OBD-II Code · Ignition
P0350
Ignition Coil Primary/Secondary Circuit
Severity
high
Left alone, this one tends to take other parts with it.
Can you drive it
Not for long
Driving on this one risks further damage. Get it to a shop rather than carrying on with it.
Indicative cost (USD)
$0–$600
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
Generic ignition coil circuit fault — shared power/ground/ICM problem.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Multi-cylinder misfire
- No-start
- Check engine light
Likely causes
- Failed ICMMost common
- Corroded coil ground
- Cracked coil-pack housing
- Bad ASD relay
Read the full diagnostic procedureP0350 means the ECM detected a primary or secondary circuit fault in an ignition coil but couldn't isolate which specific coil — it's the generic 'so…
P0350 means the ECM detected a primary or secondary circuit fault in an ignition coil but couldn't isolate which specific coil — it's the generic 'something's wrong on the coil driver side' code, usually thrown on older OBD-II systems (pre-2000) that lack per-cylinder coil monitoring, or on modern systems when the fault is shared across multiple coils (common ground, common 12V feed, or ignition module).
Cheapest-first diagnostic
- start at the coil power feed — key-on-engine-off, backprobe the B+ pin on any COP connector and confirm 12.0-12.6V with the engine off and 13.5-14.5V cranking; a reading under 10V cranking points to a corroded ignition relay, blown coil fuse, or voltage-drop in the harness ($5-$25 fix).
- Next, check the coil ground — voltage drop from coil ground pin to battery negative should be under 0.1V under load; anything over 0.3V means a corroded ground stud (clean and torque, $0 fix).
- Only after power and ground are clean do you scope the primary trigger signal from the ECM (looking for a clean 0-12V square wave at idle, ~6-10ms dwell) and measure secondary coil resistance (typical primary 0.4-2.0 ohms, secondary 6,000-15,000 ohms depending on platform).
- Don't condemn a coil pack on resistance alone — many coils fail only under load and read fine cold on a meter, so a power-balance test or scope capture is the real proof.
Vehicle-specific patterns1996-2000 GM 3.1L/3.4L V6 with the ICM-mounted-under-coil-pack design throws P0350 when the ignition control module fails — the symptom is intermitte…
- 1996-2000GM 3.1L/3.4L V6 with the ICM-mounted-under-coil-pack design throws P0350 when the ignition control module fails — the symptom is intermittent no-start hot, and the fix is the $80-$140 ICM under the coil pack, not the coils themselves.
- 1996-1999Ford 4.6L 2V with the rear-mounted DIS coil pack throws P0350 from cracked coil-pack housings letting moisture in; pull the pack, look for hairline cracks on the tower side.
- 1998-2003Dodge/Jeep 4.7L early SOHC V8 throws P0350 from a failed ASD (auto shut-down) relay or chafed 12V feed running across the intake manifold — wiggle-test the harness with the engine running.
- 2000-2004Toyota Tundra/Sequoia 4.7L 2UZ-FE with the original Denso COPs is famous for whole-bank P0350 events when the shared coil-side ground strap on the rear of the head corrodes — clean and retorque before buying eight coils.
Estimated repair$0 (clean ground) to $600 (full coil set + ICM).
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P0350 — frequently asked
What does a P0350 code mean?
Generic ignition coil circuit fault — shared power/ground/ICM problem.
What causes a P0350 code?
Common causes: Failed ICM; Corroded coil ground; Cracked coil-pack housing; Bad ASD relay.
What are the symptoms of a P0350 code?
Typical symptoms: Multi-cylinder misfire; No-start; Check engine light.
Is it safe to drive with a P0350 code?
Not for long. Driving on this one risks further damage. Get it to a shop rather than carrying on with it. Estimated repair: $0-$600.
How do I diagnose a P0350 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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