. 1.Test drive from cold and perform multiple slow-speed pull-aways in a carpark.
2. 2.Note any vibration or judder at low speed or when the transmission is hunting.
3. 3.Check CVT fluid condition if accessible — dark or burnt-smelling fluid indicates overdue service.
4. 4.Ask when CVT fluid was last changed.

Symptoms to notice

• Clutch slipping under hard acceleration — engine revs rise without corresponding vehicle acceleration
• Clutch bite point abnormally high on the pedal stroke
• Burning friction material smell from the clutch after spirited driving
• Clutch chatter or judder during slow take-off from rest
• Sudden total loss of drive in severe pressure plate spring fracture cases

What to check

1. 1.On a test drive, engage third gear at approximately 2500 RPM then apply firm acceleration — any clutch slip will be revealed by RPM rising without a matching increase in vehicle speed.
2. 2.Note the bite point height on the pedal: a bite point very high near the top of travel indicates disc wear.
3. 3.Smell for burnt friction material after a firm test drive.

Symptoms to notice

• Vibration or shudder felt through the floor during light throttle acceleration
• Shudder most pronounced when pulling away gently from a standstill
• Audible juddering or chattering noise from beneath the vehicle
• Symptom may reduce or disappear once CVT reaches full operating temperature

What to check

1. 1.Drive the vehicle from cold, applying light throttle from rest and note any vibration through the floor or drivetrain.
2. 2.Check CVT fluid condition, colour, and service history.
3. 3.Confirm Toyota Genuine CVTF FE fluid has been used, not a generic substitute.

Symptoms to notice

• Metallic rattling or clattering from engine front on cold start, typically clearing after 2 to 5 seconds
• Chain rattle that worsens progressively over time or at higher mileages
• Check Engine light with OBD codes P0016 or P0017 (cam/crank correlation fault)
• Rough idle or hesitation during cold-start warm-up phase
• Increased oil consumption alongside rattle onset

What to check

1. 1.Cold-start the engine from fully cold and listen immediately at the front of the engine for a metallic rattling or clattering lasting 1 to 5 seconds.
2. 2.Check oil level and condition on the dipstick — dark dirty oil indicates neglected service intervals that accelerate tensioner wear.
3. 3.Request complete service records verifying oil changes at or below 10,000 km intervals.

Symptoms to notice

• Vibration or judder felt through drivetrain at light throttle between 40–70 km/h
• Shudder disappears under hard acceleration or when coasting
• Jerky or hesitant gear engagement from a standing start
• Transmission fluid that is dark, burnt-smelling, or past its service interval

What to check

1. 1.Drive the vehicle at steady light throttle between 40–70 km/h and feel for a rhythmic vibration through the floor or seat.
2. 2.Inspect the transmission fluid level, colour, and smell — dark or burnt fluid on an XP90 Yaris indicates neglect.
3. 3.Ask for transmission service history.
4. 4.Early intervention with a fluid change and friction modifier additive can resolve shudder if the clutch friction material is not yet worn.

Symptoms to notice

• Reduced boost pressure and noticeably lower power output under load
• Higher intake air temperatures than expected if monitored via OBD
• ECU-imposed boost and timing reductions triggered by elevated intake temps
• Check Engine light with codes relating to boost or charge air temperature limits
• Pump completely silent when it should be audible or turning when checked manually

What to check

1. 1.With the engine running and warm, locate the charge cooler pump in the intercooler coolant circuit and confirm it is running (audible low hum or vibration when touched).
2. 2.Check for any stored fault codes relating to intercooler temperature or boost control limits.
3. 3.Ask the seller whether any reduction in power or throttle response has been noticed during warm weather or sustained driving.

Symptoms to notice

• Metallic rattling or chattering from the timing chain area for 2–5 seconds immediately after a cold start, disappearing once oil pressure builds
• Oil consumption above 0.5 L per 5,000 km accompanied by rattle, indicating tensioner and guide rail wear progressing together

What to check

1. 1.Cold-start the engine and listen at the timing cover for a metallic rattle lasting more than 1 second.
2. 2.Check engine oil level and condition — low or degraded oil accelerates tensioner bleed-down.
3. 3.Request service history to confirm oil change intervals under 7,500 km.
4. 4.Remove the oil filler cap and inspect for sludge, which blocks the tensioner feed gallery.

Symptoms to notice

• Metallic rattling noise from the front of the engine on cold start
• Rattle subsides within 5 to 15 seconds as oil pressure fully builds
• Noise is notably louder in cold weather or after the vehicle sits overnight
• Check engine light may illuminate if timing has shifted due to chain wear

What to check

Cold-start the vehicle from a fully cold state and listen immediately at the engine front for chain rattle from the timing cover. Verify oil level on the dipstick and review oil service history for correct intervals and grade. If a workshop inspection is possible: Use an OBD scanner to check for any stored timing or camshaft position fault codes.

