P0359Generic code

P0359 Code: Ignition Coil I Primary/Secondary Circuit

The P0359 code means the computer found a fault in the circuit of ignition coil I, which normally belongs to cylinder 9. It is usually accompanied by a misfire in that cylinder. A cylinder with no spark can overheat the catalytic converter, so do not put off the repair.

Severity
High
Can I keep driving?
Yes, but with caution
Estimated cost
$30 to $300
Difficulty
Easy
System
Ignition and Misfires
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0359 code means

The computer, or an ignition module, charges each coil by connecting its primary winding to ground. When the current is cut, the coil generates the high voltage that jumps across the spark plug gap. Many computers watch the primary current or voltage and detect when a coil is not charging or not responding.

The letter I identifies the coil: A is cylinder 1, B is cylinder 2, and so on, although some manufacturers follow the firing order. The manufacturer sets the cylinder numbering. On most inline engines cylinder 1 is the one closest to the timing belt or chain end. On V engines the odd and even cylinders are usually on different banks. Confirm it in the manual before you take anything apart. A cylinder 9 coil only exists on engines with at least nine cylinders, which means V10 or V12 engines.

There are two common designs. In a coil-on-plug (COP) system each cylinder has its own coil and a fault affects just one cylinder. In a wasted spark system one dual coil feeds two cylinders at once (for example 1 and 4, or 2 and 3 on a four-cylinder engine), and if it fails you will see misfires on that pair.

The primary circuit is the low-voltage side (12 V and the command from the computer), and it is the one the computer can monitor. The secondary is the high-voltage side that goes to the spark plug. A crack in the boot, moisture in the spark plug well or a badly worn plug forces the coil to produce more voltage and ends up damaging it. That is why, when you replace a coil, you should also check its spark plug and boot.

A coil that does not work leaves its cylinder without spark. The unburned fuel reaches the catalytic converter and overheats it, so repair the P0359 code soon.

P0359 code symptoms

  • Check engine light on, often flashing.
  • Engine shaking.
  • Loss of power.
  • Misfire in the cylinder of that coil.
  • Fuel smell from the exhaust.

Likely causes of the P0359 code

  1. Failed coil I, with the primary winding open or shorted.
  2. Coil connector loose or corroded. Very common.
  3. Damaged control wire between the coil and the computer.
  4. No 12 V supply at that coil connector.
  5. Computer driver. Uncommon. It gets damaged if the coil was shorted.

How to diagnose the P0359 code step by step

  1. Confirm the affected cylinder with the misfire counters.
  2. Swap the coil with the one from another cylinder. If the code changes letter, the coil is the culprit.
  3. Check for 12 V at the connector with the key on.
  4. Measure the primary resistance if the design allows it (approximate: 0.4 to 1.5 ohms).
  5. Check the command signal with an LED test light or an oscilloscope while cranking.
  6. Inspect the boot and the spark plug. Carbon tracking or cracks point to high-voltage leaks.

How to fix the P0359 code

  • Repair the connector or the wiring.
  • Replace the faulty coil, and the spark plug as well if it is worn.
  • Repair the shared power supply if the code is the general one.
  • Clear the codes and verify that there are no more misfires.

Technical reference data

  • Individual coil (COP): 12 V supply and a command from the computer.
  • Approximate primary resistance: 0.4 to 1.5 ohms.
  • Secondary voltage: 20,000 to 40,000 V.
  • These are approximate values. Check the manufacturer data for your engine.

Brand-specific notes

Water collecting in the spark plug wells is a known cause of high-voltage leaks on coil-on-plug engines. If you find water or oil in the wells, fix the source before you replace any coils.

P0359 on Ford

On many Ford engines with coil-on-plug ignition, water collected in the spark plug wells causes high-voltage leaks. Check the valve cover gaskets.

P0359 on Chrysler

On many Chrysler engines with coil-on-plug ignition, water collected in the spark plug wells causes high-voltage leaks. Check the valve cover gaskets.

P0359 on Toyota

On many Toyota engines with coil-on-plug ignition, water collected in the spark plug wells causes high-voltage leaks. Check the valve cover gaskets.

Frequently asked questions about P0359

Can I drive with a P0359 code?
With caution and only for a short time. A cylinder without spark can damage the catalytic converter.
Which letter goes with which cylinder?
Normally A is cylinder 1, B is cylinder 2, and so on, so I is usually cylinder 9. Some manufacturers follow the firing order, so check the manual.
Should I replace all the coils?
It is not necessary if only one fails. If the coils have high mileage and the misfires keep repeating, replacing them all can make sense.
How much does it cost to fix P0359?
Roughly $30 to $300, depending on whether it is a connector, wiring or a coil with new spark plugs.
What does the P0359 code mean?
It is a generic OBD2 code that means there is a malfunction in the primary or secondary circuit of ignition coil I, normally the cylinder 9 coil.
Will a P0359 code clear itself?
A P0359 code may clear itself, because the light may go out if the fault was momentary, but a loose connector or a failing coil will bring it back. Do not wait on it, because a dead cylinder can overheat the catalytic converter.
What is the most common cause of P0359?
A failed coil or a loose, corroded connector at that coil. A swap test with another cylinder tells you which one it is.

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