About the photograph. The engine below is a 2010 Toyota Yaris 1.5L with its cosmetic cover still fitted, which is how you will first see it. Several of the sensors sit underneath that cover or below the intake manifold runners, so the numbers mark where to look rather than a part you can see in the picture. Each write-up below gives you the landmarks to find the sensor itself once the cover is off.
- Fuel injectors (located on the front side of the engine near the intake manifold)
- Mass airflow sensor (MAF)
- Camshaft position sensor (CMP) (located at the rear of the cylinder head cover)
- Oil pressure switch (located behind intake manifold near CKP)
- Knock sensor (KS) (located on the front of the engine under the intake manifold)
- Crankshaft position sensor (CKP) (located on the side of engine under intake manifold)
- Engine coolant temperature sensor (ECT) (located at the rear of engine)
- Ignition coils (located under cover on top of cylinder head cover)
- Air Fuel Ratio Sensor (AFRS) (located in the exhaust manifold)
- Electronic Throttle Body / Throttle position sensor (TPS)
- Camshaft Oil Control Valve (front top of cylinder head cover)
- Manifold Absolute Pressure sensor (MAP) (located next to throttle body)
3. Camshaft Position Sensor (CMP)
Monitors the rotational position of the intake camshaft to identify cylinder firing order and provide critical VVT-i feedback to the ECM. The ECM pairs this signal with crankshaft position data to verify valve timing synchronization, optimize Variable Valve Timing (VVT-i) operation, and trigger sequential fuel injection. Sensor faults typically result in an illuminated check engine light, poor fuel economy, sluggish throttle response, or hard starting.
Where it is. The camshaft position sensor, number 3 in the list above, is located on the driver-side rear corner of the aluminum cylinder head cover. It mounts directly into the upper side of the head cover casting, positioned adjacent to the main wiring harness bracket. Look for a compact plastic sensor with a black 2-pin electrical connector angled upward.
Getting at it. Replacement is an easy 10-to-15-minute job requiring only a 10mm socket or box wrench. Workspace access at the top-rear of the cylinder head is wide open, requiring no removal of intake components or protective engine covers.
Codes: DTC P0340 or P0341 indicates a camshaft position sensor circuit malfunction or phase correlation fault.
Fitting it. Inspect the rubber sealing ring on the new sensor to ensure proper seating against the valve cover bore. Lightly coat the O-ring with fresh engine oil before inserting the probe into the cylinder head, and avoid using any RTV sealant on the plastic body. Tighten the single 10mm hold-down bolt until snug (7.5 ft-lb / 10 Nm), taking care not to strip the soft aluminum threads in the cylinder head.
How it typically fails. Continuous thermal exposure at the top of the cylinder head causes the plastic housing to harden and crack over extended periods, allowing moisture to enter the internal circuitry and cause intermittent signal loss or drop-outs. Always gently wiggle the sensor back and forth to break the seal before pulling it outward, as prying on a hardened plastic flange can snap the mounting tab.
5. Knock Sensor (KS)
Detects high-frequency mechanical vibrations caused by pre-ignition or engine detonation (“pinging”) within the cylinders. The sensor generates a micro-voltage signal that prompts the ECM to retard ignition timing to protect internal engine components like pistons, connecting rods, and crankshaft bearings from severe or sometimes fatal mechanical damage. Sensor faults typically cause sluggish performance, reduced power under heavy load, and noticeably decreased fuel efficiency as the ECM reverts to a conservative timing and fuelling strategy.
Where it is. The knock sensor, number 5 in the list above, is mounted directly into the center of the engine block casting beneath the intake manifold runners on the front side of the engine. Look for a round, flat piezo-electric sensor secured by a central stud, featuring a single-wire or two-wire harness connector facing toward the driver side.
Getting at it. Replacement is a moderately difficult 30-to-45-minute task requiring a 12mm deep socket, a medium extension, and a ratchet. Access can be tight between the intake manifold runners, though removing the intake manifold is generally not required if working from underneath or using a swivel socket extension.
Codes: DTC P0325 indicates a primary knock sensor circuit malfunction.
Fitting it. Proper surface preparation is crucial; scrub the engine block mounting surface clean of rust or debris to ensure proper metallic contact for accurate vibration transfer. Thread the sensor onto the mounting stud and torque it to factory specification (approx. 15 ft-lb / 20 Nm); improper torque settings can alter the sensor’s frequency response, which may result in persistent false knock codes.