Symptoms to notice

• Rattling or clattering from top of engine for 1–3 seconds on cold start
• Noise disappears immediately after oil pressure builds
• Intermittent rough idle in cold conditions before warm-up
• Check Engine light for variable valve timing fault codes (P1349)

What to check

1. 1.Start the engine cold and listen carefully from outside the vehicle; rattle from the top-front of the engine near the cam cover indicates VVT-i sprocket wear.
2. 2.Check for stored fault codes P1349 or P1354.
3. 3.Inspect oil condition — contaminated oil accelerates damper wear.

Symptoms to notice

• Rough or lumpy idle particularly when engine is cold
• Hesitation or stumble on light throttle from low engine speeds
• Noticeable reduction in power output relative to when the car was new
• Intermittent misfire fault codes in P030x range
• Slightly increased fuel consumption compared to rated figures

What to check

1. 1.Ask specifically about carbon induction cleaning history.
2. 2.Note any rough idle when cold, hesitation on light throttle inputs, or intermittent misfire — all indicate significant deposit accumulation.
3. 3.If a workshop inspection is possible: If a borescope is available, inspect through the intake ports for black carbon buildup on the valve heads.

Symptoms to notice

• Noticeably reduced fuel economy compared to the rated specification
• Hybrid battery warning triangle illuminated on dashboard
• State-of-charge gauge swings rapidly between extremes or sits persistently low
• Combustion engine running continuously at low speeds where it should be off
• EV-only mode unavailable or cutting out almost immediately

What to check

1. 1.Verify no hybrid system warning lights are present on the dashboard.
2. 2.On a 20-minute test drive including a section of urban stop-start driving, observe how frequently the combustion engine kicks in at low speed — battery degradation forces the ICE to run far more than on a healthy pack.
3. 3.Request a Toyota dealer hybrid battery health report; examples older than 8 years should be treated as likely requiring battery reconditioning or replacement.

Symptoms to notice

• EPS or power steering warning light illuminated on dashboard
• Sudden increase in steering effort, particularly at low speed or parking
• Intermittent return of normal steering assist then loss again
• Fault stored in EPS control module (retrievable via OBD scan)

What to check

1. 1.Check the dashboard for any stored EPS warning light.
2. 2.Turn the steering lock-to-lock slowly at idle and note any inconsistency in assist level.
3. 3.Inspect under the dashboard for signs of water ingress or moisture near the steering column base.
4. 4.If a workshop inspection is possible: Scan the EPS control module with an OBD tool for fault codes C1511–C1555.

Symptoms to notice

• Driver window switch feels sticky or works intermittently
• Burning smell or heat from the driver door switch
• Window switch stops working

What to check

Ask for the window switch recall paperwork and check the VIN with a Toyota dealer. Operate every window from the driver's switch several times, feel the switch for heat and smell for burning plastic. If a workshop inspection is possible: the switch panel can be removed to look for melted or scorched contacts.

Symptoms to notice

• Visible condensation or standing water inside one or both taillight lenses, particularly noticeable after rain or washing
• Intermittent brake light, indicator, or tail light failure that does not correspond to a blown bulb, caused by corroded bulb holder contacts creating an open or resistive circuit

What to check

1. 1.Inspect the taillight lenses for visible condensation or water droplets inside the lens.
2. 2.Check all rear light functions including brake, indicator, and reverse — any intermittent operation points to corroded contacts.
3. 3.Inspect the body-to-lens seal (typically foam rubber) for compression set, cracking, or gaps.
4. 4.If a workshop inspection is possible: Remove the taillight assembly and inspect the bulb holders for green or white corrosion on the contacts and heat discolouration on the plastic holder from arcing.

Symptoms to notice

• Sudden onset of severe rear tyre scrubbing or uneven wear on one side, caused by a deformed or cracked beam altering rear toe angle
• Cracking or popping sound from the rear underbody under cornering load or when driving over sharp bumps, distinct from bush noise

What to check

Pay particular attention to the upper weld bead on each side. Check for uneven rear tyre wear which can indicate the beam has deformed. If any crack is visible this is an immediate reject — the car must not be driven. This inspection is especially important on any NCP90 that has been used for towing or has high annual mileage. If a workshop inspection is possible: On a hoist, clean the weld areas where the trailing arms meet the central beam tube and inspect with a torch for cracking, rust bubbling, or separation.

Symptoms to notice

• Brake pedal slowly sinks toward the floor under sustained firm pressure during a static hold test, even though no external fluid leak is visible
• Brake fluid reservoir level gradually dropping over weeks without any visible leaks at callipers, hoses, or wheel cylinders, indicating internal bypass to the booster side

What to check

1. 1.With the engine off, depress the brake pedal firmly and hold constant pressure for 30 seconds — any pedal sinking more than 5 mm indicates internal bypass.
2. 2.Check brake fluid in the reservoir for dark brown or contaminated condition, which accelerates seal degradation.
3. 3.Inspect the master cylinder body and both brake lines at the master for weeping.
4. 4.Ask when the brake fluid was last flushed — the service interval is every 2 years regardless of appearance.

