Code
P1337
DAEWOO
P — Powertrain
#7 MISFIRE CIRCUIT - OPEN
Views:
UK: 1
EN: 3
RU: 1
AI status
Completed
Completed
100%
Causes
- Open or broken wiring between ECM and ignition coil/coil pack for cylinder 7
- Disconnected, corroded, or damaged coil connector
- Failed ignition coil or coil pack
- Blown fuse or power supply failure to coil circuit
- Faulty ECM/ignition driver pin for cylinder 7
- Aftermarket wiring or recent repair left open circuit
Symptoms
- Check Engine Light (MIL) illuminated
- Rough idle or vibration, especially at idle
- Reduced engine power and poor acceleration
- Increased fuel consumption and higher emissions
- Misfire detected specifically on cylinder 7 (P0307 may also be stored)
What to check
- Read and record DTCs and freeze frame data with a scan tool; note MIL state and related codes
- Visually inspect wiring and connector for coil 7 for damage, corrosion or disconnection
- Check for blown fuses and correct power/ground at coil supply circuits
- Backprobe coil 7 connector to check for battery voltage on supply pin with ignition ON
- Use a scope or multimeter to check for coil driver switching (pulse to ground) while cranking
- Measure coil 7 primary and secondary resistance and compare to spec
Signal parameters
- Coil supply voltage: ~11–14 V with ignition ON (vehicle battery voltage)
- Coil primary resistance: typically 0.3–3 Ω (manufacturer spec required)
- Coil secondary resistance: typically 5 kΩ–20 kΩ (manufacturer spec required)
- ECM driver output: pulsed to ground while cranking/running (use scope to verify)
- No continuity/OL on primary or open circuit indicates open/faulty coil or wiring
Diagnostic algorithm
- Retrieve all stored codes and freeze frame data. Note any other ignition or crank/cam sensor codes.
- Visually inspect the coil 7 area: connector, wiring harness, insulation, and mounting. Repair obvious damage.
- With ignition OFF disconnect coil 7 connector and inspect pins for corrosion or bent pins. Reconnect securely.
- With ignition ON, backprobe the coil supply terminal to confirm battery voltage present. If no supply, trace fuse/relay and power circuit.
- With a proper scope or multimeter, crank engine and verify the ECM pulses the coil driver (switches to ground). No pulse suggests ECM or open/in-line break.
- Measure coil primary and secondary resistance on the removed coil. If open or out of spec, replace coil and retest.
- Perform a swap test: replace coil 7 with coil from another cylinder. If misfire/code moves with coil, replace coil. If it stays on cylinder 7, suspect wiring/ECM.
- If wiring suspect, disconnect battery, check continuity between coil connector and ECM pin. Repair any open, high-resistance joints or damaged wiring.
- If wiring and coil are good and supply/pulse present but code persists, test or replace the ECM/ignition driver only after confirming all upstream wiring and sensors are functional.
- After repairs, clear codes and perform a road/idle test to confirm no recurrence and that misfire counts return to normal.
Likely causes
- Damaged harness (chafing, pinched, rodent damage) to coil 7
- Loose or corroded connector at coil 7
- Failed coil (open primary or internal open circuit)
- Open circuit between coil connector and ECM
- Blown ignition-related fuse or relay feeding coil bank
Fault status
Status
ECM detected an open circuit in the cylinder 7 ignition/misfire control circuit (no continuity or driver signal). Code stored; MIL set. Freeze frame and misfire counters may be available.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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