How it typically fails. Over extended periods, engine heat cycling and exposure to engine bay moisture eventually degrade the internal piezoelectric crystal and damage the sensor’s outer casing. Inspect the wiring pigtail closely for brittle or cracked insulation, as high engine temperatures near the block frequently cause wiring failures near the connector plug.
6. Crankshaft Position Sensor (CKP)
Monitors the precise rotational speed and position of the crankshaft to provide the Engine Control Module (ECM) with essential primary timing signals. The ECM uses this frequency data to calculate engine RPM, determine exact piston position, detect misfires, and synchronize ignition spark timing with fuel delivery. Sensor failures typically lead to extended engine cranking times, hard starting, engine hesitation or stumbling under acceleration, random engine stalling at low engine speeds, or a crank-no-start condition.
Where it is. The crankshaft position sensor, number 6 in the list above, is located on the front lower face of the engine block, tucked underneath the plastic intake manifold runners near the crankshaft pulley. Look for a dark plastic cylindrical body mounted flush into the engine block casting, featuring a single mounting tab and a 2-pin electrical locking connector.
Getting at it. Replacement is a moderately difficult 20-to-30-minute driveway job requiring a 10mm socket, a small ratchet, and a short extension. Reaching the mounting bolt requires reaching down between the front intake manifold runners or working from underneath the front bumper area after removing the lower plastic splash shield.
Codes: DTC P0335 or P0336 indicates a primary crankshaft position sensor circuit malfunction or range/performance issue.
Fitting it. Clean all road grime and oil residue from around the mounting hole before removing the old sensor to prevent dirt from dropping directly into the timing chain cover area. Apply a thin film of clean engine oil to the sensor’s rubber O-ring prior to installation to ensure a positive seal without binding or pinching. Secure the 10mm mounting bolt by hand first, then torque it lightly to approximately 7.5 ft-lb (10 Nm); over-tightening can easily crack the plastic mounting ear.
How it typically fails. Over extended periods, exposure to engine vibrations, heat cycling, and road splash cause the internal electromagnetic pickup coil to break down, often resulting in an open circuit before the engine reaches full operating temperature. Inspect the female harness connector for broken locking tabs or oil contamination, as poor electrical connections often mimic a failing sensor pickup.
7. Engine Coolant Temperature Sensor (ECT)
Measures engine coolant temperature to provide vital thermal data to the ECM for fuel mixture calculation, ignition timing adjustment, radiator fan control, and dashboard gauge display. When the engine is cold, the ECM uses ECT inputs to enrich the air-fuel mixture; as the engine warms up, it leans out the mixture to optimize engine performance and reduce emissions. Sensor faults typically lead to poor idle quality when the engine is cold, excessive fuel consumption, or radiator fan malfunctions.
Where it is. The engine coolant temperature sensor, number 7 in the list above, is located on the rear driver-side portion of the cylinder head, situated in the main coolant outlet housing near the upper radiator hose connection. Look for a brass-bodied sensor with a green or black 2-pin electrical connector screwed directly into the coolant passage.
Getting at it. Replacement is a straightforward 20-minute driveway job requiring a 19mm deep socket or open-end wrench. Drain roughly a half-gallon of coolant from the radiator drain cock prior to removal to prevent coolant from spilling over the bell housing and surrounding electrical connectors.
Codes: DTC P0115, P0117, or P0118 indicates an engine coolant temperature circuit error, such as low or high input conditions.
Fitting it. Clean the female threads in the coolant housing before installing the new component. Apply a small wrap of PTFE tape or thread sealant to the male brass threads, taking care to leave the bare sensor tip clean and fully exposed to the coolant flow. Thread the sensor in by hand to prevent cross-threading the aluminum threads, then tighten firmly with a wrench without over-torquing the brass hex.
How it typically fails. Over extended periods, internal thermistor breakdown or coolant corrosion can alter the sensor’s resistance curve, causing it to report incorrect temperature values to the ECM without necessarily setting error codes. Inspect the electrical connector for green copper corrosion or coolant wicking inside the socket, which indicates the internal seals have failed.
Models Found on Beginning In 2008:
- Toyota Yaris/Echo
- Scion xA/Toyota ist
- Scion xB
- Toyota Raum
- Toyota Porte
- Toyota Platz
- Toyota Auris
- Toyota Fun Cargo
- Toyota Premio
- Toyota Allion
- Toyota Corolla
Where is number 12 on the picture? Its not there.