Code
P1324
HUMMER
P — Powertrain
Crank RPM Too Low
Views:
UK: 18
EN: 35
RU: 28
AI status
Completed
Completed
100%
Causes
- Weak or discharged battery
- Poor battery connections, corroded terminals or ground(s)
- Faulty or slow starter motor
- Damaged or missing crankshaft reluctor/tone ring (tooth damage or missing teeth)
- Faulty crankshaft position (CKP) sensor (open/short/intermittent)
- Damaged wiring or connector to CKP sensor (opens, shorts, high resistance)
Symptoms
- Engine cranks slowly or does not crank at all
- Engine fails to start even though starter turns
- No or very low RPM displayed on scan tool during cranking
- Check Engine Light (MIL) set and P1324 stored
- Intermittent starting or stalling
- Misfires or rough idle if engine does start
What to check
- Verify customer complaint and conditions when code set (cranking, starting, running)
- Scan for additional DTCs and freeze frame data
- Check battery voltage at rest and during cranking (use a digital voltmeter)
- Inspect battery terminals and engine grounds for tightness and corrosion
- Perform a starter draw/current test if cranking is weak
- Monitor crankshaft RPM and CKP sensor waveform with a scan tool and oscilloscope while cranking
Signal parameters
- CKP sensor type: Hall-effect (square wave, typically 0–5V) or magnetic pickup (AC sine, amplitude varies with speed) depending on model year
- Expected signal: clean, regular pulses corresponding to teeth on reluctor at idle/cranking; no missing pulses
- Typical cranking RPM threshold: manufacturer-specific (many systems expect >~150–300 RPM during cranking)
- Idle/run RPM thresholds: ECM expects stable RPM in normal idle range (often ~600–900 rpm); low RPM fault triggers if below configured limit
- Voltage during cranking: battery voltage typically 9–12V under load; if below ~8–9V many sensors/ECM inputs may behave erratically
Diagnostic algorithm
- Record conditions and scan tool data: capture DTCs, freeze frame and live data for crank RPM during cranking/starting.
- Check battery state: measure open-circuit voltage and voltage while cranking. Recharge or replace battery if low or fails load test.
- Inspect battery positive/negative terminals and engine/body grounds; clean and tighten as needed.
- Test starter operation: perform starter current draw and bench test if suspect. Repair/replace starter as needed.
- Using an oscilloscope or lab scope, probe CKP sensor signal at sensor and at ECM pin while cranking. Look for consistent pulses, correct amplitude and no missing teeth.
- If CKP signal weak or missing at sensor: inspect sensor air gap, mounting, reluctor condition (missing/bent teeth, debris). Replace or repair as needed.
- If CKP signal present at sensor but absent at ECM: inspect wiring and connector continuity, short-to-power/ground, and repair harness/connector faults.
- If wiring and sensor are good, check related fuses, power and ground circuits to ECM and sensor. Verify ECM reference voltage and input circuits.
- Perform compression test and engine mechanical checks if you suspect mechanical seizure or timing jump (e.g., broken timing chain/belt).
- If all components test good, consider ECM diagnostics or reflash and consult manufacturer service info before ECM replacement.
- Clear codes and perform test start cycles to verify repair; monitor for recurrence and capture new data if code returns.
Likely causes
- Battery state-of-charge or high internal resistance
- Loose/corroded battery negative cable or engine ground
- Starter draw excessive or starter not engaging
- CKP sensor failure or weak signal (intermittent or low amplitude)
- Reluctor/tone wheel damage, oil/metal debris on sensor gap
- Broken/shorted wiring harness or poor sensor connector contact
Fault status
Status
MIL illuminated; P1324 stored in ECM memory. Engine may crank slowly or fail to start. Additional drivability symptoms possible depending on root cause.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
Repair manuals
Manual library for HUMMER
69
Browse 69 HUMMER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.
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