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Discussion Starter #1
So after finishing my DOD delete and manual swap, the car runs but throws codes po355 po356 po357. Seems like cylinders 5 and 7 won't fire even when a known working coil and plug is swapped in.

Ground on the rear driver head, and front passenger head are good and tight. I don't think I messed with any other grounds iirc, at least not any that I'd think would affect this.

Anybody have any ideas?

Thanks,
Zack
 

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That's a selection of codes that say those coils are not getting their required voltage (to spark correctly). I'm pretty sure that the loss of the ground return from those coils, would produce the same results (even if the voltage from the ECM was good). Your sure that the wire loom from the 1-3-5 an 7 coils) which is routed behind the cylinder heads to work there way around to the passenger side cylinders has not been compromised.They pick up the added wiring from the passenger side, an continue forward an down to the ECM. Cylinder #6 is as big a mystery as #5 an #7. You could verify that all the coil ground wires are good using a meter >>>>> The primary coil uses pin B (Brown in color), an goes back to the ECM to an internal ground source (all 8 of them). The secondary coil uses pin A (Black in color). The drivers side uses a ground location at the rear of the cylinder head on that side. The passenger side uses the ground stud location at the front of the cylinder head on that side. An all of the wires on each side make a pass thru at those center mounted 7 pin connectors before moving on. If those 2 connectors were disconnected during the rework, there's another location that could be the source of the problem.
 

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Discussion Starter #3
Your sure that the wire loom from the 1-3-5 an 7 coils) which is routed behind the cylinder heads to work there way around to the passenger side cylinders has not been compromised.They pick up the added wiring from the passenger side, an continue forward an down to the ECM. Cylinder #6 is as big a mystery as #5 an #7. You could verify that all the coil ground wires are good using a meter

>>>>> The primary coil uses pin B (Brown in color), an goes back to the ECM to an internal ground source (all 8 of them). The secondary coil uses pin A (Black in color).

The drivers side uses a ground location at the rear of the cylinder head on that side. The passenger side uses the ground stud location at the front of the cylinder head on that side. An all of the wires on each side make a pass thru at those center mounted 7 pin connectors before moving on. If those 2 connectors were disconnected during the rework, there's another location that could be the source of the problem.
Where are the "A and B pins" you're talking about?

I know the ground connection at the rear of the driver side and front passenger side head are on right but I'll probably undo them anyway and reconnect after cleaning the connection points again.

I'm 99% sure I know what you're talking about with the two center mounted 7 pin connectors. They have a little hole that a plastic table goes into to keep them from coming apart. I did disconnect and reconnect those in the build process. Are you saying to disconnect and reconnect them again?
 

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If you had access to a timing light gun (you could do it the simple way). You would just power it up from the battery jump posts, position the pickup coil lead around each high tension lead that is giving you trouble, an see if it would flash/strobe each time that cylinder was commanded to fire. Each coil connector has a 4 pin connector. The black wire is in pin A an the brown wire is in pin B of each connector. Those are the ground wires that must be in good condition. You are correct about the 7 pin connectors. As long as you're sure those connectors are in good shape an reconnected properly, I guess you could eliminate them. But any breakdown from one or more pins from those connectors, could be part of the problem.
 

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Discussion Starter #7
Cool. And I just point the light gun at the harmonic balancer, pull the trigger and it'll just light up when good things happen? I've never used one before but I'm sure I can get access to one

What exactly is that going to do if I already know cylinder 5 and 7 aren't firing and that putting a working coil in their place doesn't change that? Just trying to understand
 

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Once you clamp the lead with its wrap round clamp around a plug wire, start the engine, pull the guns trigger, an point the gun at anything that will bounce the flash (or point it at your eyes an watch its cycling flash). If *it* flashes, it proves you are getting spark to an thru the plug. You could start with a known working cylinder to see the action I'm talking about. Then move on to your troubled cylinders. Based on the fault codes, you would expect that *no* flashing will be taking place on those 3 cylinders. If that happens, your back to finding out why those coils cannot build up an discharge their voltage spike.
 

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Discussion Starter #9
So I cleaned the hell out of the grounds and got them good and snug.

I checked continuity from all the injection coils to the ECU.

Checked continuity from the coil B ports where all passenger side b ports had continuity to reach other and all driver side b ports had continuity to reach other. None of the passenger B ports had any continuity to the driver side B ports but I think it's supposed to be like that???

Checked all the A getting ports to ground.

Everything has continuity like it should.

