Ignition

P035C — Ignition Coil C Primary/Secondary Circuit Malfunction

Severity: medium Drive with care, to a shop

What P035C means

The engine control module fires each ignition coil through a driver circuit and monitors the current in the primary side. P035C sets when the signal in the circuit for coil "C" is not what the ECM expects, due to an open, short, poor connection or a failed coil. Which cylinder coil C serves depends on the manufacturer and engine, so check the vehicle-specific service information.

Symptoms

  • Check Engine light on or flashing
  • Misfire or rough idle
  • Loss of power and sluggish acceleration
  • Hesitation or jerking under load
  • Worse fuel economy
  • Hard starting

Possible causes

  1. Failed ignition coil C (most common)
  2. Damaged or corroded wiring to the coil
  3. Poor connection or corrosion at the coil connector
  4. Open circuit in the coil's power or ground
  5. Oil or moisture in the spark plug well causing coil breakdown
  6. Faulty coil driver inside the ECM (rare)

How to diagnose

  1. Scan all codes and freeze frame data, and look for related misfire codes (P030x)
  2. Find out which cylinder coil C serves using vehicle service information
  3. Inspect the coil connector and harness for heat damage, corrosion, chafing or broken wires
  4. Test power, ground and control signal at the coil connector with a multimeter or scope
  5. Swap coil C with a known good coil and see whether the fault or misfire follows
  6. Inspect the spark plug and plug well in that cylinder
  7. Measure coil winding resistance and compare it to the manufacturer's specification
  8. If coil and wiring are good, check the control circuit back to the ECM

Common fixes

  • Replace ignition coil C
  • Replace the spark plug in the same cylinder if worn
  • Repair the wiring or replace a damaged connector
  • Clean terminals and restore a good ground connection
  • Repair or replace the ECM if the driver fault is confirmed

Questions and answers

What does P035C mean?

It is a circuit fault for ignition coil C: the ECM sees an incorrect electrical signal in its primary or secondary circuit. The coil itself or its connector and wiring are the usual culprits.

Can I drive with a P035C code?

Only briefly and under light load. Ongoing misfires can damage the catalytic converter, and if the check engine light flashes you should stop driving.

Is replacing the coil enough to fix P035C?

Often, but check the connector, wiring and spark plug first. If the cause is a broken wire or bad contact, a new coil will not fix it or may fail soon.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.