Po340 & po341

2004 Saturn Ion 2.2 ecotec . Installed new spark plugs , coil pack & icm . Car seems to run fine but throws the PO341 code . Installed the original icm on the new coil pack & it throws the PO340 code . Seems to run fine either way . The 341 code is supposed to refer to the cam position sensor which this engine doesn’t have a typical one . It gets the signal from the icm when # 4 plug fires . The car suddenly started running very badly & the engine light came on with the PO340 code before I installed the new parts . The coil pack is all one piece so the coils can’t be swapped around & swapping the original spark plugs around made no difference in the way it ran or the PO340 code it was throwing . Any ideas ? TIA

There’s only two things that can cause those codes on your vehicle since the engine doesn’t have a camshaft position sensor.

Those are a bad ICM, which you’ve replaced, or a bad computer.


If it was running fine, why did you replace the plugs/coils/icm? Was that only because of a check engine and diagnostic code? If so, what codes were they? I mean the codes before you changed out those parts.

I’m not familiar with that engine, but if it doesn’t have a cam position signal to know where the camshaft is, how does it know that when the number four firing happens, it is on the intake stroke?

Read my post again .

That was a new one on me as well.

Apparently the crankshaft sensor is used to fire the spark plugs - two at a time. The ICM detects which plug is on the power stroke (vs exhaust stroke) by monitoring the secondary voltage on the plug coils. By looking at the difference in voltage, it can tell which cylinder is on the power stroke, and then sends a signal to the ECM (engine control module). The ECM then enables the fuel injector for that cylinder.

Interesting idea. There must be some kind of electrical difference in a cylinder on the compression stroke vs the exhaust stroke than can be observed by measuring the voltage at the coil secondary. Thanks for the explanation.

Thanks for editing for clarity. From what I gather, it started to run poorly and threw the p340 code, at which point you installed new parts, which fixed the poor running problem, but now you got a p341 code. both dtc’s refer to the camshaft position detector circuit, which on this car appears to be done by the icm by monitoring the spark plug secondary voltage of number 4. I’d guess you have one of these problems

  • the ecm needs to be reset to erase the code; i.e. it hasn’t cleared the code yet, but eventually may after a specific drive cycle sequence completes.

  • a problem with the new icm, its connecter, or its ground.

  • a problem with the number four coil, coil boot, spark plug wire connection (the one going from the icm to the coil), or spark plug. sp gap incorrect, cracks in sp ceramic, swap sp number 4 with another one, make sure coil is securely on the plug, boot doesn’t have cracks. any tendency of the number four spark to jump to ground at a point other than the sp electrodes could cause this. you might need to have a shop do an o’scope analysis of the number 4 ignition circuit. measure primary and secondary coil resistances, comparing number 4 to the other 3.

  • could have a problem with compression on number 4, or intake/exhaust valve or valve clearance problem

  • battery & charging system

I see in your list of replacement parts is no plug boots. A bad boot can cause both codes.

New boots came with the coil pack . The coil pack sits right on top of the plugs so there are no plug wires .

But there’s low voltage wires that go to the coil packs, right?

Just thought I’d update , new coil pack & or new ignition control module was defective . I ordered & installed oem parts & problem is gone .

Just out of curiosity . . .

what brand were the new parts that were defective?

The defective parts were aftermarket purchased from AIP Electronics . I should have known better . At least they’re giving me a full refund minus return shipping .

Glad to hear you’re getting all your money back for those defective parts, except for the shipping

One time I ordered some bad parts from rockauto

They readily agreed to refund my money, but they wanted me to ship the parts back to them

I persuaded them to just let me throw it in the trash . . . since it was of no use to anybody . . . and refund me all of my money, thus making it simpler for everybody

And I did wind up buying the genuine part from a dealer, and it worked out fine.

I am having the exact same issues with my 2004 saturn ion 2.2l ecotec. The ICM was bad, creating #2 & 3 to misfire, sending fuel down to the cat and roasting it. I changed the ICM the car running pretty smooth. Now a P0341 code pops up. As you know the 2.2l ecotecs do not have cam position sensors. After reading this thread I feel that the crankshaft position sensor is bad. Was that your issue? If not have you solved this problem?

I guess someone didn’t really read the comments, the problem was solved over 3 years ago.

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Hi @Chulachaser:
Welcome to this board. It is often difficult to see the dates on the older threads. Many do reply to old threads where the person who asked the question has moved on from the problem.

Given you’re having a problem, similar or not, if Sloepoke’s reply doesn’t help, then please do open a new post with all the info needed for us to help you solve it.

I did read the entire thread. I have also replaced to coil pack and icm. Which I STILL have a P0341 code. So that’s why I’m asking, after doing more research, if the crankshaft position sensor would have anything to do with it. As that’s what other forums have suggested.

That was what you asked and it was answered 3 years ago.

If you wanted to ask if there wee other problems, it sure wasn’t apparent.