P0350
Ignition Coil Primary/Secondary Circuit MalfunctionP0350 is a generic OBD-II powertrain diagnostic trouble code: Ignition Coil Primary/Secondary Circuit Malfunction. It is logged by the engine control unit when the ckp/cmp monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0350 means
P0350 is a generic OBD-II code meaning the PCM has detected a fault in the ignition coil primary and/or secondary circuit, but cannot identify which specific cylinder or coil is affected. It is the non-specific parent code in the P0350–P0362 family; codes P0351 through P0362 each correspond to a specific ignition coil ("A" through "L", mapping to cylinders 1 through 12). P0350 is set when the system detects a coil circuit problem but the PCM either cannot distinguish which coil is faulty, or the fault affects a component common to multiple coils.
The ignition coil operates as a step-up transformer. The primary circuit is the low-voltage side: the PCM grounds the primary winding to build a magnetic field. The secondary circuit is the high-voltage output side: when the PCM breaks the primary current, the collapsing magnetic field induces thousands of volts in the secondary winding, firing the spark plug. A fault in either winding, or in the shared power supply or ground circuit that feeds multiple coils, can trigger P0350.
P0350 is particularly associated with older coil-pack (waste-spark) ignition systems where a single coil fires two cylinders simultaneously, and with any architecture where the PCM shares a common ignition power feed or control ground across coils without per-coil identification. In modern coil-on-plug (COP) systems the PCM can usually identify the failing coil individually, producing P0351–P0362 instead. P0350 on a modern COP system may suggest a supply-rail or PCM driver fault rather than a single bad coil.
Common causes
Most-frequently reported root causes when P0350 is logged.
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1
Defective ignition coil or coil pack with an open or shorted primary winding (typical resistance 0.4–2 Ω) or secondary winding (typical resistance 6,000–15,000 Ω)
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2
Open or shorted wiring in the ignition coil primary circuit (power feed wire from ignition relay, or PCM control/ground wire)
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3
Corroded or damaged ignition coil electrical connector causing high-resistance contact
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4
Faulty ignition relay or blown fuse/fusible link interrupting the shared coil power supply
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5
Failed ignition control module (ICM) on distributor-based or coil-pack systems where the ICM drives coil primary switching
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6
PCM internal driver fault on the ignition coil control output — on coil-pack systems a single PCM driver controls multiple coils, so a failed driver sets P0350 rather than a cylinder-specific code
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7
Damaged secondary high-tension lead or spark plug boot causing secondary circuit breakdown
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8
Aftermarket or modified ignition components with incompatible resistance or firing characteristics
Symptoms drivers notice
How to diagnose P0350
A typical diagnostic flow when this code is present.
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1
Retrieve all stored DTCs — the presence of cylinder-specific misfire codes (P0301–P0308) alongside P0350 narrows the faulty coil; if only P0300 or P0350 appear, suspect a supply-rail or PCM driver fault
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2
Perform a visual inspection of all coil packs, connectors, spark plug boots, and ignition wiring for cracks, burn marks, arcing carbon tracks, corrosion, or melted insulation
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3
Check the ignition system fuse and relay; a blown fuse feeding the coil supply rail kills all coils on that circuit simultaneously and produces P0350 without a cylinder-specific companion code
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4
Use a DVOM to verify battery voltage (~12 V with ignition on) is present at the coil pack power connector; absence points to the relay, fuse, or feed wiring
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5
Measure primary winding resistance across each coil with the connector disconnected (typically 0.4–2 Ω); out-of-spec readings indicate a failed coil
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6
Measure secondary winding resistance across the coil high-tension terminals (typically 6,000–15,000 Ω); infinite resistance (open winding) indicates secondary failure
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7
On coil-on-plug systems, perform a coil swap test: move the suspect coil to another cylinder and check whether the misfire follows the coil or stays on the original cylinder — if it follows the coil, the coil is faulty; if it stays, investigate the PCM control wire or injector circuit for that cylinder
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8
Check for relevant Technical Service Bulletins (TSBs) — P0350 on certain platforms is associated with known ignition coil batch failures or PCM firmware issues requiring software updates
Related powertrain codes
- P000A — A Camshaft Position Slow Response Bank 1
- P000B — B Camshaft Position Slow Response Bank 1
- P000C — A Camshaft Position Slow Response Bank 2
- P000D — B Camshaft Position Slow Response Bank 2
- P0010 — A Camshaft Position Actuator Circuit (Bank 1)
- P0011 — A Camshaft Position - Timing Over-Advanced or System Performance (Bank 1)
Frequently asked questions
What is the difference between P0350 and P0351–P0358?
P0351 through P0358 (or P0362 on 12-cylinder engines) each identify a specific ignition coil by cylinder assignment: P0351 = Coil A (typically cylinder 1), P0352 = Coil B (cylinder 2), and so on. P0350 is set when the PCM detects a coil-circuit fault but cannot pinpoint a single coil — either because the fault is in a shared supply/ground, or because the system architecture does not support individual coil identification.
Why does P0350 appear on coil-pack (waste-spark) engines?
Coil-pack systems fire pairs of cylinders from one coil (e.g., cylinders 1 and 4 share a coil). If that coil fails, both cylinders misfire but the PCM may log P0350 rather than two cylinder-specific codes, because the system only monitors the coil as a unit rather than mapping it to individual cylinders.
Can a bad spark plug cause P0350?
Indirectly. A fouled or cracked spark plug creates abnormal secondary circuit load that can overload and eventually fail the coil. However, a single bad plug on a COP system typically produces a cylinder-specific P035x code rather than the generic P0350. If P0350 appears with no cylinder-specific codes, focus on the coil supply circuit and PCM driver before the plugs.
How urgent is P0350 to repair?
Urgent. Persistent misfire caused by a coil fault sends unburned fuel into the exhaust, which can overheat and damage the catalytic converter within minutes of sustained misfiring. Drive only as far as needed to reach a repair facility, and avoid sustained high-load operation.
What are the primary and secondary coil resistance specifications?
Primary winding resistance is typically 0.4–2 Ω (low-voltage side). Secondary winding resistance is typically 6,000–15,000 Ω (high-voltage output side). Exact values vary by manufacturer — consult a vehicle-specific service manual. Readings of 0 Ω (short) or infinite Ω (open) in either winding confirm a failed coil.
Disabling P0350 in software
RaceTune can permanently disable P0350 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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