Symptoms to notice

• No symptom until the airbag deploys
• Airbag warning light on

What to check

1. 1.Ask the seller for the airbag recall paperwork, and check the VIN with a Toyota dealer or the government recall check before you buy.
2. 2.Look for a recall completion sticker in the door jamb or under the bonnet, and check the airbag warning light comes on at start up then goes out.
3. 3.If a workshop inspection is possible: a Toyota dealer can confirm by VIN whether the replacement inflator has been fitted.

Symptoms to notice

• ABS warning light permanently illuminated on the dashboard without any wheel speed sensor fault being present
• Brake pedal pulsing during normal braking below ABS activation threshold, indicating a solenoid valve sticking open due to internal corrosion

What to check

1. 1.Visually inspect the ABS modulator for white corrosion deposits and rust staining around the solenoid connectors and brake line unions.
2. 2.Scan for ABS codes C0200 (right front wheel speed sensor circuit) or C1241 (ABS solenoid malfunction) which can be triggered by modulator corrosion rather than sensor failure.
3. 3.Check whether the ABS warning light is permanently illuminated on the dashboard.
4. 4.Request previous WOF history — repeated ABS advisory notes indicate an ongoing problem.

Symptoms to notice

• Spongy or unusually hard brake pedal feel
• Greater than normal pedal force required to achieve adequate braking
• Hissing noise from engine bay when pressing the brake pedal
• First press of the brake pedal after startup feels noticeably different to subsequent presses

What to check

With engine off, pump the brake pedal 5 times to exhaust stored vacuum, then start the engine and press the pedal firmly. Normal operation gives a clear drop in pedal height as vacuum is restored. Inspect all vacuum hoses for cracks, splits, and secure connections.

Symptoms to notice

• Clunking or thumping from the front suspension over bumps, speed bumps, and during braking, often described as coming from the front corners
• Steering wander or vague straight-line tracking that worsens under braking, caused by the control arm pivot shifting under load

What to check

On a road test, accelerate and brake firmly in a straight line and listen for a thud or clunk from the front suspension, which worsens on broken surfaces. If a workshop inspection is possible: With the vehicle on a hoist, grip each front lower control arm and attempt to move it fore-aft and vertically — any visible rubber delamination or more than 2 mm of play indicates bush failure. Check for cracking of the outer rubber visible without disassembly.

Symptoms to notice

• Front seat slides or rocks slightly after locking it
• Seat slide lever feels loose

What to check

Ask for the seat recall paperwork and check the VIN with a Toyota dealer. Sit in each front seat, lock it and push hard forward and back: it should not move. If a workshop inspection is possible: the seat track lock mechanism can be checked with the seat removed.

Symptoms to notice

• Knocking or rattling sound from the steering column when making small steering inputs at low speed, such as lane changes or parking
• EPS warning light appearing intermittently, sometimes accompanied by momentarily heavy steering before the system resets

What to check

With the engine running (EPS active), slowly oscillate the steering wheel 5–10 degrees either side of centre and listen for a knock or rattle from the column below the dash. Check the instrument cluster for the EPS warning light (orange steering wheel icon). Pull the steering wheel gently fore-aft to feel for column shaft end-play. If a workshop inspection is possible: Scan with an OBD reader for EPS-specific codes C1511 or C1512 (torque sensor signal out of range).

Symptoms to notice

• Handbrake lever travels very high before brakes engage, more than 8 clicks
• Vehicle rolls on a slope with handbrake fully applied
• WoF failure for insufficient parking brake holding force
• Rear brake pedal feels long or spongy compared to front

What to check

Apply the handbrake and count the number of clicks before full engagement; more than 7-8 clicks is a concern. Check WoF records for any brake-related advisories or failures. If a workshop inspection is possible: Remove rear drum covers if possible and inspect adjuster mechanism for corrosion, seizure, and spring integrity.

Symptoms to notice

• Persistent petrol smell in the engine bay particularly noticeable after the engine reaches operating temperature and is shut down
• Visible fuel staining or wet residue at the base of one or more injectors where they seat into the intake manifold, sometimes with accumulated carbon and dirt stuck to the fuel

What to check

A fuel smell that is strongest at the manifold (not from the cap or filler) is diagnostic. Clean the area with brake cleaner before inspection to make fresh weeping clearly visible. This fault is most common on engines over 150,000 km or those that have not had injectors removed during prior service. If a workshop inspection is possible: With the engine warmed up and then shut off, remove the engine cover and check around the base of each injector where it enters the intake manifold for fuel staining, wet deposits, or glistening.