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Discussion Starter · #1 ·
I was off to get new tires installed, and another issue came up.

No spark off of either coil pack. Looking at the Infinity datalog, it gets the sync signal so I think that means the cam and crank sensors are working, and that the Infinity is getting power and is on. The injectors are squirting fuel. There's no engine protection flags on the data-log. I swapped the ASD relay with one of the other ones, and also checked it's operation with a meter. No fuses are blown. The battery is charged.

Anything else I should check?

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Discussion Starter · #16 ·
I'm pretty sure the Infinity is the issue. I've checked continuity from the Infinity to the ignitors to the coils. The coils are getting the battery voltage on pin 3, about 9-10V when cranking. The coil outputs from the infinity have no activity on any of them.

I wanted to put the stock PCM back in and see if it can make sparks- that would almost prove that the Infinity is the problem. The Infinity uses different sensors, or the same sensor with a different connector, for the following:

1. Cam sensor
2. Crank sensor
3. MAP- ignored if sensor isn't working, uses TPS and RPM to estimate plenum vacuum.
4. Fuel pressure- not used in the stock PCM
5. Intake air temp- default temperature used if sensor isn't working
6. Knock sensors- not used in the stock PCM(?), and not used during 'start engine'.
7. O2 sensors- not used in 'start engine' mode

The TPS, idle control, and coolant temp sensors are the same in both systems. This leaves the two angle sensors.

Anyone know if this is right??

Unfortunately it still doesn't activate the spark plugs. So either there's at least one sensor that the stock PCM does need but it's seeing, or whatever is preventing getting a spark is common to both the stock PCM and the Infinity and that's what needs to be fixed.

I should add that if the Infinity is the problem, AEM no longer fixes products that are out of warranty. So I'll have to fix it myself or buy, install, and tune a different ECU...:rolleyes::cry:
 

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Discussion Starter · #22 ·
I did check the ASD relay, swapped it with one of the other, less often used relays. Even took the PDC apart to fix some of the contacts that weren't grabbing onto the relay pins very well. Checked all the fuses.

The cam sensor signal was almost a perfect square wave, 0 & 4V. The crank sensor signal has pairs of pulses, caused by the 54 then 90 degree separation of the cylinder firings. I didn't take a long enough sample to see a whole 720 degrees, but it's really likely that it's working right. I'll get a full 720 degree sample anyway...
 

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Discussion Starter · #25 ·
I've checked the voltages at the relays and jumpered the relays too. No change.

I've looked at the AEM coil outputs at the inputs to the ignitors, which is the AEM output pin + a wire. None of them show any activity. A five point failure is unlikely, so what probably happened is something common to the 5 coil outputs failed and so none of the cylinders are getting any spark. The coil output signals from the AEM all come from the same IC driver, so it's possible that one of them going wonky broke the whole IC. Something did pull a lot of current when this happened, because the 20A ASD fuse blew.

I've reflashed the firmware twice, once updating it from v96.2 to the latest, v96.5, then went back to v96.2. Apparently the tuning data format is different in the updated v96.5 version. While it can be made to convert it automatically, I wanted to go back to the original version and use an unedited tune file. No spark in either version.

I'm going to look at the inputs to the coil driver IC in the AEM next, if there's signals there, and I know there's no signals coming out of it, I'll replace it and it will (should, might, maybe, probably won't) run again.
 

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Discussion Starter · #27 · (Edited)
A couple posts up I did mention that I'm seeing the battery voltage on those pins. I know it doesn't come from the AEM, I have the service manual. And it's not 12V- this is when the starter is running so the voltage drops down to 9 or 10V.

I've checked all the fuses. The ASD is the only one that blew and it's been replaced. I also checked the ASD relay. It's working.

The coils are driven by the ignitors which are driven by the IC in the AEM, it's just a basic 5V driver. This is different than how the stock PCM works, as you noted :)
 

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Discussion Starter · #32 ·
I fixed it. The problem was in the Infinity. I opened it up and looked at the waveforms going into the coil driver IC's ( 74AC541 line drivers) . The amplitudes looked too small, 2.76V with 5V logic, which could mean that whatever is driving the coil drivers was bad; despite that, I decided to replace the coil driver since there are two of them (each one drives 5 coils, so one of them wasn't being used), and to my shock and amazement, it starts now.

Thanks for all the advice and offers for help. Now to figure out the fuel pressure problem, if it still is happening.
 

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Discussion Starter · #35 ·
Sorry, I should have been calling them ignitor drivers. The ignitors drive the coils and the IC I replaced drives the ignitors. The Infinity uses ignitors between itself and the coils. No MOSFETs in the Infinity for the sparks, there might some in the ignitors though.

Yes, it can drive up to 10 coils from 2 IC's, 5 each. So I removed both of them and soldered the good one where the bad one used to be.
 

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Discussion Starter · #36 ·
The 2.76V is barely enough to be recognized as an input 'high', so that's why I though the prior part in the path was the problem- it should be up at 4V or even 5V amplitude. However the bad ignitor driver may have been affecting the input voltage amplitude, making it lower than it normally is.

I don't have a schematic either. I did ask AEM and Engine Labs for one but not surprisingly, they couldn't let that out- proprietary, confidential, etc. It was a long shot.

At any rate, it works now. I'm going to order a new ignitor driver IC and put it in. Taking the good one out involved a LOT of heat and some bending of the leads, I wouldn't trust it to be very reliable.
 

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Discussion Starter · #38 ·
ID #? You mean the P/N? There are two, 4 channel ignitors. One uses three of the four, the other uses two out of four. A case of up-selling the customer- they could have used two of the 3 channel versions. Grrr.

If you mean something else, I have them on a heatsink and a mounting plate with thermal grease, bolted together and Loc-Tite'd. I can see the P/N but that's all. If you really want to know what's on the back, I'll unmount it...
 

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Discussion Starter · #39 ·
In the unlikely event that someone else needs to replace one of these, make sure to get the correct package type- SOIC (small outline IC). I had actually ordered and received them, only to find I'd goofed and ordered the wrong package. Currently these parts in the correct package are on backorder, none available until early 2023.
 
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