After my second coil failed I ordered a set of Hitachi ones that were claimed to be oem parts, but the first one I installed sets the CEL with ignition circuit code.

Strangely, the Duralast coil that's in there hasn't set any codes.


Since the car runs fine now, does this code matter, at least before I need to smog again? I'm nervous because the last coil that failed was never detected and I possibly burned up the catalytic converter while continuing to drive it.

Isn't that ironic? Bum dead coil sets no CEL or code, but brand new Hitachi sets CEL instantly... Or is my computer messed up here?

 

Can you identify the coil causing the code or are you getting the generic P0300 or P1320?

You got a bad coil in the new set. New parts can fail. It happens. Get a replacement. Or maybe the condenser in the coils power supply circuit is bad (part # 28351-89901 Condenser-Ignition Coil).

Your computer is probably fine, although I have not seen a bad coil that did not cause a code. I've run 4 autozone coils spread between 3 cars and had no problems with them.

 

The code doesn't specify which coil but just general ignition circuit fault. I'm reading the codes from the CEL light flash pattern and get 2 long and 1 short.

So there is no additional misfire code like the last time a coil failed.

I looked at the bad coil more and there is no continuity between the spring connection to the spark plug and any of the three pins that connect to the harness. So it seems that the secondary is an open circuit. Maybe the computer can't detect this kind of failure because the electrical characteristics of the primary remain the same?

I think I will try marking every coil to keep track and then measuring the resistance of each primary and secondary and see how the new coils compare to the originals that still work fully and the Autozone one.

Really good to hear Autozone worked for you, I'll keep that in mind.

 

blinking light 02 01 is P1320. Did you have this code before you installed the Hitachi coils? P1320 is a nasty code that is usually resolved by replacing all the coils. If this code started after installing the Hitachi coils, I would see if you can get another set.

Other possible causes are:
Power transistor unit built into ignition coil
Condenser
Crankshaft position sensor (REF)
Crankshaft position sensor (REF) circuit
Harness or connectors (The ignition primary circuit is open or shorted.)

For some reason, you will not get a continuity reading for the secondary winding. In theory, a reading should be obtained between the pin 1 connection (12 volt supply) and the spark plug connector, but only in one direction as there is a diode between the secondary coil and the spark plug connection.

The car's ECU (computer) does not monitor the secondary winding. Basically it monitors the power transistor. Because the primary winding is connected to the power transistor, it gets monitored more or less like a piece of wire in the power transistor circuit.