Code
P1336
HUMMER
P — Powertrain
Crankshaft Position (CKP) System Variation Not Learned
AI status
Completed
Completed
100%
Causes
- CKP sensor failure (noisy, intermittent, open, short)
- Damaged or missing reluctor/tone wheel teeth or incorrect reluctor installed
- Wiring harness or connector corrosion, damage, or poor grounding
- Battery discharged or low system voltage during relearn
- PCM/ECM lost learned adaptation after power loss or replacement
- Required relearn procedure not performed after replacing sensor, reluctor, or PCM
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated with P1336 stored
- Difficulty starting, extended cranking or no-crank/no-start in some conditions
- Intermittent stalling, rough idle, or poor drivability
- Misfires or reduced engine performance
- Engine cranks but no ignition/timing reference resulting in no spark (depending on system)
- Codes related to crank/cam correlation or CKP circuit may be present
What to check
- Retrieve freeze frame and all stored/PENDING trouble codes; note any related CKP/CMP or PCM codes
- Verify battery voltage and charging system health (>= 12.4 V at rest, >=13.5 V running)
- Inspect CKP sensor connector and harness for corrosion, bent pins, damaged insulation, or chafing
- Visually inspect tone wheel/reluctor for missing/bent teeth, rust, or debris; verify correct reluctor installed
- Confirm no recent service (battery, PCM, timing components) that would require a relearn
- Perform a wiggle test on wiring while cranking to reproduce signal loss
Signal parameters
- CKP sensor types: Hall/optical -> digital square wave (approx. 0–5 V logic signal); VR (magnetic) -> AC sine signal (typically 0.1–1.5 VRMS at idle, increasing with RPM)
- Signal must be clean, stable, and proportional to engine speed; no excessive noise, dropouts, or irregular pulse widths
- Reference/power to sensor (if active type) typically ~5 V or 12 V depending on vehicle — verify with service manual before testing
- Pulse pattern: fixed number of teeth/markers per engine revolution; missing or extra pulses indicate tone wheel damage or incorrect reluctor
Diagnostic algorithm
- Connect a capable scan tool and confirm P1336 is current (not pending); record freeze frame and related codes
- Check battery voltage and charging system; charge or replace battery if low and retest
- Visually inspect CKP sensor and tone wheel for physical damage, correct installation, and magnetic debris; repair or replace if found
- Inspect sensor connector and harness for corrosion, broken wires, shorts to ground or power; repair wiring harness or connector faults
- Measure sensor supply/reference and ground (if applicable) using DVOM; compare to OEM specification
- Use an oscilloscope (preferred) or lab scope to capture CKP waveform while cranking and at idle; look for consistent amplitude, clean edges (Hall), or stable AC amplitude (VR) and correct pulse count/pattern
- If waveform is poor or absent, replace CKP sensor or repair wiring; retest waveform after repair
- Perform the manufacturer-specified CKP system variation relearn/CKP variation learn procedure with a scan tool (required after sensor/PCM replacement or loss of learned values) and follow the exact steps and engine conditions
- Clear codes, perform a key-on/engine-start relearn sequence if applicable, then test drive or run engine through required RPM range to confirm no return of code
- If relearn fails and wiring/sensor verified good, consider PCM reflash or replacement per service information only after exhausting sensor and wiring checks
Likely causes
- Failed or marginal CKP sensor
- Poor or missing CKP signal due to damaged tone wheel or magnet
- Open/short/corroded wiring or poor sensor ground
- Failed relearn after battery disconnect or module replacement
- Incorrect timing or mechanical fault causing inconsistent crank reference
Fault status
Status
Crankshaft Position system variation not learned — CKP variation relearn required. Can cause no-start or rough operation until relearned.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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