What the camshaft position sensor (CMP) does — in plain terms
- Purpose: the CMP tells the engine computer (ECU) exactly where the camshaft is in its rotation. The ECU uses that information to time fuel injection (and sometimes ignition) for each cylinder. Think of the CMP as a lighthouse or a conductor’s baton that tells the engine “now cylinder 1 is ready” so the right injector or ignition event happens at the right instant.
- Why a repair is needed: if the CMP fails or the signal is wrong, the ECU can’t properly time fuel delivery. Symptoms: hard/no start, long cranking, rough/uneven idle, loss of power, poor fuel economy, stalling, and a check-engine light with camshaft-related trouble codes (P0340, P0341, P0016, etc.). On diesel Toyotas (1HZ / 1PZ / 1HD-T) incorrect cam info affects injector timing and turbo management, so drivability is noticeably worse.

Which components are involved (detailed)
- Camshaft position sensor (CMP)
- Types: two common designs —
- Hall-effect (3-wire): reference 5V, ground, and a digital signal (square wave 0–5V).
- Variable reluctance / magnetic (2-wire): coil that generates an AC voltage as the reluctor (target) passes.
- Physical parts: sensing element, plastic/aluminum body, mounting flange, O-ring or rubber seal, connector.
- Connector and wiring harness
- Connector housing, male/female pins, locking clip, wiring to ECU. Pins carry power, ground, signal.
- Mounting hardware
- Sensor mounting bolt(s), sometimes spacer, and a locating boss in the head or timing cover.
- Reluctor / trigger wheel (cam timing plate)
- A metal tooth, notch or plate mounted on the camshaft or cam sprocket that passes the sensor. Its shape and spacing create the waveform/impulses the sensor detects.
- Engine control module (ECU)
- Reads the CMP signal, compares it to the crankshaft position sensor (CKP) signal, and controls injection timing. If signals disagree, ECU may set codes or enter limp/baseline mode.
- Crankshaft position sensor (CKP)
- Works with CMP. The CKP gives engine speed and a primary reference; CMP provides cylinder phase so ECU can sequence injectors or adjust timing.
- Seals and gaskets
- O-rings and seals keep oil out of the connector area; a failed O-ring can short the sensor or corrode pins.

How the system works (simple step-by-step)
1. Mechanical: a reluctor on the camshaft passes the sensor once per cam revolution (cam turns once every two crank revolutions on a 4-stroke engine).
2. Sensing:
- For Hall sensors: the sensor gets a 5V reference and ground from the ECU. When the reluctor aligns, the sensor pulls the signal to ground or lets it go high, producing a square wave pulse. Each pulse corresponds to a known cam position (for example, cylinder 1 TDC intake).
- For VR sensors: the rotating reluctor induces an AC voltage in the sensor coil proportional to speed; the ECU conditions and counts those pulses.
3. ECU function: the ECU compares cam pulses to crank pulses, determines cylinder phase and exact timing, and instructs injectors or adjusts fuel-pump timing accordingly.
Analogy: CKP = a clock’s second hand (fast and continuous), CMP = a minute hand telling you which hour you’re in (which cylinder stroke). Both together tell time precisely.

What can go wrong (fail modes and their causes)
- Sensor electrical failure
- Internal electronics burned (overheat / age), magnet weakened, coil open/shorted.
- Connector/wiring faults
- Corroded pins, oil intrusion, broken wires, chafed insulation, poor ground, or pin pushed out.
- Mechanical wear/damage
- Broken or missing teeth on the reluctor, loose reluctor, sensor mounting boss worn so sensor misreads.
- Oil contamination or coolant intrusion
- O-ring failure lets oil into connector causing shorts or corrosion.
- Heat/engine vibration damage
- Plastic cracking, broken leads, intermittent signal when hot.
- Timing phase shift
- If cam timing (belt/chain) has jumped or worn, the sensor signal will be out of expected phase relative to crank — ECU will detect mismatch and set codes even if sensor itself is OK.
- ECU problems
- Rare, but bad ECU input circuits or wrong reference voltages will mimic sensor failure.

Symptoms that indicate CMP trouble
- Engine cranks but won’t start, or very hard to start.
- Misfires, rough idle, poor acceleration, reduced power.
- Check Engine Light and codes related to camshaft position signal or timing correlation.
- Intermittent stall or failure that sometimes returns to normal (classic sign of wiring/connector intermittent).
- No or weak voltage signal from sensor when tested.

How to diagnose (basic tests for a beginner)
1. Visual inspection first
- Inspect connector for corrosion, bent pins, oil, or dirt. Wiggle the harness while watching for changes.
- Inspect O-ring and mounting area for oil leaks.
2. Read fault codes
- Use an OBD2 / Toyota scanner. Codes like P0340/P0341 indicate CMP signal problems or correlation issues with CKP.
3. Identify sensor type by wire count
- 3 wires = Hall (reference, ground, signal). 2 wires = VR (coil only).
4. Electrical tests (engine OFF then cranking test as needed)
- Hall (3-wire):
- With ignition ON (engine not running): backprobe reference wire — you should see ~5V (some ECUs use 12V; check manual). Check ground continuity to engine ground.
- While cranking, backprobe signal: you should see switching between near 0V and near reference (or a pulsing waveform) — easiest to see with a scope, but a multimeter may show a fluctuating voltage.
- VR (2-wire):
- Measure resistance across the two pins (engine cold). A healthy VR coil typically has a few hundred ohms (specs vary). If open or infinite, it’s bad.
- While cranking, measure AC voltage across the two pins — you should see pulses proportional to cranking speed (0.2–1 V AC at idle/crank, more with higher rpm). An oscilloscope is best.
5. Wiggle test
- With key on or cranking, gently wiggle the harness at the connector to see if signal drops (intermittent wiring).
6. Check for correct phase with CKP
- If both sensors produce signals but ECU reports correlation fault, timing may have slipped (timing belt/chain), or the reluctor is misaligned.

