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Severity: Moderate Code type: Manufacturer-specific (Nissan)

Nissan P1320 Code: Ignition Signal – Primary Circuit (Nissan)

The Nissan ECM isn't seeing the ignition primary signal it expects while the engine cranks or runs.

At a glance

Severity: 3/5 – Moderate3/5

Severity: Moderate

Meaning
Ignition Signal – Primary Circuit (Nissan)
System
Ignition & Misfire · Powertrain
Safe to drive?
With caution
Typical repair cost
$0–$900
DIY difficulty
Moderate

Most Nissan gasoline engines of the QG, QR and VQ generations use a coil-on-plug design in which every ignition coil has its own power transistor built in. The ECM sends a low-current trigger to each coil, the power transistor switches the coil's primary winding, and the ECM watches the primary side to confirm that the ignition events actually happened. P1320 sets when that primary ignition signal goes missing during cranking or running. Unlike the generic coil codes, it does not always tell you which cylinder, so the diagnosis is about finding the one coil, feed wire or ground that is dragging the whole circuit down. The coil power supply on these engines also carries a small condenser (a suppression capacitor), which is a Nissan-specific suspect when it shorts.

Can I keep driving? Drive gently and only as far as needed. If a misfire comes with it, especially with a flashing check engine light, stop driving hard, because raw fuel can overheat the catalytic converter.

How to read P1320

How to read P1320P11233204
  1. P Powertrain
  2. 1 Manufacturer-specific
  3. 3 Ignition / misfire
  4. 20 Specific fault

Symptoms

  • Check engine light, sometimes flashing under load
  • Misfire or stumble on acceleration, often felt at 2,000–3,500 rpm
  • Rough idle that smooths out when you rev the engine
  • Stalling or a long crank before it starts
  • Misfire codes P0300–P0306 stored alongside

Possible causes

Ranked by how often each cause is behind this code (editorial estimate).

  1. One ignition coil with a failing built-in power transistor loading the circuit 42%
  2. Loose, corroded or oil-soaked coil connector, or chafed trigger wire 16%
  3. Shorted or leaking condenser on the coil power supply 12%
  4. Worn or wrongly gapped spark plugs overstressing the coils 12%
  5. Weak coil power feed: ECM or ignition relay, fuse or ground point 10%
  6. Crankshaft position sensor dropping out 5%
  7. ECM ignition driver fault 3%

Diagnosis step by step

Diagnostic flow: P13201Read misfire counters2Unplug coils one at a time3Spark test and swap test4Check the coil feed and condenser5Look at plugs and grounds6Crank sensor and ECM last

  1. Read misfire counters

    Check for P030x codes and live misfire counts per cylinder. A cylinder that racks up misfires points straight at its coil. Also note whether the fault appeared hot or cold in freeze frame, since failing coils often act up when heat-soaked.

    Tools: OBD-II scanner

  2. Unplug coils one at a time

    With the engine idling, unplug each coil connector briefly and note the rpm drop. A cylinder that makes no difference is already dead. On transverse V6 models the rear coils sit under the intake plenum, so the plenum usually comes off to reach them.

    Tools: Screwdriver

  3. Spark test and swap test

    Test spark from the suspect coil with an adjustable spark tester; a healthy Nissan coil fires reliably across a gap of roughly half an inch. Swap the suspect coil with a neighbor and see whether the misfire follows it.

    Tools: Spark plug socket

  4. Check the coil feed and condenser

    With the key on, each coil connector should have battery voltage on the feed wire. Unplug the condenser and check it with an ohmmeter: it should read very high resistance (above about 1 megaohm); a low reading means it is shorting the feed.

    Tools: Multimeter

  5. Look at plugs and grounds

    Pull the plugs and check the gap and wear; iridium plugs on these engines are long-life but not lifetime. Clean and tighten the engine ground straps and the coil harness ground, because a poor ground distorts the primary signal the ECM watches.

    Tools: Spark plug socket, Torque wrench

  6. Crank sensor and ECM last

    If all coils and feeds are good, graph the crank sensor signal for dropouts. Only when the trigger wires check out from ECM to coil should the ECM be considered.

    Tools: OBD-II scanner, Multimeter

Where the parts are

Ignition: coils and spark plugs per cylinder – P13201234567
Ignition: coils and spark plugs per cylinder
  1. 1Ignition coil
  2. 2Spark plug
  3. 3Fuel injector
  4. 4Camshaft sensor
  5. 5Crankshaft sensor
  6. 6Engine computer (ECM)
  7. 7Intake manifold

Repair options & costs

RepairDIY?Estimated cost
Clean or repair coil connector or ground Yes $0–$150
Replace condenser on coil supply Yes $40–$150
Replace one ignition coil (front bank or four-cylinder) Yes $110–$280
Replace rear-bank coils on a V6 including plenum removal No $350–$900
Replace spark plugs set Yes $120–$450

Rough US estimates for parts and labor; shop rates vary by region. Not a quote.

Emissions / smog test impact

Will fail

P1320 lights the check engine light and usually comes with misfire codes, so the car fails an OBD-based smog or emissions inspection until it is repaired and the monitors have run again.

Frequently asked questions

Does P1320 tell me which coil is bad?

Not directly. The ECM sees the shared primary signal go missing. Use misfire counters, the unplug test and a swap test to find the coil or wire at fault.

Should I replace all the coils at once?

On high-mileage engines where one coil has failed and others are original, many owners replace the full set to avoid repeat visits, especially on a V6 where the rear bank needs the plenum removed. It's not required if the others test fine.

What is the condenser on a Nissan ignition system?

It's a small capacitor on the coil power feed that suppresses electrical noise. If it shorts internally it can drag down the coil supply and trigger P1320, so it's a cheap part worth checking.

Sources