I swapped known working coils and their plug wires with the non working ones. I cleared the codes in the car. I turned the car on and it ran like hell (seemed to run okish they other day). I got the following codes

Po357 ignition coil g primary/secondary

Po208 cylinder 8 injector malfunction

Po205 cylinder 5 injector malfunction

Po122/po122pd(?) Throttle position sensor

P0222 and po222pd(?)

All headers are hot except 5 7 and 8
 

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Are you sure that the TB connector is OK wire wise an latched to the TB ? Those codes are saying the TB is experiencing low voltage. Think you better disconnect all of the injectors, turn on the ignition, an check for 12 volts showing up at at pin A of each of them (drivers side wire is pink/dark blue an the passenger side wire is pink) If OK, you may have damaged ground return wires going back to the ECM to energize the injectors
 

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Discussion Starter #11
I checked for 12v at the coil connectors and fuel injectors for cylinder 1 5 6 7 8 and they all checked out fine.

When I saw throttle position sensor I thought it had to do with the gas pedal but I guess not then? I might try to check the throttle body but I feel like all that is fine but hopefully it's not so I can take care of it 😂
 

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I hope it's not bad etiquette to jump in on a thread but I have a similar problem. Just finished reinstalling the engine on my G8 GT after DoD delete (and other work.) I actually missed two grounds when I was hooking the wiring harness back up - the big ground from the ECM to the ground stud on the front of the right head and the coil ground for the left bank coils on the back of the left head. Without the ECM ground connected, of course, the engine wouldn't even crank. (I think that I should have gotten a P0606 code at this point but I didn't.) After I found and connected the ECM ground, the engine started and, believe it or not, ran with good spark on 2 and 8 and intermittent spark on 4 and 6. Found and connected the ground for the left bank coils and thought all would be fine. Not quite. At that point,#2 & #4 coils were not firing at all and I suspect (because of exhaust manifold temps) that others are firing intermittently. After reading this thread, I carefully cleaned the contacts for the 4 pin coil connectors and the 7 pin connector. I have good grounds on both the A and B pins on the connectors for #2 and #4 coils. However, I still have no spark on #2 and only intermittent spark on #4 (which is at least a slight improvement.) Interestingly, I'm not getting a misfire code (P0301 thru 0308, I think) and I'm not getting an Ignition Coil Control Circuit failure code (P0351-0357). I think that my code reader is working and communicating with the ECM because I'm getting that pesky P0449 Emissions Purge Valve code that I just can't seem to eliminate.

Which pin on the 4-pin connector supplies the voltage to fire the coil and how would I check for proper voltage? BTW, I did order another coil just on the off chance that the #2 coil could have somehow gone bad in this process. Worst case scenario, the old coil will not be the problem and I'll have a spare. Hopefully, I'll know tomorrow.

Thanks in advance for your help.
 

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Since "zygee" seems to have elected to drop out of sight (so to speak), I don't see any problem with you continuing this Thread, since its pretty much the exact same type of problem. Those codes assigned to the coils (P0351-P0358 along with the miss fire codes P0301-P0308) are B rated codes. They would display those faults only after 2 consecutive start/run cycle failures were sensed. If you forced a reset after each start/run cycle, the 2 cycle requirement would never be reached. The coil power shows up at pin D at each of them, once the ignition is turned on to the full on position. That same power source also powers up the injectors at pin A. The coils receive their timed coil pulse/power (from the ECM) to discharge the coil voltage to the plug thru pin C (thinking you have to trust that (that) function is happening. Course if you have a timing light gun (or a wraparound tool that would produce a strobe flash) that would be the easiest an best way to see how the coils are performing. Any failure of a coil or injector to pulse correctly, creates the condition for a miss fire event. All the injectors are hardwired to the ECM. Any one or more coils receiving its pin A power, would indicate that the power made it thru those 7 pin master disconnect connectors.




I'll study the purge valve circuit in the manual, then add some info to this post, if it looks like it would help.


Added info----- The P0449 code is for the EVAP canister *vent* valve. Its saying the valve *did not* move to its commanded position as requested by the ECM. If its telling the truth (an does not heal itself), your in for a painful R&R job unless you can get it deactivated/removed from the EVAP monitoring system.
 

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Discussion Starter #14
I just figured everyone had run out of ideas like I had 🤷‍♂️

Throttle body connector checked out fine. When threw on a known working throttle body from another car which made no difference.

