P0351 P0352 P0353 P0354

How many miles since last tuneup? How low is the oil level... Before suspecting the coils, know that when you're way under a quart of oil the engine misfire warning lights get triggered from crankshaft bearing vibration... Also replacing spark plugs, cleaning MAF sensor and throttle body and air filter is prudent before you start switching around ignition coils to determine if that's the problem.

 

Those particular DTCs aren't triggered by vibration though. The ECM sends individual electrical signals to the four coils, telling each one when to fire. Each coil has an "IGF" (IGnition conFirmation) signal it sends back to the ECM when it has fired to confirm that it did.

The IGF signals from all four coils are commoned together and just make a single input to the ECM. So every time the ECM sends a "fire" signal on IGT1, IGT2, IGT3, or IGT4, it expects to see a pulse come back on IGF. (It can't strictly tell which coil sent the IGF pulse back, but all the betting is on the one that was just told to fire.)

The P035{1,2,3,4} codes mean the ECM electrically is not seeing that IGF signal when it tells the corresponding coil to fire. If there are all four codes, probably something is up with that common IGF wiring or that input to the ECM.

Someone did upload (most of?) the workup section for those codes, here.

Those are zeros in the second position of each code, by the way, not the letter O. That can help you get better hits when you search. To keep things easy, the first position of a DTC is always a P, C, B, or U. The second position is always a zero, one, two, or three. The remaining positions can be digits 0 through 9 or letters A through F.

 

ChapmanF covered most of it, and the link covers the rest. The ecm creates a 5 volt signal on pin 23 of connector E4 (that's the top connector when you pull the glovebox in the car). That one circuit is connected in parallel to each coil at pin 2 - it is the smaller of the two black wires.

Each coil very briefly (about 1-2 milliseconds) pulls that 5V down to about 0.75V to confirm that it has fired its plug. Since the engine only fires one coil at a time, the signal should be a steady repeating pattern of 5V with regular dips to 0.75V. This is a digital squarewave signal, and the best way to view it is with an oscilloscope.

Since you have tried different coils as well as a different ecm, that really only leaves the wiring on the car as the source of your problem. What you can try is to disconnect a coil and then turn the ignition ON but not READY. Use a multimeter to check the voltage at pin 2. You can use a T-pin to reach the connector terminal by either: "back probing" from the wire side if you know how, or using the tip of the pin to touch the metal end of the terminal. DO NOT jam anything into the terminal on the connector or you will damage it.

With the ignition on but engine off you should read 5V. If it higher than that then the circuit is shorted to power somewhere. If it is lower then it is shorted to ground or open circuit. Next check at the top ecm connector, the black wire at pin 23 is near the center. Looking at the wires going into the back of the connectors while they are still plugged in, you'll see the metal of the terminals. Again, use a large pin & you slide it into the cavity to touch the terminal for pin 23 & get a voltage reading there with ignition on.

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