Summary: below is an ordered, compact explanation of what a camshaft position (CMP) sensor does, how to diagnose its failure, a safe step‑by‑step replacement procedure for a Toyota B / 2B family engine, and why the repair fixes the fault. No extra chit‑chat.

1) Theory — what the camshaft position sensor does and how it works
- Purpose: the CMP sensor tells the engine control unit (ECU) the camshaft angular position (top‑dead‑center reference and cylinder identification). ECU uses it with the crankshaft sensor to time fuel injection and (on petrol engines) ignition, and on diesels to control injection events and sequencing.
- Types: two common types:
- Hall‑effect/active sensor: requires a reference voltage (typically 5 V or the ECU supply), uses an internal semiconductor to switch output between reference and ground as a ferrous target/reluctor passes; output is a square pulse (0→Vref).
- Variable reluctance/passive coil: a small coil generates an AC voltage as a toothed reluctor passes; amplitude/frequency proportional to shaft speed.
- Signal use: the ECU compares cam pulses with crank pulses to determine engine phase. Missing, intermittent, delayed, or noisy cam signals lead to mis‑timing, misfires, limp mode, poor idle, hard start/no start, and stored diagnostic trouble codes (DTCs).

2) Common symptoms and diagnostics (ordered)
- Symptoms: Check Engine Light and DTCs (P0340/P0341 or manufacturer codes), hard starting, no start, rough idle, loss of power, misfire codes, erratic fuel trim, limp mode.
- Scan for codes first; note freeze frame data and live data (cam sensor pulse, cam/crank correlation).
- Quick bench checks:
- Hall sensor: with ignition ON, measure reference pin ~5 V (or ECU supply), ground continuity, and output toggling to ground while cranking (or use a scope).
- Passive sensor: measure coil resistance (Ω) cold — compare to spec (if unknown: few ohms to hundreds depending), and check AC output while cranking (use a scope or AC voltmeter).
- Wiggle test: backprobe connector while running/cranking; intermittent change indicates harness/connector problem.
- Inspect connector for corrosion, bent pins, oil contamination, and wiring for chafing or breaks.
- If diagnostics point to the sensor and wiring is good, replacement is next.

3) Tools & safety (brief)
- Tools: basic metric sockets (8/10/12 mm commonly), ratchet, torque wrench, screwdriver, small pick for connector, dielectric grease, replacement CMP sensor (OE or quality aftermarket), multimeter or scope for verification.
- Safety: engine off and cool, disconnect negative battery terminal before connector removal if working near electrical circuits; avoid rotating engine with sensor removed unless explicitly required by procedure; support vehicle properly if lifting; wear eye protection and gloves.

4) Replacement procedure — ordered steps
Note: exact location/fastener sizes can vary. On Toyota B / 2B engines the CMP is on the cylinder head/timing cover at the camshaft end; consult the factory manual for exact access and torque specs. Use these ordered steps as the logical sequence.

1. Prepare
- Park on level ground, set parking brake, switch ignition OFF, remove key.
- Let engine cool if hot.
- Disconnect negative battery terminal to avoid shorts (optional for quick sensor swaps, but recommended).

2. Locate sensor
- Find CMP sensor on the front/top of the cylinder head/timing cover near camshaft. Identify connector and mounting bolt(s).

3. Access & clear area
- Remove obstructing components (air intake duct, engine cover, wiring bracket) as needed for clearance.
- Clean around the connector to prevent dirt falling into openings.

4. Disconnect electrical connector
- Depress the locking tab, gently pull connector straight off. Do not pry pins. Inspect connector for oil/corrosion.

5. Remove mounting bolt(s) and sensor
- Remove the sensor mounting bolt(s) with the appropriate socket.
- Carefully twist/pull the sensor straight out. Note any O‑ring/seal — inspect it; replace if brittle or damaged.

6. Compare old/new sensor
- Verify new sensor matches mounting, connector and trigger geometry. Transfer any O‑ring or use new one.

7. Install new sensor
- Lightly lubricate new O‑ring with clean engine oil or dielectric grease as specified; seat sensor straight into bore.
- Install bolt(s) finger tight, then torque to manufacturer spec (typical small sensor bolts: ~6–12 N·m; use factory spec if available).
- Reconnect electrical connector until it clicks.

8. Reassemble removed parts
- Reinstall intake duct, covers, loosened brackets.

9. Reconnect battery
- Reconnect negative battery terminal.

10. Post‑fit checks
- Clear DTCs with scan tool.
- Start engine and observe: should start normally and idle smoothly.
- Monitor live cam sensor data on scanner or use oscilloscope to check waveform while cranking and at idle. Verify stable pulse, correct frequency and amplitude.
- Test drive to ensure symptoms resolved and no reappearance of codes.

5) How the repair fixes the fault (clear, in‑order explanation)
- Fault mode: a bad CMP sensor (open, shorted, intermittent, or producing erroneous waveform) provides no/incorrect cam position information to the ECU.
- Consequences: ECU cannot determine cylinder phase reliably → incorrect injector timing or ignition timing sequencing → misfires, rough idle, hard/no start, limp behavior, and stored DTCs.
- Repair action: replacing the sensor restores the correct electrical/mechanical interface:
- The new sensor produces a clean, correctly timed electrical pulse (Hall or AC) synchronized to cam rotation.
- The ECU receives accurate cam timing relative to the crankshaft and can calculate correct injector timing and ignition advance, and correctly identify cylinder sequencing for sequential fuel/injection events.
- If the original fault was connector/wiring corrosion, cleaning/replacing the connector restores signal integrity and ground/reference continuity.
- Result: stable signal eliminates timing errors, clears misfire/start issues, normalizes trims and restores engine performance and drivability.

6) Verification tests to confirm successful repair (ordered)
- Scan tool: confirm no cam‑related fault codes stored and live cam position data present.
- Waveform: observe a clean, repeatable square wave (Hall) or consistent AC pulses (reluctor) with correct relation to crank pulses.
- Drive: normal start, smooth idle, no limp mode, restored power, no recurrence of symptoms.

Quick troubleshooting notes (concise)
- If new sensor shows no output: check reference voltage, ground, and wiring continuity to ECU before condemning the new sensor.
- Intermittent faults often indicate wiring or connector issues rather than the sensor itself; always inspect harness and grounding.

End.
rteeqp73

TIPS - VALVE LASH ADJUSTMENT ON TOYOTA B AND 3B DIESEL ENGINE Video show how to adjust valve clearances on a Toyota B/2B/3B diesel engine.

How to Diesel Engine 1B 2B 3B 14B Pump timing Easy Installation diesel engine 1B 2B 3B 14B pump timing Easy installation You can adjust the static fuel injection timing by adjusting the shim ...

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