How to remove and replace a CMP sensor (general steps — common to Toyota diesels)
Tools needed: basic metric socket set, ratchet, extension, small flat screwdriver or pick, multimeter (or scope), dielectric grease, light penetrating fluid (if stuck), torque wrench if available, protective gloves, safety glasses.

Preparations
- Park on level ground, engine off and cool. Remove key.
- Disconnect negative battery terminal if you prefer; many technicians replace CMP with battery connected but for safety some disconnect battery.
- Clean area around sensor to prevent debris falling in.

Remove sensor
1. Locate sensor — usually mounted on the cylinder head or timing cover near the camshaft/cam sprocket. (Exact placement varies by engine model/year.)
2. Unplug the connector: press the locking tab and pull apart. If pins are corroded, clean with contact cleaner.
3. Remove the mounting bolt(s) — typically a single 8–12 mm bolt. Keep it safe.
4. Twist gently while pulling sensor straight out. It may be sealed with an O-ring — twisting loosens it. If stuck from grime or corrosion, spray penetrating oil around base, allow time, then ease out. Protect surrounding plastic parts when prying.
5. Inspect the sensor tip and reluctor area for metal shavings, oil, scoring, or damaged teeth.

Install new sensor
1. Compare new sensor to old one: same length, same connector, same number of pins.
2. Lightly lubricate the O-ring with clean engine oil or dielectric grease to ease installation and seal.
3. Insert sensor straight into the boss until seated. Do not force or over-rotate.
4. Torque the mounting bolt to the manufacturer spec. If you don’t have spec, snug it evenly — typically small bolts are 6–12 Nm (~5–9 ft-lb). Don’t over-tighten.
5. Reconnect connector; ensure locking clip engages.
6. Reconnect battery if you disconnected it.
7. Clear ECU codes with a scanner or allow ECU to reset (key ON then OFF several seconds, or drive cycle). Crank engine to check for start and proper idle.
8. Test drive and verify symptom resolution and no new codes.

Testing after replacement
- Scan for pending codes. If code persists, check wiring continuity to ECU and CKP signal correlation.
- If possible, monitor live data (CMP signal frequency or waveform) while cranking and at idle. A steady square wave for Hall sensors and consistent amplitude AC for VR sensors is expected.

Torque and sealing cautions
- The sensor’s O-ring is important — do not leave it dry or damaged. Replace O-ring if sensor comes with one.
- Avoid over-torquing the bolt (plastic bosses and small bolts strip easily).

Troubleshooting special cases
- Intermittent faults: usually wiring harness or connector corrosion. Replace harness section or repair with solder/heat-shrink, secure with conduit.
- Codes persist after sensor replacement:
- Check CKP sensor and its waveform (a mis-synced crank sensor will still set cam correlation faults).
- Check cam timing (belt/chain jumped a tooth).
- Inspect reluctor/trigger wheel for missing or damaged teeth.
- No signal but sensor tests good off-engine: likely harness wiring open between sensor and ECU, blown fuse, or bad ECU input.

Safety and best practices
- Always keep engine off and cool for removal. Be careful around belts/pulleys if working with the front of engine exposed.
- Avoid pulling wiring — disconnect at connector rather than yanking harness.
- Mark or photograph connections before removing if there are multiple similar connectors.
- Use dielectric grease sparingly on connectors to prevent corrosion but not inside the sensor where it would contaminate the sensing face.

Quick troubleshooting flow (one-page mental map)
1. Visual inspect connector/harness → clean/correct obvious faults.
2. Read ECU codes.
3. Identify sensor type (2-wire VR or 3-wire Hall).
4. Test power/ground (Hall) or resistance (VR).
5. Backprobe signal while cranking (scope ideal).
6. Replace sensor if signal faulty or intermittent.
7. If signal OK but codes persist, check CKP and cam timing.

Final notes specific to Toyota 1HZ / 1PZ / 1HD-T line
- These are diesel engines where correct cam/crank correlation is critical for injector timing. The exact sensor location and pinout can vary by model year — location is typically on the cylinder head/timing cover near the camshaft. Always verify the correct replacement part number for your engine and year.
- If you suspect the timing belt/chain has jumped, do not simply replace the CMP and drive — confirm mechanical timing before running the engine under load.

That’s the complete beginner-friendly overview: what each component is and does, how the system functions, common failures, how to test and replace the sensor, and what to watch for after repair.
rteeqp73

Land cruiser 1HZ 1HDT 1PZ Valve shim adjustment tutorial A "how to" on how to adjust the valve shims on your toyota land cruiser with 1HZ and 1HDT engine, but will work on other as well.

Land cruiser 1HZ 1HDT 1PZ Valve shim adjustment tutorial A "how to" on how to adjust the valve shims on your toyota land cruiser with 1HZ and 1HDT engine, but will work on other as well.

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