Disconnected the two coils and hooked the terminal for the rear (1 & 4) coil to the front (2 & 3) coil. Cylinders 2 and 3 fire once. Cylinders 1 and 4 didn’t fire, obviously, because the coil was unplugged. This effectively emulates a coil swap without unmounting the coils. Suspecting it’s the ECU.

New ECU purchased from eBay to the tune of $20 with shipping. I had the 89666-06121 installed but have purchased an 89666-06120.

 

Bumping this thread. New ECU has the same behavior.

Next step, I suppose, is to trace that wire back to the ECU and make sure there's good continuity / near-zero resistance on that wire in the harness.

 

i don't recommend using numbers other than the ones in your car from the factory but there are subs allowed as long as you understand what they are. 20 bucks seems kinda cheap for a good ecm but i guess it could be fine. does your car use an igniter or does the ecm have 4 drivers for each plug and drivers the coil itself? if you have an igniter, then i'd suspect that. if the ecm directly fires the coils, then time to do loaded voltage drop tests or even continuity checks on each of the suspect driver's leads.
tony

 

I'd suspect coils. Swap coils - they are the same except for numbers printed on them. Camry has wasted spark system, so both 1 & 4 fire every time either 1 or 4 needs spark, same for 2+3 coil.
It's a bit of a pain in the ass to get to some of the lower bolts, but totally doable. If the problem moves with the coil, you have a bad coil. If problem stays with same cylinders, I'd suspect wiring - maybe you pulled the harness somewhere when pulling the engine and damaged the wires.
If you need new coils, I have a set of Denso coils with 200 miles on them (mis-diagnosis on my part, so ended up with extra parts...). I'll make you a good deal.
Hope this helps.

 

I tested the resistance on the secondary side of the coils and it was in spec per Haynes manual, and I didn't unmount the coils but moved the plug from the front coil to the rear coil, which moved the single spark to cylinders 2 and 3. Thinking it might be a damaged wiring harness.

$20 seemed cheap but it seems to have the same symptom, and I don't think they're both bad in the same way. My brother swapped it -- the car's about an hour away from me. I'll have to look into the possibility of it being the igniter. There's two separate coil packs and two plugs from the engine wiring harness to the bottom of the coils, so I think it's the latter. Any resources on voltage drop tests and where to look for continuity?

 

If you moved the plug wires and the issue moved with the coil, then wires and plugs are good.
You're left with either bad coil, wiring issue, or ECU issue.
Coils you can check by swapping them like I said above. Easy. These are integrated coils/igniters.

For wiring, you have constant 12v (with ignition on) and ground, IGT and IGF.

IGT is ignition trigger from ecu. 5v that is grounded when spark is to occur.

IGF, white-red wire, is Ignition Verification Signal (IGF). The coil grounds this signal when ignition has occured to provide feedback to ECU. If this doesn't happen then ECU considers it a misfire.



To check wiring you need to substitute a load, not just test it with a multimeter. A headlight bulb will do. You need to check whether the power and ground can supply a couple of amps. A broken wire can supply enough to show voltage on a multimeter, but will drop out under load. The wiring to ECU should be checked same way - with a load on the wire.

ECU is unlikely. You can test it, but will need more sophisticated tools to do so. Either scope, or at least duty cycle meter to check IGT signal. It may be that if IGF does not provide confirmation to ECU the ECU will cut out the cylinders, though I'm not sure about that.

 

slavie, you're correct. if the ecm don't get proper feedback via the loop, it'll stop firing that driver.
tony

 

Hope I can still bump this thread. I got out to the car today with an oscilloscope and a replacement coil. First, replaced the coil with a brand new one. Same behavior. Assuming it’s not the coil, put the old one back on.

I took a paper clip and shoved it into the back of the plug going into the ECM for IGT1 and IGT2 and I saw something surprising. I expected to see IGT1 rising normally and IGT2 rising only once. What I saw was they both rise as you’d expect, but IGT2 only falls about halfway to ground in between firings.

Sorry for potato quality, but here’s the scope:
https://imgur.com/gallery/vEbktFX

Jeez. What could make that happen? My theory is either a bad ground wire failing to bring IGT2 down to ground in a reasonable time, because of the somewhat sawtooth-esque pattern with rapid rise and gradual but incomplete fall.

At this point am I looking at a new wiring harness?

 

Did you figure out the issue? Having the exact same problem

 

Hello, I just TS my friends Camry with no start, check your IGT and IGF signals, my buddies female connections of the igniter were slightly stretched out, causing a bad connection, had near identical read out for injectors, spark 1 time then not again.

Your vehicle is in safety mode because no spark (IGF) signal is getting to the ecu so to prevent flooding of the engine the ECU cuts the injectors.

Check your IGT at igniter and IGF, let me know what you get for a signal when you crank with test light.