My 07 Scion tC Is Not Firing At #4 Cylinder
I've Done Every Test I Know Changed Coil, Changed Spark Plug, Moved Coil To Different Cylinders,
Still Get Code PO354, On Everything I’ve Done. Bad PCM Is All I’m Left With.

Any Help Would Be Appreciated Thanks


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Do you have service-manual? Buy one, it's worth its weight in gold and would've more than saved you its cost from time-savings alone in this case.

Don't replace perfectly-working parts with brand-new perfectly working parts, nothing will change and symptoms will persist.

TEST and measure parts to arrive at NUMBERS. Then compare these numbers to standards in manual to determine if a part is good or bad. When numbers match part is perfectly fine. When numbers don't match, then you know for sure it's bad.Then you'll only have to replace one part that's bad to fix problem. This is how professional and dealer mechanics work. They don't have entire warehouses full of spares for every model ever made to swap randomly. Testing and measuring is fastest and most inexpensive method of troubleshooting.

Now, have you measured for +12v going to each coil with key ON? Wouldn't surprise me if #4 doesn't have power going to it.
Have you measured resistance of each wire between coil connector & ECM connector?
Could be bad connector or corroded terminals. Or mice may have eaten a wire.

 

12 volts To #4 Coil ..And To All Others.Replaced all 4 Coil Connections Crumbled In My Fingers...( All Wires Are In Correct Position)..... 12 volts To All Fuel Injectors.....Check All Cylinder Pressure Wet/ Dry All Within 10% ......The tC Will Run But Only On 3 Cylinders, #4 Will Not Fire

I Also Set A Mouse Trap .......

 

2. Ok, what is resistance end-to-end of each coil's trigger-wire from ECU to coil-connector?

3. Next up is testing for coil-trigger signal on all coils. Use 'noid light to test for grounding-pulses from ECU to each coil. Does it flash for every cylinder?

 

Thank You For Indirectly ( Sort Of) For Finding The Problem
To Go Over Again Everything I’ve Done, And To My Wife Who Told Me This Morning.... KISS It..( Keep It Simple Stupid)...🤦‍♂️, This Thread Has Been So Helpful 😎