If the code has an H then it is a History code :thumbsup:

 

air bubble,bad sensor. they can be tricky on bleeding.my books arent close by so i dont know where that sensor is.where there any elec. conectors on tank ? if not sensor is in side of rad.

 

My mother's '99 threw a low coolant message one time, then it never came back. The sensor can do that sometimes. Clear the code and see if it comes back.

To bleed the system do the following:

1. Remove radiator tank cap
2. Start the car and let idle for 1 minute
3. Install radiator tank cap
4. Rev the car to 3000 rpms and hold for 30 seconds, then back to idle for 30 seconds, then back to 3000 rpms etc. Do this until the coolant temperature reaches 210 degrees to ensure the t-stat has fully opened.
5. Shut car off
6. Slowly remove radiator tank cap allowing pressure to hiss out first
7. Start car and let car idle for 1 minute
8. Replace cap and do the reve deel all over again... you do the cycle 3 times per the GM service manual.

 

You probably recieved the wrong model surge tank. There is a small difference from C5 model years. The early 98 - 99 cars had a different style level switch built into the coolant tank than 00 - later years. It will plug in the same way but you will get a low coolant level message. I found this out when I purchased a painted coolant tank and the painter who also supplied the new coolant tank didn't realize this and sent me a later model style. After I had it installed I also kept getting a low coolant code and the coolant was full. After thinking the tank was defective, I spoke with the person who I had purchased the painted coolant tank and after some research on his part he discovered the model year difference. Mine just happened to be the first 1999 car he had painted one for. After he sent me the correct style all was fine. Any dealer parts department should be able to find both variations and get you the proper model for your 99 model year. The only difference between tanks of different years is the way the level switch senses coolant level. I don't recall the exact part number for a 99 sorry.

 

wow that was great info.its ashame that sometimes people wont come back with a thanks or the very least that they fixed it.its not like we are gonna charge them,then again maybe be we should,from now on all correct advise is one :thank you,wrong advise :thanks but no thanks,bad advise:i,m coming for ya. just a thought. oh yeah,thank you

 

The sensor is a floating magnet so if tank is off level a bit that would be the cause.
Also could be during shipment the magnet got wedged and is not floating.

Loosen the tank and have someone watch the dash, lift the tank one way or another to change the tilt and see if all it needs is a washer at one mounting end to level the tank to raise that corner.

Of course make sure the male pins of connector are not bent or not fully seated.