What does it mean?
This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to vehicles equipped with OBD-II. Although generic, specific repair steps may vary by brand/model.
The COP (coil-on-plug) ignition system is what is used on most modern engines. There is an individual coil for each cylinder that is 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 usually from the electrical 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 the #7 coil control circuit, a P0357 may set. Additionally, depending on the vehicle, the PCM may also shut off the fuel injector for that cylinder as well.
Symptoms
Symptoms of a P0357 DTC may include:
- MIL (malfunction indicator lamp) illumination
- Engine misfire may be present or intermittent
Causes
Potential causes of a P0357 code include:
- Short circuit to voltage or ground on the COP driver circuit
- Open in the COP driver circuit
- Loose connection at the coil or broken connector locks
- Faulty coil (COP)
- Defective powertrain control module
Possible Solutions
Is the engine currently misfiring? If not, the problem is likely intermittent. Try testing the wiring at coil #7 and along the wiring harness to the PCM. If manipulating the wiring causes a misfire to surface, repair the wiring issue. Check for poor connection at the coil connector. Verify the harness is not improperly routed or rubbing against anything. Repair as necessary.
If the engine is currently running poorly, stop the engine and disconnect the wiring connector from coil #7. Then start the engine and look for a driver signal at coil #7. Using an oscilloscope will give you a visual pattern to observe, but since most people don’t have access to one, there is a simpler way. Use a voltmeter set to the AC Hertz scale and see if there is a Hz reading between 5 and 20, indicating the driver is operating. If there is a Hertz signal, replace ignition coil #7. It is likely faulty. If you detect no frequency signal from the PCM on the ignition coil control circuit, indicating the PCM is not grounding/ungrounding the circuit (or if there is no visible pattern on the oscilloscope if you have one), leave the coil disconnected and check for DC voltage on the control circuit at the ignition coil connector. If there is significant voltage on this wire, there is a short somewhere. Find the short and repair it.
If there is no voltage on the control circuit, turn the ignition off. Disconnect the PCM connector and check the continuity of the driver circuit between the PCM and the coil. If there is no continuity, repair the open circuit or short to ground in the circuit. If continuity is present, check the resistance between ground and the ignition coil connector. There should be infinite resistance. If there isn’t, repair the short to ground in the coil control circuit.
NOTE: If the ignition coil driver signal wire is not open or shorted to voltage or ground and there is no trigger signal to the coil, suspect a faulty PCM coil driver. Also keep in mind that if the PCM driver has failed, there may have been a wiring issue that caused the PCM failure. It is a good idea to perform the above check after PCM replacement to verify there will be no repeat failure. If you find the engine is not misfiring, the coil is being triggered correctly but the P0357 is continuously reset, there is the possibility that the PCM coil monitoring system is faulty.