Im sorry if this thread has already been discussed I've searched and nobody has reall gave a full answer!!! So I have 2003 blazer xtreme Ive only had the truck for a week and I drove it from Ga to Nc and the water pump started leaking goin down the interstate and check engine light started flashing so I had code checked and it turned out to be multiple cylinder misfire so I figured water might of dripped on the crankshaft sensor triggering it so when I got home I changed water pump and reset ecu(PCM) light went off I've been driving it around town everything seems to drive fine until I bust down the interstate and when it hits 80 the light starts flashing then when I back off 80 it quits and goes out I'm very upset with this truck I've changed plugs, wires, cap, rotor button, coil, and fuel filter I'm all out of Ideas I'm thinking the water might of fried my ckp but it's not showing a code any help would be appreciated!!!! Thanks

 

A flashing SES light means that a potentially damaging misfire condition exists. The presence of the P030x code confirms that. Check out the OBD2 trouble code section for some ideas on what could be causing the problem and how to diagnose it properly. You likely have an ignition system problem that is causing the misfire.

Your CKP sensor should not be affected by dripping coolant. Its connections are water tight.

 

That's what i thought also I'm really confused I'm gonna go to school and get on alldata and look up some stuff on it do you think it may be a faulty distributor??

 

One thing I have learned about the P030x codes over the years is that it can sometimes be the most obscure problem that is causing the condition. From my experience, anything in the ignition system could cause the condition.

Was their freeze frame data along with the code? Under what conditions is this occurring (RPM, Speed, outside temperature, outside conditions, etc)?

The coil & ICM are fairly straight forward to test. EasyAutoDiagnostics.com has the relevant procedures for testing a number of systems on the 4.3L engine.

 

It don't never flash until I hit 80mph any weather condition a friend told me that water from my pump may of leaked and corroded the terminals on the crank sensor and may not be sending all 5 volts to the 5 PCM!!!

 

If you want to go down that path, then get at it. It's easy enough to check the connection on the CKP sensor. A little coolant dripping here and there is nothing like driving through a rain storm.

 

But either way do you think it's ignition related?? I just hope it's not internal!!!

 

Yeah, I do think it's ignition related which is why I pointed you towards information relating to testing the ignition components.

 

Did you ever fix this because i have the exact same problem im trying to solve?

 

Actually I did find out the problem...it was a bad spider injector!! what happens is your going so fast you can't feel it misfiring but at idle and cruising you could feel it but it would never throw a code until i hit 80mph I replaced it with a used injector and it was perfect but I ended up selling so if your gonna keep it you need to replace it with a gm one they upgraded them for better fuel economy cause there sequential now and last a lot longer!!! Hope this helps...