P0350 Code: Ignition Coil Primary/Secondary Circuit Malfunction
The shared coil feed, ignition module or coil wiring is faulty. Often set with several P0351–P0358 codes.
At a glance
Severity: Moderate
- Meaning
- Ignition Coil Primary/Secondary Circuit Malfunction
- System
- Ignition & Misfire · Powertrain
- Safe to drive?
- With caution
- Typical repair cost
- $5–$1,500
- DIY difficulty
- Moderate
The engine computer switches each ignition coil's primary winding on and off, either directly through its own driver transistors or by commanding a separate ignition control module. While it does that it watches the primary circuit: the voltage on the trigger wire, how fast the current builds, and on many engines a confirmation pulse sent back from the coil. P0350 is the non-specific version of that check. The computer has seen a coil circuit fault but either cannot assign it to one coil, or the engine has a single coil or module serving every cylinder. That makes P0350 typical of three layouts: distributor engines with one coil, wasted-spark coil packs with a built-in module, and coil-on-plug engines where the 12-volt feed, ground or module shared by all coils has dropped out. The first thing to establish is whether cylinder-specific codes P0351 to P0358 are stored alongside it.
Can I keep driving? If the engine is running normally you can drive gently to a shop. A loose shared feed can open up without warning, and then the engine stalls or won't restart, so avoid situations like fast highway merges or railroad crossings where a stall would be dangerous.
How to read P0350
- P Powertrain
- 0 Generic (SAE)
- 3 Ignition / misfire
- 50 Specific fault
Symptoms
- Check-engine light, sometimes together with several coil circuit codes
- Engine cranks but won't start, or stalls and then restarts after a minute
- Intermittent cutting out over bumps or once the engine bay is hot
- Rough running on several cylinders at the same time
- Tachometer needle stays at zero while cranking on older distributor systems
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Chafed, melted or corroded shared coil power feed or ground, often at a harness splice
- Failed ignition control module, or a wasted-spark coil pack with the module built in
- Blown ignition coil fuse or a worn ignition relay with burned contacts
- The single coil on a distributor engine has failed or arcs internally
- Connector damage at the module or coil pack: bent pins, spread terminals or water inside
- A previous repair splice or aftermarket wiring tap coming loose
- Coil driver stage inside the engine computer has failed, usually after a shorted coil
Diagnosis step by step
Read every stored code before touching anything
P0350 rarely comes alone. Several P0351–P0358 codes at once point to a feed, ground or module shared by those coils. P0350 by itself points to a single-coil, distributor or coil-pack engine, or to a computer that cannot separate the coils electrically. Note the freeze-frame data too, because a fault that only appears hot or at idle narrows the search.
Tools: OBD-II scanner
Check the coil fuse and ignition relay
Find the fuse that feeds the coils in the underhood fuse box and test it with a meter rather than by eye, since a hairline crack can look intact. Then swap the ignition relay with an identical relay from a non-critical circuit such as the horn. If the problem moves, the relay was the cause.
Tools: Multimeter
Measure voltage at every coil connector
With the key on, one pin at each coil or at the coil pack should carry battery voltage. Then check the ground side during cranking: more than a few tenths of a volt of drop between the coil ground and the battery negative post means a corroded ground strap or eyelet. A missing feed at all coils means the fault is upstream, not in any coil.
Tools: Multimeter
Test for spark while cranking
Clip an inline spark tester to a plug lead or coil boot and crank the engine. No spark at any cylinder with a good feed confirms the module, single coil or trigger side is at fault. Spark that disappears once the engine is warm is classic behavior for a failing ignition control module.
Tools: Spark plug socket, Flashlight
Check the trigger signal at the module input
Back-probe the trigger wire from the engine computer with a logic-probe style LED test light or a scope while cranking. A pulsing signal reaching the module but no coil switching means the module is dead. No trigger at all means the fault is in the wire back to the computer or in the computer itself.
Tools: Multimeter, OBD-II scanner
Walk the harness at the usual chafe points
Follow the coil harness where it crosses the edge of the valve cover, passes near the exhaust manifold heat shield, and reaches the engine-to-body ground straps. Look for green corrosion inside splices and insulation that has gone hard or shiny from heat. Clean the ground eyelets to bare metal and reassemble with dielectric grease.
Tools: Flashlight, Screwdriver
Consider the engine computer last
If feed, ground, trigger wire and module all check out, the driver inside the computer may have failed. Before replacing it, measure every coil's primary resistance, because a shorted coil is the usual reason a driver burns out and it will take the new computer with it.
Tools: Multimeter
Where the parts are
- 1Ignition coil
- 2Spark plug
- 3Fuel injector
- 4Camshaft sensor
- 5Crankshaft sensor
- 6Engine computer (ECM)
- 7Intake manifold
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Replace coil fuse or ignition relay (after finding the cause) | Yes | $5–$60 |
| Repair shared coil feed, ground strap or harness splice | No | $100–$350 |
| Replace ignition control module | Yes | $120–$450 |
| Replace wasted-spark coil pack | Yes | $150–$450 |
| Replace and program engine computer | No | $600–$1,500 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Chevrolet
Older GM V6 engines with wasted-spark ignition (3.1L, 3.4L and the 3800) mount three coil packs on top of a separate ignition control module. When the module fails it usually kills spark on more than one cylinder pair and sets P0350 rather than a single coil code. The classic pattern is an engine that dies hot and restarts after cooling down.
Emissions / smog test impact
Will fail
A stored P0350 with the check-engine light on fails an OBD-II smog check outright. If the fault leaves the car unable to start or stalling, it cannot be tested at all, so fix the wiring or module first and drive a few days for the monitors to reset.
Frequently asked questions
What is the difference between P0350 and P0351?
P0351 through P0358 name a specific coil: A is cylinder 1, B is cylinder 2 and so on. P0350 is the general version the computer sets when the fault affects the shared part of the circuit, or when the engine has only one coil or module for all cylinders.
Can P0350 stop the car from starting?
Yes. If the shared feed, ignition relay or module has failed, no coil gets power and the engine cranks without firing. If only one coil in a pack has failed, the engine will start but run rough.
Does P0350 mean the engine computer is bad?
Rarely. Fuses, relays, corroded grounds and ignition modules fail far more often than the driver inside the computer. Only suspect the computer when the feed and trigger wiring have been proven good end to end.
I have P0350 and P0300 together. Which do I fix first?
The electrical code. P0300 is the random misfire that results when the coils lose power intermittently. Once the ignition circuit is repaired and the codes cleared, P0300 should not return on its own.