Code
P1321
DAEWOO
P — Powertrain
IG. COIL 4 - PF MAL
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UK: 1
EN: 2
RU: 1
AI status
Completed
Completed
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Causes
- Failed or degraded ignition coil (coil pack/module) at cylinder 4
- Open, shorted or high-resistance wiring/connector to coil #4
- Bad spark plug or spark plug boot/wire at cylinder 4
- Poor ground or battery/charging voltage issue
- Ignition driver (ECU/ignition module) fault
- Moisture, oil or contamination in coil boot or connector
Symptoms
- Malfunction Indicator Lamp (MIL) on
- Rough idle or visible engine shake
- Misfire felt or detected on cylinder 4
- Reduced engine power, hesitation or stumble under load
- Degraded fuel economy and increased exhaust emissions
- Possible difficulty starting or intermittent misfire
What to check
- Read stored codes and freeze-frame data with OBD-II scanner
- Note pending/related codes (misfire codes like P0304) and freeze frame conditions (RPM, load, voltage)
- Visual inspection of coil #4, connector, wiring harness and coil boot for damage, oil or moisture
- Inspect and check spark plug condition for cylinder 4; replace if fouled or worn
- Swap ignition coil #4 with another cylinder’s coil and see if code/misfire follows the coil
- Measure coil primary and secondary resistance and compare to spec
Signal parameters
- Coil primary resistance (ohms) — compare to spec
- Coil secondary resistance (kΩ) — compare to spec
- Battery voltage at coil connector (V) — key on/crank
- Ignition primary waveform: dwell time (ms), primary current/voltage peaks (use oscilloscope)
- Misfire counts (cylinder 4) and P0304 presence
- Engine RPM and load during fault/freeze frame
Diagnostic algorithm
- Retrieve and record P1321 and any additional codes (e.g., P0304). Capture freeze-frame data.
- Clear codes and perform a controlled road/idle test to try to re-create the fault and confirm persistence.
- Perform visual inspection: coil #4, connector pins, wiring harness, coil boot and spark plug for oil, carbon tracking or damage.
- Swap coil #4 with a known-good coil from another cylinder. If the fault/misfire follows the coil, replace the coil.
- If swap does not move the fault, remove coil and inspect spark plug; replace spark plug if out of spec or fouled.
- Measure coil primary and secondary resistance and compare to manufacturer specification. If out of spec, replace coil.
- Backprobe coil connector with oscilloscope or DVOM during cranking/run: verify proper supply voltage, switching signal from ECU, dwell and primary waveform. Look for weak or absent primary pulses or abnormal waveform shapes.
- Check continuity and resistance of the wiring between coil connector and ECU. Repair damaged wires or corroded terminals.
- If wiring and coil are good but no proper driver signal from ECU, inspect ignition driver/ECU outputs and grounds; consult wiring diagrams. Consider ECU diagnosis or replacement only after confirming external components are good.
- After repairs, clear codes and verify by running engine under the conditions that previously set the fault. Confirm no return of P1321 and that misfire counters are normal.
Likely causes
- Faulty ignition coil pack/module for cylinder 4
- Corroded/loose connector or pin to coil #4
- Worn or fouled spark plug in cylinder 4
- Damaged secondary lead/boot (if applicable)
- Open/short in primary coil wiring between coil and ECU
- Faulty ignition driver transistor inside ECU (less common)
Fault status
Status
P1321 — Ignition Coil 4 malfunction detected (primary/secondary fault). MIL on; fault stored. Verify coil, wiring, plug and ECU driver.
Repair difficulty: Medium
Diagnostic time: 0.5–2.0 hours
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