Code
P1334
DAEWOO
P — Powertrain
#4 MISFIRE CIRCUIT - OPEN
Views:
UK: 3
EN: 3
RU: 1
AI status
Completed
Completed
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Causes
- Open or broken wiring in coil/igniter primary circuit for cylinder 4
- Poor or corroded connector or pin at the coil/igniter or wiring harness
- Failed ignition coil or coil-on-plug assembly for cylinder 4
- Faulty ignition driver (igniter) or ignition module
- Power supply (fused source) or ground open to the coil bank
- Intermittent/loose ECM/PCM connector or internal driver fault in ECM/PCM
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Rough idle or vibration at idle
- Reduced engine power or hesitation under load
- Single-cylinder misfire count for cylinder 4 in scan data
- Poor fuel economy and possible failed emissions test
- Occasional cranking/no-start if circuit is fully open
What to check
- Read freeze frame and live data — confirm misfire count for cylinder 4
- Visual inspection of coil/igniter, connector, wiring harness and pins for damage/corrosion
- Check for battery voltage at coil power feed with ignition ON
- Check continuity and resistance of coil primary and secondary circuits
- Swap coil (or coil/igniter) from cylinder 4 with another cylinder and rerun to see if fault follows
- Backprobe coil connector while cranking with a scope or lab meter to verify driver pulses
Signal parameters
- Expected coil primary resistance: typically ~0.5–3.0 ohms (manufacturer-specific)
- Expected coil secondary resistance: typically ~3k–15k ohms (manufacturer-specific)
- Coil power feed: battery voltage (~12 V) with ignition ON (should remain present)
- Coil driver signal: pulsed 0–12 V (or low-side switching to ground) while cranking/running — visible on a scope as dwell pulses
- Open-circuit indication: no driver pulses and/or infinite/open continuity on primary circuit
Diagnostic algorithm
- Connect a scan tool, read DTCs and freeze-frame; confirm P1334 and verify misfire logs show cylinder 4.
- Perform a careful visual inspection of the #4 coil/igniter, plug and wiring harness. Look for broken wires, rubbed-through insulation, melted connectors or corrosion.
- With ignition OFF, disconnect the coil connector and check terminal condition and continuity to the ECM connector. Wiggle the harness while checking for intermittent opens.
- Check for battery voltage on the coil power feed with ignition ON; verify good engine/chassis ground present at coil bracket/harness ground.
- Measure coil primary and secondary resistance against manufacturer specs; if out of range, replace the coil.
- Swap the #4 coil (or coil-on-plug) with a known-good coil from another cylinder. Clear codes and run engine; if misfire/DTC moves to the other cylinder, the coil is faulty.
- If coil appears good, backprobe the coil primary while cranking or running with a scope or digital meter to verify driver pulses from the PCM. No pulses indicates open or driver fault.
- If driver pulses are absent but wiring continuity from PCM to coil is OK, suspect PCM/ignition module driver fault. Confirm wiring and grounds before replacing control module.
- Repair any damaged wiring, connectors, or replace faulty coil/igniter. Clear codes and perform a test drive to confirm repair.
- If intermittent, perform wiggle tests and road test with data logging to reproduce the fault before replacing components.
Likely causes
- Damaged connector or wiring harness to cylinder 4 coil
- Failed coil or integrated igniter on cylinder 4
- Blown fuse or open power feed to ignition coils
- Poor ground at engine/coil bracket or harness ground
- ECM/PCM driver fault (less common)
Fault status
Status
Cylinder 4 ignition/misfire circuit open. PCM detected loss of ignition driver/continuity for cylinder 4 causing a misfire. Check coil, connector, wiring, power/ground and PCM driver.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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