I have a 01 silverado 2500hd with 168,000 miles. My service engine soon light is coming on and flashing after I am on the road running at 70mph or faster. I took it to my mechanic and he did a all over tune up and it still does it, he seems to think maybe it might be the knock sensor, can anyone help me, I have a long trip to make in a couple of days and need to figure this out, I don't want it to break done on my trip if I can't fix it, or does some one think it will be ok, it runs fine, no loose of power or anything. Thanks for any help.

 

blinking is bad, if it stays illuminated there is a problem but can be safely driven. when it blinks that means there is a problem that needs to be delt with soon or engine damage can result. What were the code or codes pulled from it?

 

Lukemoore, Thanks for the info, I'm not sure what the number codes are but I remember before the tune up my mechanic said there was a missfire code and something else. I am going to take it to a auto store and have the codes checked and I will get back to you with them and see what you think.

 

When the light is flashing it is misfiring while it flashes. I have never seen a knock sensor cause this or even had to replace one on a Chevy. I do performance testing and check engine lights almost everyday, I get all the crap that has been to multiple shops and been repeatedly misdiagnosed. www.goss-garage.com. Get the codes and I will see if I can help you.

 

I just went to the parts store and used their code reader and the only code that came up was P0300 random misfire. I had a all around tune up so new plugs wires etc, It was doing the same thing before the tune up and still doing it. Someone told me it could be the crank sensor, could that be it.

 

I would not take it on a long trip with it blinking like that, I hope you figure out the problem asap.

 

When everything is proved good, ignition parts, fuel pressure and volume, injectors and vac leaks. GM has a bulletin to shim the crank sensor. When the engine gets older the plastic timing cover gets warped which changes the air gap on the crank sensor causing a po300. The part number for the shim is 12565102. Try one first you can use up to 2. They are avalible through the dealer.

 

Thanks for all your help, I have ordered the shimmes to see if that works, its going to be a cheap fix if that is it. Now I just need help finding the crank sensor.

 

Lat under the front of the engine. Just behind the crank pulley is the crank sensor, in the timing cover. It is held in buy a single 10mm head bolt ( it maybe a 8mm). Remove the bolt pull out the sensor put the shims on it and reinstall it. The entire process should take around 5 minutes.

 

MDTahoe, Thanks for all your help, I ordered the parts from the dealer, they will be here in a week. If this works this will be a cheap fix, $5.74. As soon as I get the parts and put them in I will let you know if it works.