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Discussion Starter #1
Hi all,

I'm nearly stuck on my search for the cause of a mystery misfire in cylinder 1 of my 2007 Saab 9-3 Aero 2.8L Manual... My BlueDriver code reader is spitting out P0201 and P0301, and after replacing the cylinder 1 coil and plug, all the injectors, and performing countless tests, I have established the following:

Cylinder 1 is not getting any gas, despite having a new injector (injector is NOT clicking, and plug comes out dry)
Cylinder 1 is not firing, despite having a new coil and sparkplug (I do not have the tool to verify presence of a spark, but this coil and plug worked in another cylinder)
Injector 1 is getting 12V through the wire when the key is in the "on" position. I will try to test the ground wire today.
Cylinder 1 coil is getting 12V through wire when the key is in the "on" position. The other three wires give the same readout as for the wiring to the working coils. I will try to test the signal frequency to cylinder 1 today with the car running.
Any idea where to turn next? In my way of thinking, it has to be either a wiring problem between the coils and/or injectors and the ECU, or the ECU itself...

Thanks so much for the help! I have tons more info I could share, so ask any questions you think would shed more light on the situation...
 

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Yes, ECU or wiring is bad. It's unusual that both injector and coil drive for one cylinder would fail in ECU. Wiring seems more likely.
 

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Discussion Starter #3
Thanks! That sounds likely. The only reason I would wonder otherwise is that another website (not Saab specific) said the ECU might shut down an injector if it senses a misfire in that cylinder... not sure if this would throw an injector code though.

I'll see what I can do with the wiring today...
 

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Discussion Starter #4
It occurs to me that it would be very helpful to know whether the coil/plug in cylinder 1 is actually sparking (duh... not sure why I didn't realize this earlier). I'll buy an inline tester later this morning and check it out. If I'm getting a spark there, the problem must be the wiring to the injector or the ECU not signaling the injector properly.
 

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ECU would cut off an injector only as last resort to continuous misfires, if that's what you're getting.
 

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Discussion Starter #6
Checked the spark today both at cylinder 1 and a few other good cylinders - all are sparking perfectly fine! Sooo… it's got to be some problem with the wiring to the injector, or the ECU, unless I'm missing something
 

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Nope. Just don't forget to check connectors since they are also part of wiring.
 
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