Code
P1312
DAEWOO
P — Powertrain
IG. COIL 2
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UK: 1
EN: 5
RU: 2
AI status
Completed
Completed
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Causes
- Failed ignition coil (coil pack or coil-on-plug) for cylinder 2
- Open or shorted wiring in the coil 2 primary or secondary circuit
- Poor or corroded connector or pins at the coil
- Faulty ignition coil driver in the engine control module (ECM/PCM)
- Damaged or fouled spark plug on cylinder 2
- Intermittent ground or battery supply to the coil circuit
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Rough idle and engine vibration, especially at idle
- Reduced engine power, hesitation or stumbling under load
- Engine misfire focused on cylinder 2 (possible P0302)
- Hard starting or extended cranking in some cases
- Poor fuel economy and increased emissions
What to check
- Read freeze-frame and stored data; confirm P1312 and note conditions (rpm, temp, load)
- Confirm related codes (e.g., P0302, P0352) before repairing
- Visually inspect coil 2 and connector for corrosion, moisture, cracks or damage
- Wiggle test harness with engine running (careful) to look for intermittent faults
- Swap coil 2 with another cylinder's coil (if identical) — see if fault follows the coil
- Measure coil primary and secondary resistance with a multimeter and compare to spec
Signal parameters
- Coil primary resistance (typical): approx. 0.3–2.0 ohms (refer to vehicle spec)
- Coil secondary resistance (typical): approx. 5 k–15 k ohms (refer to vehicle spec)
- Supply voltage at coil connector: battery voltage (~11–14 V) with key ON/engine cranking
- Primary trigger pulse: square/digital pulse from ECM; amplitude near battery voltage on primary side when switching
- Secondary spark voltage: varies widely (kV) depending on plug gap and load; absence or weak waveform indicates problem
Diagnostic algorithm
- Connect a scan tool, read DTCs and freeze-frame data. Note related misfire or coil codes.
- Perform visual inspection of coil 2, connector and wiring for damage, corrosion or oil/water intrusion.
- With key OFF, disconnect coil connector and inspect pins for corrosion or bent terminals. Repair or clean as needed.
- Measure coil primary and secondary resistance against factory specifications. Replace coil if out of range.
- With key ON (engine OFF) verify battery voltage at the coil power terminal and good ground at the connector.
- If accessible and safe, swap coil 2 with another identical cylinder coil. Clear codes and run to see if code follows coil (if it follows, replace coil).
- If the fault remains on cylinder 2 after swap, check wiring continuity between ECM and coil connector for opens/shorts and repair harness as needed.
- Use an oscilloscope to observe primary ignition waveform while cranking/running. Look for missing pulses, abnormal dwell, or flatlined primary signal.
- Inspect/replace spark plug for cylinder 2 and confirm correct gap and condition.
- If wiring and coil check good but problem persists, test or consult procedures for ECM ignition driver; replace ECM only after confirming external circuit is good.
- Clear codes, perform functional/road test and monitor for recurrence. Re-scan for stored or pending codes.
Likely causes
- Defective coil-on-plug unit for cylinder 2
- Loose/corroded coil connector or pin causing intermittent contact
- Open/short in the harness between ECM and coil 2 (chafing, rodent damage)
- Failed ECM ignition driver for cylinder 2 (less common)
- Bad spark plug causing excessive coil stress or weak spark
Fault status
Status
Ignition coil circuit fault for cylinder 2 detected. This may cause misfire and MIL illumination. Inspect coil, connector, wiring and ECM driver before replacing major components.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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