ecu grounds

I've got a 2010 toyota tacoma 2.7L with a intermittent no start when it is hot soaked. I have narrowed it down to a loss in spark (igt signal from the ecu). I have a good cam and crank input signal to the ecu. Proper Immobiliser input and output to the ecu. As i scope the igt signal outputs from the ecu, i would get 1-4 igt signal output randomly cutting in and out intermittently, causing an extended crank or a no start. As i check my computer grounds during cranking i get 600mv as a maximum reading. Is that an acceptable voltage while cranking??

600mV? That does seen excessive... Are you measuring this with a multimeter?

If you wanted to prove that out, you could try adding a redundant ground to the wire you're seeing high voltage on, and see if the readings improve. If your hot soak symptom goes away, then you're on the right track

thx for the reply. I used a scope to measure it. I did add a few extra ground. The weather is a bit cooler where I am. Im just waiting for a nice day to see if it corrected this problem

Gotcha. I do sometimes see higher spikes on a scope trace during cranking, but they're very fast, and mostly amount to noise. Yours sounds like a more steady, consistent reading.

Thanks for keeping us updated!