Only thing I'm not sure of is whether the 5v reference is only supposed to have voltage when the car is running or if it's supposed to have voltage at all times and/or with the key turned to the on position. With the key in the on position and with the key out I didn't have voltage at that 5v throttle body reference.
 

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^^^^ What codes do you get at this time ? How many of the coils demonstrated they were firing off correctly when using the timing light ? The TB receives the 4.8 to 5.2 volts on pin E (gray wire) from the ECM whenever the ignition is turned on. Your saying you *do not* have the 5 volts DC at pin E when reading with a meter from that pin to a known good ground source ?
 

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Discussion Starter #16
^^^^ What codes do you get at this time ? How many of the coils demonstrated they were firing off correctly when using the timing light ? The TB receives the 4.8 to 5.2 volts on pin E (gray wire) from the ECM whenever the ignition is turned on. Your saying you *do not* have the 5 volts DC at pin E when reading with a meter from that pin to a known good ground source ?
I didn't bother with a timing light since I had codes for the specific coils that weren't working for whatever reason and those were the only cylinders with cold headers after running the engine.

That is correct though, with the plug/connector disconnected from the throttle body and sticking a probe into pin E I was showing no voltage with the key in the on position and the engine off/not running
 

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Discussion Starter #17
After clearing codes I know for a fact the following two codes come up immediately regardless:

Po122/po122pd(?) Throttle position sensor/switch A low circuit input

P0222 and po222pd(?) Throttle position sensor/switch B low circuit input


I think there's one more for a ignition coil or something but I'm not sure for a fact and may be wrong on that.
 

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I guess this means you have concluded that all of the coils are working correctly (so be it). All 6 wires to the TB are hard wired from the ECM. If stepping on the throttle pedal moves the TB blade open an closed, those 2 wires (from the ECM) must be OK. The remaining 4 wires are for powering up the 2 TB position sensors as well as sending back their variable voltage outputs, back to the ECM. If those voltages are lost, I'm sure that is what gives you those TB sensor fault codes (an probably lousy running engine). You would hope that the ECM is actually sending out the 5 volts to pin E for the TB. If not, the ECM has a problem. If it is, but not making it to the TB, you have think that the wire is broken/open somewhere between the 2 locations. I know that tiny wire loom is tightly wrapped an breaks out from a larger wire loom so as to attach to the TB. But it reads like you'll have to open it up as far back as necessary (an with a meter) probe that gray wire insulation at various locations until you can find that missing 5 volts.
 

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Discussion Starter #19
I guess this means you have concluded that all of the coils are working correctly (so be it). All 6 wires to the TB are hard wired from the ECM. If stepping on the throttle pedal moves the TB blade open an closed, those 2 wires (from the ECM) must be OK. The remaining 4 wires are for powering up the 2 TB position sensors as well as sending back their variable voltage outputs, back to the ECM. If those voltages are lost, I'm sure that is what gives you those TB sensor fault codes (an probably lousy running engine). You would hope that the ECM is actually sending out the 5 volts to pin E for the TB. If not, the ECM has a problem. If it is, but not making it to the TB, you have think that the wire is broken/open somewhere between the 2 locations. I know that tiny wire loom is tightly wrapped an breaks out from a larger wire loom so as to attach to the TB. But it reads like you'll have to open it up as far back as necessary (an with a meter) probe that gray wire insulation at various locations until you can find that missing 5 volts.
So when I actually turn the engine over and it turns on I can press the throttle pedal and get the RPMs to move and hear the response from the engine so I'd assume that means the TB blade is moving (since I didn't have somebody visually inspecting it as I did that).

While pin E doesn't have voltage as described above, my multimeter does indicate continuity between pin E and it's corresponding pin on the ECU. I think somebody mentioned that is still possible even with a disconnect somewhere somehow.

So if the mechanic I've sent it to doesn't figure anything out by next Tuesday I'll start probing from where the 5v reference wire leaves the ECU up to the TB connector in search of voltage.

Also in regards to using a timing light to check the coils: As an honest question, if the car is running and the headers are getting hot on all the other coils (even when I swap the coils from the problem cylinders with ones from cylinders that seem to be working) what could be wrong with the cylinders/coils that seem to be working fine and how might that change the troubleshooting process?
 

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Any coil that works in one location, means *it* will work at any of the 8 locations. If there's a voltage or ground problem that is present at any of the 8 coil connectors, none of your coils (or anybody else's for that matter), will work at that location. Same goes for any injector. You'll just have to find that missing 5 volts to the TB an correct same, before you can get a good checkout of the 8 cylinders. At least that's my opinion.
 
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