Q: Secondary coil replacement for a 2007 ES 350 Lexus

Hi there. That code is set when the primary or secondary circuit for the specified coil has failed. If you are not experiencing any drivability concerns, then it is most likely that the circuit has not failed to the point of misfiring. The code stored, P0352, specifies ignition coil B also known as cylinder #2 ignition coil. This coil is located on the left hand bank, towards the front of the vehicle, and is the first coil towards the passenger side.

Check the connector for looseness or broken wires and correct as necessary. Mark the top of the coil and swap it with another cylinder and recheck for codes to see if the code changes to the new cylinder. If it does change, then the coil is faulty. If it does not change, then swap the spark plug and repeat.

If no change is determined after swapping the plug and coil, then the wire harness or ECU may be at fault. These can be tested with a digital volt/ohm meter, scan tool that provides data, and the electrical wiring diagram. Check for an open/short circuit in the harness from the coil to the ECU and correct as necessary. If the harness is ok, or a repair is completed and the code returns after clearing, suspect the ECU.

I strongly suggest having a qualified technician perform an inspection to avoid replacing unnecessary parts. YourMechanic has several technicians available that can assist you with a Check Engine Light inspection and make the necessary changes.