P0350: How to Diagnose & Fix — Ignition Coil Primary/Secondary Circuit Malfunction
2 vehicles · 2 makes · $120-$700 repair
How to diagnose and fix P0350: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Nissan 300ZX · 1990–1996
The Z32's external ignition power transistor unit (igniter), mounted in the hot engine bay, degrades internally with age and heat — early 'Series 1' units have failing solder joints and internals that act up as the unit heat-soaks. A failing PTU causes intermittent rough idle, sudden stalling while driving (often only once the engine is hot), or a crank-no-start that resolves after the unit cools, and the unsealed connector corrodes and produces the same symptoms. Because the car can cut out without warning in traffic, owners treat a suspect PTU and its connector as a priority fix; NHTSA complaints for the 1990 car include hot-weather stalling that clears when the car cools (ODI 856214).
Common Symptoms
- Engine stalls without warning once fully warmed up
- Cranks but will not start when hot, starts again after cooling down
- Idle speed wanders or changes intermittently
- Intermittent total ignition cut or hesitation under load
- Green corrosion on the PTU connector pins
How to Fix
Replace the PTU with the updated later-style Nissan unit (sold as a kit with the adapter subharness for early cars), and clean and dielectric-grease the corroded connector terminals while you're there. Skilled DIYers can re-solder failed Series 1 internals, but replacement is the accepted fix.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Updated Nissan Z32 power transistor unit (PTU)
1990+ Z32 using the updated Nissan PTU wiring configuration; an early Series 1 car needs the separate adapter subharness unless already converted. Check campaign history first.
- Nissan Z32 Series 2 PTU adapter subharness
1990-1996 Z32 as described by seller, but purchase only for an early-style PTU connector/conversion branch; not needed when the recall/campaign conversion harness is already present. Fitment/availability: In stock and add-to-cart live at…
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Sources for this issue (7)
- Power Transistor Unit Issues - NICOclub Nissan Forumsforum
- OEM Nissan 300ZX (Z32) Power Transistor (PTU) Kit - Z1 Motorsportsmanufacturer
- A handy guide to fixing series 1 PTU's (Power Transistor Unit) - 300ZX Owners Clubforum
- 90 300zx crank but will not fire (HELP Z FRIENDS!) - NissanForumsforum
- NHTSA 1990 Nissan 300ZX complaints (ODI 856214 hot-weather stalling, verified via complaints API)nhtsa
- How to solve engine hesitation and stumble problems on the 90+ 300ZX (zhome.com, PTU soft-fail and US recall noted)article
- Nissan OEM Power Transistor Unit PTU Series 2 Kit - Nissan 300ZX Z32 - Specialty-Zmanufacturer
Kia Rio · 2001–2011
Across both generations of Rio, owners frequently report ignition-related misfires caused by failing coil packs, deteriorated plug wires on earlier cars, or worn spark plugs. The problem typically shows up as rough idle, hesitation under load, flashing MIL, and poor fuel economy. It is common enough in owner complaints and repair forums to be considered a recurring Rio issue, especially as these cars age.
Common Symptoms
- check engine light
- flashing MIL
- rough idle
- hesitation on acceleration
- engine shaking
- poor fuel economy
How to Fix
Scan for cylinder-specific misfire codes, inspect plugs for wear or oil fouling, and test or swap coils to isolate the fault. On early models, replace aged plug wires along with plugs; on later coil-on-plug setups, replace the failed coil and inspect the connector for corrosion. If misfires persist, check for vacuum leaks and compression issues before replacing more parts.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- A-Premium APIC1312 ignition coil, plug and wire kitOEMA-Premium APIC1312 / PartsGeek 655-03080396
Replace diagnosed worn early-generation coil/wires and plugs as a matched service kit Fitment/availability: 2001-2002 Kia Rio 1.5L Base/Cinco/RX-V and 2003-2005 Rio 1.6L Base/Cinco/RX-V as listed; 5-blade early waste-spark branch only. N…
- Genuine Kia 27301-26640 ignition coilOEMKia 27301-26640
Confirm the 2005 body transition and VIN.
- Genuine Kia 18823-11101 spark plugOEMKia 18823-11101
Replace worn or fouled spark plugs as a four-plug set on the later engine branch Fitment/availability: 2006-2011 Kia Rio/Rio5 1.6L Alpha DOHC; sold individually, order four. Confirm VIN and service-manual plug specification/gap.
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Owner tips & cautions
- TipUse dielectric grease sparingly in coil boots and inspect for oil in plug wells before installing new parts.
Find P0350 by make
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P0350 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0350 mean?
P0350 stands for "Ignition Coil Primary/Secondary Circuit Malfunction." This is a generic code indicating the engine computer detected a fault in an ignition coil's primary or secondary circuit. The computer monitors the coil control circuits that fire the spark plugs; when the expected electrical activity is missing or abnormal, this code sets. Because it does not always specify which coil, related cylinder-specific codes may also be present. It typically causes misfires, rough running, hesitation, hard starting, and reduced power.
What are the most common causes of P0350?
The most common causes of P0350 are: Faulty ignition coil or coil pack, Wiring or connector fault in the coil circuit, Open or shorted coil primary/secondary winding, Faulty spark plug or plug wire, Poor ground or power supply to the coil, Damaged PCM ignition driver circuit, Corrosion or moisture in coil connectors. The specific cause varies by vehicle.
How much does it cost to fix P0350?
Repair costs for P0350 range from $120 to $700, depending on the vehicle and root cause.
Which vehicles are affected by P0350?
Au7o has documented P0350 across 2 vehicle models from 2 manufacturers: Kia, Nissan.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.