No Start, OBDII Fail to Communicate
'08 Cobalt Manual Trans: NO START, OBDII FAIL TO COMMUNICATE.
When I say "No Start", I mean it doesn't even turn over, nothing happens.
I've read enough forum pages to feel like this is NOT completely covered. First, OBDII works, I've gotten codes on this car with this device a month ago, but not any longer, connected it to my Suburban today to verify because that seems to be the number one response. Second PCM (ECM) is bad, seriously doubt that, I just bought it and it was already flashed from gmflash.com. Third, battery is strong, connected jumpers to my Suburban (with Suburban on) just to be sure.
Recent driving history, going down the road it would randomly start shuddering or feeling like it was firing on only two cylinders, so shift to neutral shut off and restart, problem temporarily solved. Eventually the tach started shutting off, and then instead of shuddering the motor would just shut off, same remedy, neutral & restart. One day it wouldn't start in the morning. I scanned it, and it indicated the evap canister, which was replaced by the dealership last year, and (thanks to forums) shouldn't cause a no start. Because it was a gradual decline in performance and didn't fail to start "just out of nowhere", I bought an already flashed PCM (ECM), my Suburban (last month) was doing similar things including the no start but not the OBDII- "Fail to Communicate", everyone and every forum said it's not the computer, guess what- it was. Dropped it in and it fired right up.
What I've done: checked EVERY fuse inside and out, continuity from PCM housing to chassis, start relay bypass (turns over-still no start), clutch switch bypass (did nothing), checked chassis grounds, ignition cylinder was replaced due to recall, anti theft works and turns off with the key. Also before the no start I switched the #1 coil pack with the #4 coil pack because I read on a forum that the #1 might be going bad and that's the one the computer reads, but that did nothing to improve things and eventually I suffered the no start.
Last edited by Mike Hunt; 12-28-2017 at 02:49 PM.