Code
P1320
ALFA ROMEO
P — Powertrain
Synchronisation pulse / RPM fault | Timing and RPM synchronisation fault
Views:
UK: 3
EN: 7
RU: 3
AI status
Completed
Completed
100%
Causes
- Faulty crankshaft position (CKP) sensor
- Faulty camshaft position (CMP) sensor or reluctor
- Damaged or corroded sensor connector or wiring (open, short to ground or supply, intermittent)
- Missing or damaged teeth on reluctor/wheel or timing tone ring
- Timing belt / chain skipped or slipped (mechanical timing fault)
- Poor battery voltage or starter signal during cranking
Symptoms
- Check Engine / MIL illuminated
- Hard to start or engine will not start
- Engine stalls shortly after start or during running
- Rough idle, misfires or inconsistent RPM readout
- Intermittent loss of driveability or limp-home mode
- No crank signal shown on scan tool during cranking
What to check
- Read freeze-frame and live data with a capable scan tool; observe crank and cam position signals during cranking and at idle
- Check for presence of P1320 in memory and whether code is pending or confirmed
- Visually inspect sensor connectors and wiring for damage, corrosion, rodent chew, or poor pin fit
- Measure battery voltage and cranking voltage while attempting to start
- Check sensor power (reference) and ground circuits for correct voltages and continuity
- Inspect reluctor/toner ring and timing belt/chain condition and alignment to confirm no skipped teeth
Signal parameters
- CKP/CMP signal types vary by model: Hall-effect (square wave) or variable reluctor (sine/AC) — confirm sensor type before testing
- Hall-effect: expect a clean square wave; amplitude typically referenced to 5 V or battery depending on sensor (0–5 V common for ECU-referenced signals)
- Variable reluctor (VR): AC voltage that increases with engine speed (mV–V range); amplitude near zero at rest, rising with rpm
- Pulse count and reference position vary by engine (single reference tooth per rev, multi-tooth wheel, or missing-tooth patterns) — compare pattern to factory specification
- At idle: engine speed typically 600–900 rpm (engine-specific); signal frequency should be steady and match RPM on scan tool
Diagnostic algorithm
- Verify code and freeze-frame data with scan tool. Note conditions when code set (cranking, running, temperature).
- Check battery and starter voltages; low cranking voltage can corrupt sensor readings—ensure good supply during tests.
- Inspect connectors and wiring to CKP and CMP sensors. Repair any damage, corrosion, or broken pins.
- Using a scan tool, observe live CKP and CMP inputs. If either signal is missing, intermittent or out of phase, suspect sensor, reluctor or wiring.
- If available, use a lab-grade oscilloscope to capture both crank and cam waveforms simultaneously while cranking and running. Look for missing pulses, noise, amplitude problems or timing shift.
- Verify physical timing: remove covers as needed and check timing belt/chain alignment to manufacturer marks to exclude jumped teeth or mechanical timing errors.
- Inspect reluctor/toner ring for damaged, bent or missing teeth and for contamination (metal shavings, debris). Replace or repair as required.
- Test sensor electrical parameters: resistance for VR sensors, supply/reference and ground for Hall sensors, and compare to factory values. Replace sensor if out of spec.
- Repair any wiring faults (shorts, opens, poor grounds). After repairs, clear codes and perform a crank/run verification and road test to confirm issue is resolved.
- If signals and wiring are good but problem persists, verify ECU software and consider ECU testing or replacement as a last resort.
Likely causes
- Wiring/connectors to CKP or CMP sensor are damaged or intermittent
- Crankshaft position sensor has failed (common cause)
- Reluctor ring (toothed wheel) damaged, loose, or contaminated
- Timing chain/belt has jumped teeth (mechanical loss of synchronization)
- Sensor air gap/position out of specification
Fault status
Status
ECU detected missing or inconsistent synchronization pulses between crank and cam sensors (RPM sync fault). May prevent accurate ignition/fuel timing and cause no-start or rough running.
Repair difficulty: Medium
Diagnostic time: 1.0-3.5 hours
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