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P0359 – Ignition Coil I Primary/Secondary Circuit Malfunction (OBD2)

P0359 means "Ignition Coil I Primary/Secondary Circuit Malfunction". The control unit has detected a fault in the electrical circuit of the ignition coil: the signal or control current is missing or outside the expected window. The code does not say whether the value is too high or too low, so the wiring and the component itself both have to be checked.

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P0359 quick summary

Fault codeP0359
MeaningIgnition Coil I Primary/Secondary Circuit Malfunction
SystemPowertrain (Engine & Transmission)
VehiclesGeneric OBD2
SeverityHigh
Can I drive?Only gently. A dead coil means one cylinder is not firing, which causes misfires and can overheat the catalytic converter. Fix it as soon as possible.
Repair cost€20 – €300

How the ignition coil circuit is monitored

The ignition coil turns the 12 V supply into the very high voltage needed for the spark; these codes mean the control unit has detected a fault in a coil's primary or secondary circuit.

Most modern petrol engines have one coil per cylinder (coil-on-plug). The engine control unit switches the primary side of each coil on and off; when the current is interrupted, the coil produces tens of thousands of volts on the secondary side to fire the spark plug.

The control unit monitors the primary circuit – and on some engines feedback from the secondary side. If a coil draws no current, too much current, or the expected feedback is missing, it stores a coil code. Coil A usually corresponds to cylinder 1, B to cylinder 2 and so on, but the order can differ between manufacturers.

A coil circuit fault normally causes a misfire on that cylinder as well. Common causes are a failed coil, a damaged connector, a broken wire or a problem with the shared coil supply fuse or relay.

Ignition coil I is the 9. coil in the control unit's internal order. On most engines coil A belongs to cylinder 1, B to cylinder 2 and so on – but confirm it with the wiring diagram.

On VAG vehicles (VW, Audi, Škoda, Seat, Cupra), VCDS and older VAG testers can show this code as the five-digit VAG code 16743 (P0359). Both numbers mean the same fault.

Symptoms of P0359

  • Check Engine light, often flashing
  • Misfire codes for the same cylinder
  • Engine shakes, especially under load
  • Loss of power
  • Fuel smell from the exhaust

Most common causes of P0359 (most likely first)

Mechanic's Pro Tip

Oil in the spark plug wells is a coil killer. If you find oil when removing a coil, replace the valve cover or spark plug well seals at the same time – otherwise the new coil will fail again.

  1. 1.Damaged wire or loose, corroded connector at the ignition coil

    Most likely

    Green or white corrosion, pushed-back pins and chafed insulation near hot or moving parts are the most common findings.

  2. 2.Faulty ignition coil

    An internal break or short in the component itself.

  3. 3.Blown fuse or missing supply voltage

    If several codes appeared at the same time, check the shared fuse, relay or ground point first.

  4. 4.Worn spark plug with a large gap

    A plug that needs very high voltage overloads the coil and can damage it.

  5. 5.Fault in the control unit's coil driver

    Rare; sometimes caused by a shorted coil.

Step-by-step diagnostic guide

  1. 1

    Read codes

    Read all codes and note which coil and cylinder are affected. Several coil codes at once point to the shared supply, ground or fuse.

  2. 2

    Check the circuit with a multimeter

    With the ignition off, unplug the ignition coil and the control unit connector (or back-probe), then check each wire between them for continuity and for shorts to ground and to battery voltage. Compare the component's resistance or supply voltage with the value in the repair manual.

    Multimeter: Wire continuity: below about 1 Ω. Wire to ground with both connectors unplugged: no continuity. Supply/reference with ignition on: usually 5 V for sensors, battery voltage for actuators.

  3. 3

    Inspect the coil and spark plug well

    Remove the coil and look for cracks, burn marks and oil in the spark plug well. Check the spark plug condition and gap.

  4. 4

    Swap the coil

    Swap the coil with another cylinder and clear the codes. If the code follows the coil, replace it.

  5. 5

    Check supply and control wires

    With the ignition on, check the coil supply voltage and the ground. Check the control wire to the engine control unit for continuity and shorts.

    Multimeter: Supply: battery voltage with the ignition on. Primary resistance on coils with two-pin primary access: typically below about 1 Ω (many modern coils have built-in electronics and cannot be measured this way).

  6. 6

    Replace and clear

    Replace the faulty coil (and worn plugs), fix any oil leak into the plug wells, then clear the codes and confirm no misfires.

Frequently asked questions

Can I keep driving with P0359?

Only gently. A dead coil means one cylinder is not firing, which causes misfires and can overheat the catalytic converter. Fix it as soon as possible.

How much does it cost to fix P0359?

Typical repair costs are 20 € – 300 €, depending on the cause and the vehicle. The most common fixes are: damaged wire or loose, corroded connector at the ignition coil; faulty ignition coil; blown fuse or missing supply voltage. Always confirm the cause with the tests above before buying parts.

Which ignition coil is coil A?

On most engines coil A is cylinder 1, coil B cylinder 2 and so on. Some manufacturers use a different order, so check the wiring diagram or swap test before buying parts.

Should I use original or aftermarket coils?

OE-supplier coils (for example from Bosch, Beru, NGK or Delphi) are a safe choice. Very cheap unbranded coils often fail quickly or cause new misfires.

What is the difference between P0359 and similar codes?

P0359 belongs to a group of codes for the same component that differ in the type or location of the fault: P0356 – Ignition Coil F Primary/Secondary Circuit Malfunction; P0357 – Ignition Coil G Primary/Secondary Circuit Malfunction; P0358 – Ignition Coil H Primary/Secondary Circuit Malfunction; P0360 – Ignition Coil J Primary/Secondary Circuit Malfunction; P0361 – Ignition Coil K Primary/Secondary Circuit Malfunction; P0362 – Ignition Coil L Primary/Secondary Circuit Malfunction. The tests on this page apply to the whole group; the type of fault tells you where to start.

Related fault codes

This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.