Hey guys/gals Working on the wife's car. Radiator leaked, so I replaced it. Started right up with no issues. Wife wants to talk, so I shut it off. After her talk I get an intermittent no crank. When it will crank I get the full 12.2 volts to the starter. When it wont crank, I can hear/feel the run/crank relay click, but not the starter relay. After looking at a few things, now when I plug in my scanner, it shows no communication from the ECM. From what I see, when you turn to crank it sends a signal to the BCM, then a request to the ECM, then to the run/crank relay, then to the starter relay. The small bits of wiring diagrams i can find says that the info from the two relays is inside the fuse block, which sounds weird, but weirder things happen. remove the underhood fuse block to check for corroded terminals, heated and burnt plastic block, etc. Nothing. Recheck and still not getting any power to the starter. Hmmmm? any ideas? Now when I removed the radiator for replacement, I made the mistake of pulling the fan assembly, not realizing that the radiator came out from the front side of the core support, not the rear. I did break a wire doing this, but I repaired it properly, including heat shrink tubing. I inspected all the other wires and found no issues. The wire harness that is in question does NOT contain the purple starter solenoid wire.....
2.4 4 cylinder

 

What engine?
You can find it in here.
https://charm.li/Saturn/2008/

 

UPDATE: Now it starts almost every try, but my scanner still reads "unable to establish communications, be sure the key is in the run position", and the check engine light is on, but I cant read the code due to no communications. The dash says "power steering", but the power steering seems to be working just fine. Also the atmospheric temp is "---" and the tire pressures are "---". Just weird

 

Pull the fuse block again.
WIth battery disconnected, clean w electrical contact cleaner. Both the panel and the block terminals.
It sounds like you have lost either power or ground somewhere.
If you disassembled the fuse box and put it back together with different results, I'm thinking it's a poor connection or connections between the panel and the block. You also may have disturbed a ground at the block.

Do you have a wiring diagram?
What engine is this?
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When the radiator leaked, where did the coolant land? Basically I'm asking if any coolant, and or any distilled water, could have found its way into the fuse box or in contact with any of the wiring harnesses leading to or exiting the fuse box.

 

Sorry, I editied the post to say 2.4, 4 cylinder engine. Radiator replace because the original hose clamp was broken. Ive never seen this before, but the original spring type clamp, one end rotted off and broke, causing a very slow leak at the passenger side of the radiator. Very good thought, but no coolant touched eighter the ECM or the TCM. Coolant on the passenger side was too far away from there, and coolant was drained via the radiator hose by radiator hose removal on the d rivers side, and went straight down, not onto the ECM or TCM. I do not have a wiring diagram, but that would be helpful. Very helpful. If you know where I could get one, that would be great. When I removed and inspected the under hood fuse block, I also moved, but did not unplug the ECM, to look for wire issues. Yes, it could be fuse block issues, but could also be wires to/from the ECM. Engine is still starting ok, but I do not trust it since I havent actually found an issue. Check engine light is on, with "failure to establish communications" comes up on my scan tool. Im thinking Im going to remove all the conduit from the wiring harness that I may have harmed when removing the fan assembly, for detailed inspection.
To reiderate the issues: intermittent no crank/start, no comunications from the ECM, check engine light is on, and dash shows missing info from tire pressure and atmospheric temp. To me this sounds like ECM and BCM issues.
Any help or thoughts are appreciated.