P0356: Ignition Coil F Primary Control Circuit/Open

What does P0356 mean?

P0356 monitors the primary control circuit of ignition coil F – the line from the engine module to the coil or to its built-in output stage – for an open circuit or high resistance. Coil F usually serves cylinder 6, so the code only occurs on engines with at least 6 cylinders. GM's 6.2-litre V8s (LT4, LT5) flag an open circuit above 30 kΩ with the driver off in 50 of 63 samples, after two trips. Ford checks continuously from 200 rpm within 1 s, expecting a primary-current feedback for every ignition command, and then shuts off injection to that cylinder for 30 s at a time to protect the catalyst. GM bulletin PIP5038B describes coils on the 3.6-litre V6 (LLT) overheating from a permanently switched-on control signal; PIP5147 advises checking coil connectors for water. Short circuits have their own codes (P2315 ff).

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine light on
• Misfire and rough running on cylinder 6, often also P0306
• Loss of power, jerking under load
• Cylinder shut off (injection off), risk to the catalyst if driven on

Common causes

• High Ignition coil F faulty (output stage in the coil or primary winding open)
• High Connector at the coil corroded, wet or with a loose pin
• Medium Control, supply or ground wire open or chafed
• Low Driver in the engine module faulty or software (permanent dwell)

Likelihood is a general estimate across vehicles; your make and model may differ.