Blaze,

Was you high temps fluctuating rapidly or moving steadily up to the high temps and back down? My temps are jumping erractically from normal to very hot to normal again.

Cleaning the radiator would be easy and cheap. In fact, I probably would have wiser to do that before putting the new pump and stat on.

 

I had a similar problem. My temps where climbing to 255 while sitting at lights/stop signs, but would fall back down to 200/190 while driving. I replaced my water pump and it's all good now.

 

My temps aren't climbing. They are jumping - directly from 190 to 240+ with no degrees in between.

 

After driving the car some more and getting the xxx DIC temp, I have these codes:

10 PCM
P1114 H ECT Sensor Circuit Intermittent Low Voltage
P1258 H Engine Coolant Over Temperature-Fuel Disabled

B0 RFA
U1096 H Loss of Communication with IPC
U1064 H Loss of Communication with BCM
U1016 H Loss of Communication with PCM

I am getting my code definitions from this page:

http://www.stengel.net/diccodes.htm

I don't know what B0-RFA - Remote Function Actuation is refering to.

There seems to be a loose of communication between the IPC the BCM and PCM, which may or may not be related to the Engine Coolant Temperature problem.

I dont have a shop manual. The IPC is the Instrument Panel Cluster correct? and the BCM is the Body Control Module which is the box under the passager side floor board correct? And the PCM is the Power Control Module under the battery correct? There must be a bad connection some where in that hi-tech electronic snake pit.

 

bump... need info...

 

Yes you are correct and RFA is the module for your tire pressure monitors and the key fobs.

 

In a 99 FRC we just put in a new water pump, new radiator, new hoses, and a few other items not related to the water system (e.g., transmission). Car ran fine for about 100 miles or so - but the oil cooler block leaked again so Jake had to go in and fix that. When we cranked it back up a day or so later the water temp was normal for about 5 seconds then spiked to 260 and the DIC said coolant overtemp.

No codes are on the PCM. But after checking connections to the sensor under the alternator it still did it (260 Spike). Jake ran the lines again and checked it with the key on and the engine off - everything worked! Cranked it and everything looks good.

Is there a another water temp sensor anywhere?

The local dealre does not have a sensor - any ideas where we can pick one up between Augusta GA and Danville, VA?

thanks...

 

I had the exactly same problem with my 2001 vert with supercharger. Today I installed 160 thermostat and add some water wetter to the water. The main issue was the thermostat. After the installation, I checked the old thermostat, and there was a lot of scratches. And the mechanic told me that my old thermostat was bad. Now my car is running around 185~195 range in coolant with the outside temp about 85. Before the installation, the range was about 225~240 and sometimes it was hitting 260. I definately recommand to change the thermostat.

 

Thanks for the help. I suspected that "radio" had something to do with something wireless, but the tire pressure monitors never give any problem and the keyless entry works fine. Yet I'm getting RFA communication codes.

I pulled the wheel well liner out and took a look at the computer under the battery. It had some external road corrision from winter driving in OH, but when I pulled the computer plugs out they looked new and shiny on the inside. I can't find any connections or wires that look suspicious.

 

Good question. Does the PCM and the DIC use the same sensor? I just assumed that they did. From some quick internet searches, apparently the LT1/LT4 used two different sensors.

 

There is one temp sensor in the left cylinder head that feeds info to the PCM and then the PCM feeds info to the IPC.

As far as throwing codes for the RFA module but not having problems with the tire pressure sensors or the Key fobs, what your having problems with is communication between the modules which is totally different. The picture that Bill showed with the plug in the door jamb showed a bare wire with a clear plastic cover over it, this is the databus that connects the modules, you'll find a few of these throughout the car and if one of them shorts out funky things happen.

Thats why I said you needed to remove the accordians and put some electrical tape around that wire to keep it from shorting and also see if that fixes your comm problems.

 

YEP,, ,,,that door harness issue will surely cause whackey electrical issues!! I think I recommended that you check that in a PM I sent you.

BC

 

After laying on of hands and the appropriate blood sacrifice the sensor seems to be all better now

It will get a good ops test at VIR all this next week

 

First, the Service Manual says to DELETE any Uxxxx codes posted in modules. There are no diagnostics for them. The only time they are useful is if you are getting a NO COMM message for a module when querying DTC data from the system.

The computers in the car are interconnected by a "Local Area Network" type arrangement. There is a lot of data being moved around, and when a computer wants to send a message and the data bus is busy, it will post a Uxxxx code. Any Corvette will show some in various modules at any point in time. Just delete them.

As previosly answered, there is only one coolant temp sensor, which is wired to the PCM. The PCM then transmits that data on the LAN so that, for example, the IPC can display it both on the gauge and on the DIC. The PCM puts out a lot of data on the bus, engine RPM, road speed, oil/water temp, etc. Much of this is used by the IPC, but other modules such as the SDM (AIr bag module) also collect some of this data. That's why the bus is so busy, many modules are sending and receiving data almost simultaneously.

HTH

 

EXCELLENT explaniation!!!!!!!

BC

 

I am having the same problem. The temp gauge will go from nornal to pinned and then back to normal in less than a minute. It would do this about oce a week. Then one day it did this twice. The third time the gauge did not return to normal and I lost power. I looked under the hood and it was truly overheating. The car is in the shop now. After reading this thread I fear they will not figure it out. Did you ever resolve this issue?

 

Add me to the list of people with this problem. Mine seems to be a bit different though. It just started happening today. Heres what I have done to my car in the past couple weeks:
installed shorty headers (broke coolant temp sensor in the progress)
installed new plugs and wires
oil change with royal purple 5w-30
added RP purple ice to coolant
replaced coolant temp sensor
accidently left coolant cap loose and boiled some coolant off (shut w/in 5 min, as soon as I could pull over)

Symptoms:
temp quickly rises to 240ish shortly after starting
temp seems to stabilize around 239F while driving ~50mph
looked under hood and only passenger side fan running at 251F (drivers side dead)
all fuses are good and all relays pushed in all the way
temp seems to track normally while increasing (not making huge jumps in temp)
temp sometimes increases to ~250F at stoplights
little bit of junk in front of radiator, but not a lot (buildup at top inch or so)

First, I want to figure out why my fan isn't turning on. If that doen't fix my problem, I'm thinking its probably a bad t-stat or maybe even water pump. One other thing I thought of was that since I left the coolant cap unscrewed and the coolant was at atmospheric pressure, maybe some boiled inside the head by the temp sensor and there is a vapor pocket stuck in there. I would appreciate any help/suggestions.

 

My issue is that both fans run, just don't think that they are turning on high. Without AC on the car does not get much higher than 200-210 max...usually 190ish. When moving with the AC on stays right in the same area from 190-210 max. sit still at a light and its starts to slowly climb...and will keep going till AC is switched off.

Raditor is flush, good mix, t-stat looks like its working...temp seems even throughout top of radiator...

any suggestions?

 

i'm having the same problem..new pump,new thermostat.new coolant..35,000 mi car..i was waiting to see if someone could tell me where the temp sensors are

 

i just went out and wiggled the temp sensor plug....now the car shows 215-220...hhmmm...i'll go test drive.....i already did the pump and thermo....133.98 pump...19.99 thermo...advance auto parts