Code
P1346
CADILLAC
P — Powertrain
Intake Camshaft Position (CMP) Sensor System Performance
AI status
Completed
Completed
100%
Causes
- Faulty intake camshaft position (CMP) sensor
- Damaged or corroded CMP connector or wiring (open, short to power/ground, high resistance)
- Poor sensor reference voltage or ground
- Noisy or missing CMP signal due to failed sensor type (Hall or VR)
- Incorrect camshaft timing (stretched timing chain/belt, slipped sprocket, misinstalled timing)
- Failed or sticking VVT/cam phaser or oil control valve (phaser stuck, low oil pressure or dirty oil)
Symptoms
- Check Engine Light (MIL) on, code P1346 stored
- Rough idle or intermittent misfire
- Hard starting, long crank or no-start condition in some cases
- Reduced engine power or limp mode
- Poor fuel economy and increased emissions
- Possible abnormal engine noise if timing chain or phaser mechanical issues present
What to check
- Use a scan tool to read freeze frame data, pending codes and live CMP/CKP PID data
- Confirm code is current vs. historic; clear codes and attempt to reproduce under similar conditions
- Visually inspect CMP sensor connector, wiring harness and pin condition for corrosion, damage, chafing or oil intrusion
- Verify battery voltage, PCM ground(s) and sensor reference voltage presence at CMP connector
- Backprobe sensor connector and capture waveforms from CMP and CKP simultaneously with an oscilloscope or high‑speed data recorder
- Check sensor resistance (for VR type) and compare to spec, or check for a 5V (or 12V) reference and square wave output (for Hall type)
Signal parameters
- Hall-effect CMP: reference 5V (or 12V), square wave output 0–5V with clean switching edges; switching threshold ~2–3V
- Variable Reluctor (VR) CMP: AC sine wave amplitude increases with engine speed (hundreds of mV to volts) and frequency proportional to RPM
- Signal frequency: proportional to engine speed — expecting consistent pulse spacing and amplitude at idle and with increasing RPM
- Phase/correlation: CMP pulse position must align with CKP pattern per manufacturer-specific tooth/marker relationship — timing offset beyond PCM tolerance triggers performance codes
- Noise: excessive jitter, missing pulses, or irregular amplitude indicate wiring, sensor fault, or magnetic interference
Diagnostic algorithm
- Read frozen data, note engine conditions when the code set (RPM, temp, load). Clear codes and attempt to re-create under same conditions.
- Visually inspect CMP sensor, harness, and connector for damage, oil, corrosion, or bent pins. Repair as needed.
- With key ON engine OFF, verify reference voltage and ground at the sensor connector. For Hall sensors expect ~5V reference; for VR verify continuity to PCM ground.
- Backprobe sensor while cranking and/or running. Capture CMP waveform and simultaneously capture CKP waveform on an oscilloscope. Look for consistent amplitude, clean edges (Hall), or consistent sine wave (VR), and correct phase relationship to CKP.
- If CMP signal absent or erratic, measure sensor resistance (VR) and compare to spec or substitute a known-good sensor to confirm diagnosis.
- If sensor signals are good but PCM reports correlation fault, inspect timing components: confirm cam timing marks, check timing chain/belt condition and tension, and inspect phaser/VVT actuator operation (apply oil pressure or use bidirectional control if supported).
- Check for oil contamination or low oil pressure that can cause phaser sticking; inspect and test VVT solenoid and oil passages.
- Repair or replace faulty sensor, repair wiring/connectors, correct mechanical timing or phaser issues. After repair, clear codes and road test while monitoring CMP/CKP signals to confirm proper operation.
- If all wiring, sensor and mechanical timing checks pass and the fault persists, consider PCM software update or replacement as a last step.
Likely causes
- Failed CMP sensor
- Broken/shorted wiring or poor connector pin contact
- Cam phaser/variable valve timing not operating (often due to low oil pressure or sludge)
- Timing chain/belt jump or worn sprocket causing cam/crank correlation error
Fault status
Status
P1346 — Intake Camshaft Position (CMP) Sensor System Performance: PCM detected missing, erratic or out‑of‑tolerance intake camshaft position signal or poor CMP/CKP correlation.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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