These cars are known for a ignition switch malfunction, but the symptoms were slightly different (the security light did not flash*).
- Everything seemed to power up but would not crank.
- PWR STR, SERVICE VEHICLE, and COOLANT errors were displayed on the dash.
- I was unable to connect to the OBD2 bus.
The Battery is located in the truck. There are 2 positive wires running from the battery forward. the big main one to the starter motor and fuse-box and a smaller one with an inline fuse holder several inches from the battery which apparently goes directly to the ECM.
- The spare tire compartment had about 1" of water setting in the bottom which submerged the connector just after the inline fuse.
- The wire corroded off both sides of the connector, shorted and blew the fuse.
- Twisting the wires together and replacing the fuse resulted in a running car. The wires were soldered.
- The Check engine light was on however with a code p0315 Crankshaft Position System Variation Not Learned. According to most websites, solving this requires a "CASE Relearn Procedure"on GM's Tech2 scan tool. Apparently it will never clear itself. However there are several aftermarket scan tools that can do this. I happen to have a TriCAN from www.obd-2.com. I love this tool, it does a huge amount of things many expensive hand held units don't. It has it's downsides though, it requires the use of a laptop, and in this case I could enable the CASE Relearn, but had to figure out what to do next from forums, etc.
The CASE Relearn procedure
- Bring coolant temp up to 158F+
- Shut off car
- Wait 10+ sec
- Start car
- Hold foot firmly on brake from now on
- Enable CASE Relearn
- Steadily increase RPM until it hit's the (lowered automatically by the test) rev limiter at 4000RPM
- Remove foot from throttle immediately at the first blip
- MIL should go off at this point
- Clear code (stays as historical)
Always check the simple stuff, I spent several days hunting for problems up front because the truck was so full of junk I couldn't even look at the battery. I assumed that as long as i had power up front the battery area was fine. How wrong I was...
Oh, wiring diagrams are your friend.
* If your security light is flashing you probably need a new ignition switch, they are a very common problem.