What does it mean?
This diagnostic code (DTC) is a generic powertrain code, meaning it applies to vehicles equipped with OBD-II. Although generic, specific repair steps may vary by make/model.
The COP (coil-on-plug) ignition system is what’s used on most modern engines. There’s an individual coil for each cylinder that’s controlled by the PCM (powertrain control module).
It eliminates the need for spark plug wires by placing the coil right above the spark plug. Two wires are dedicated to each coil. One is a battery supply typically from the power distribution center. The other wire is the coil control circuit from the PCM. The PCM grounds/ungrounds this circuit to activate or deactivate the coil. The coil control circuit is monitored by the PCM for faults.
If an open or short circuit is detected in coil #6 control circuit, a P0356 may set. Additionally, depending on the vehicle, the PCM may also shut off the cylinder’s fuel injector as well.
Symptoms
Symptoms of a P0356 DTC may include:
MIL (malfunction indicator lamp) illumination
Engine misfire may be present or intermittent
Causes
Potential causes of a P0356 code include:
Short to voltage or ground on COP driver circuit
Open in COP driver circuit
Loose connection at coil or broken connector locks
Bad coil (COP)
Faulty powertrain control module
Possible Solutions
Is the engine currently misfiring? If not, the problem is likely intermittent. Try testing the wiring at coil #6 and along the wiring harness to the PCM. If manipulating the wiring causes a surface misfire, repair the wiring issue. Check for poor connection at coil connector. Check that harness isn’t misrouted or chafing against anything. Repair if necessary.
If engine is currently running rough, stop engine and disconnect wiring connector from coil #6. Then start engine and check for driver signal at coil #6. Using a scope will give you a visual pattern to observe, but since most people don’t have access to one, there’s a simpler way. Use a voltmeter on AC Hertz scale and see if there’s a Hz reading between 5-20, indicating the driver is working. If there’s a Hertz signal, replace ignition coil #6. It’s probably bad. If you detect no frequency signal from PCM on ignition coil control circuit, indicating PCM isn’t grounding/ungrounding the circuit (or if there’s no visible pattern on oscilloscope if you have one), leave coil disconnected and check DC voltage on trigger circuit at ignition coil connector. If there’s significant voltage on this wire, there’s a short somewhere. Find the short and repair it.
If there’s no voltage on trigger circuit, turn ignition off. Disconnect PCM connector and check continuity of driver between PCM and coil. If there’s no continuity, repair open circuit or short to ground in circuit. If continuity is present, check resistance between ground and ignition coil connector. There should be infinite resistance. If there isn’t, repair short to ground in coil control circuit.
NOTE: If ignition coil driver signal wire isn’t open or shorted to voltage or ground and there’s no trigger signal to coil, suspect faulty PCM coil driver. Also keep in mind that if PCM driver has failed, there may have been a wiring problem that caused PCM failure. It’s a good idea to perform above check after PCM replacement to verify there won’t be repeat failure. If you find engine isn’t misfiring, coil is triggering properly but P0356 keeps resetting, it’s possible PCM coil monitoring system is faulty.