Toyota Igniter Failure
It's always interesting to learn that even when you've seen a particular issue on a given manufacturer's vehicles, it doesn't necessarily manifest itself the same way on all models or years. I was called out by one of my regular customers to look at his girlfriend's car. She'd been driving on the highway when the car started running rough and losing power before stalling completely. Afterwards the car would start and run for a second or two before stalling once more. When I did my initial scan, there were multiple codes in the system for EVAP, lean run, and the P1315 along with a P0304. After doing a visual and not finding anything that looked particularly dubious, I pulled up some data pids while attempting to start the engine. Sure enough it would start and stall after a couple seconds. Nothing in the data seemed unreasonable and I thought perhaps that #4 igniter was causing problems but to my surprise, the engine wouldn't stay running with the #4 coil unplugged. I've most definitely run into c.o.p. Toyotas with single igniter failure but never one that wouldn't run. Generally the vehicle in question would simply have a dead misfire. Further research revealed that if any of the four igniter feedback signals was not being received for 4 consecutive cycles, the pcm shuts off all the injectors as opposed to just the one for the offending cylinder. A quick swap of the coil to cylinder #1 proved that the fault followed the coil. I wanted to see this in action though so I hooked up my labscope to all 4 inputs of the #4 coil (which was originally at #1) The first picture shows the few seconds of run time with the bad coil. Knowing the firing order and the fact that what you're seeing is a capture from #4, you can count the IGF signals and see that #1 is missing competely. In the end, the customer decided not to fix the car (I can't explain that one) but I happened to have a good used coil from an '05 Sienna. While they aren't identical, it was close enough and of similar function for me to temporarily install it and prove that the car would start and run. The second picture shows the running Corolla with all 4 IGF signals intact. I haven't done the research to confirm this but my assumption is that Toyota revised their operating strategy in later years such that the pcm only shuts off the injector to the offending cylinder instead of to them all. I know I've replaced coils on Corollas before, but I must've never encountered this type of failure on one of these. I'm sure many of you out there are thoroughly familiar and will not be surprised at all. I found it interesting and thought I'd share nonetheless. Thanks for taking the time to read this, Happy Friday Y'all!
Wow, that is certainly odd to me. Been ages since I saw a Corolla (although the model year is right for most cars here), but I remember one time having a Camry setting a false "IGF signal missing" DTC, and running just fine with no misfires. Seems the different failure "reactions" of the ECM are endless as these things age. Also I think you "typoed" one sentence; you wrote "you can count the
Yeah I thought it was really odd too as I've seen the same. I've had c.o.p. Toyotas with igniter codes that had an active misfire and also ones with these type of codes that ran perfectly as you describe. My assumption is that this was an early version of the kill the fuel to save the cat logic. Perhaps Toyota realized that it was dangerous to have the car just shut off due to something this