2013 Expy (220K miles) with a crank but no start condition. Getting codes P1636 and P2107 (also a couple for the O2 sensors but dont seem to be related). Was driving down the road, and it suddenly just shut off, like someone killed the power. No stumbling or strange noises (like a timing chain or something). Has a brand new fuel pump. So far have tested and have fuel up to the fuel rail, have spark at the plugs, and the crankshaft position sensor seems fine, as i get a reading of 150 rpms on my scanner when turning it over. I have not checked for compression but figured based on circumstances that is not the issue. I have tried to "reset" by leaving battery disconnected for a couple of hours. I have visually inspected the wire haresses that come off the PCM under the hood, and nothing jumps out, but everything is still in the protective sleeves, and dont see any signs of damage or cause for concern when checking that. Worth noting that if i let it sit for a few hours, and try to start, it will usually start for about 0.75 seconds, just enough for you to think yeee.. oh. I have searched quite a bit online, and most posts i see with both of these codes indicate needing a new PCM, or testing out any of the items already mentioned above. I have NOT taken the front of the engine apart to check the timing chains, and not afraid to, but based on what I have found and what happened initially, it doesn't SEEM like a timing issue. Wondering if anyone has had similar issue or is familiar enough with it to offer any advice. I am willing to replace the pcm or the timing, but want another opinion about the PCM as electronics like that are typically not returnable once you have used them. Appreciate in advance any suggestions or advice.