jlbonnie2000

I have three 2002 Camaro's with V6 motor. All three have exactly the same problem. Since my Camaros do this, I bet many more do also. Here is my problem...

When I first start the motor, the cooling fans come on (all 3 cars). When this happens, I know the temp gauge will stay at the lowest setting (dead) and not come up.

I eventually get the "Check Engine" lite on (all 3 Camaros). The fault is PO 128 (all 3 Camaros). It takes a while before this lite comes on. I can clear it out with my resetter tool, but it will come back on.

None of my Camaros have an engine overheating or cooling problem. They all run fine. I have opened the radiator cap on all three at different times after driving and measured the water temp. It's always within spec.

I have replaced the engine temp sending unit on one Camaro. This did not fix the problem.

I have removed the connector to the computer on all 3 cars, cleaned the contacts with elecrtical contact cleaner, and re-connected. This had no effect on fixing my problem.

This dead temp gauge is intermintent (all 3 Camaros). Sometimes the gauge works fine and sometimes not. I can always tell when the gauge will NOT work when I crank the engine and then the cooling fans come on right away. So, it is not a bad or faulty gauge.

I don't know what is causing this issue. Since I have the exact same problem on 3 seperate Camaros, I know it's NOT the sending unit and NOT a bad connection. I am at a loss as to what it can be.

I need someone to reply who can duplicate this exact same problem and has some answers on how it can be troubleshot.

John

Freakv6

I have this exact issue in my 01 v6. Its due to the car not warming up quick enough. Do you still have the stock thermostat in them? Mine is due to have an aftermarket one that doesnt allow it to warm up quickly enough.

jlbonnie2000

I think the symptom of the dead temp guage has two causes. In my case, it was the temp sending unit. Since I had 3 Camaros acting the same way, I didn't think I had a normal or hardware issue.

I went to AutoZone and purchased a sending unit. That fixed one guage on one Camaro. I bought a second unit and I will install it in the other Camaro. These untis were $10 each, so pretty inexpensive fix.

Im my case, as soon as I start the engine, the cooling fans come on. I read where if no feedback comes from the sending unit, the computer assumes an over-heat condition and turns on the fans. Right away! No delay on startup.

In the case of a weak or slow thermostat, does your cooling fans start immediately after starting the engine? Like in less than 5 seconds?? Do you get the PO code 128?? All 3 of my Camaros get this same code.

My wife is presently driving her 2002 in another state. The fans are on and the "Check Engine" lite is constantly on. She emailed last night and said that yesterday, the temp guage popped back to life and the "Check Engine" lite went off as did the cooling fans. I will install her new sending unit when she returns home.

Freakv6

My fans will start upon initial startup, but only if the gauge was at the "0" reading the last time the car was shut off, and the PO128 was already set. This usually happens for the first time when it is cooler outside and i run the car at highway cruising speeds (after a short time, the gauge will fall to 0 and my light will come on). I think mine is to do with the thermostat itself. Since both are cheap to replace, i will eventually try the thermo first, and then the sending unit if that doesn't help. Where is the sending unit located?

transamtom

Either the coolant/temp sensor is bad or your coolant system is not bled properly and there is air in it.

The same thing happened to mine.

The temp gauge and coolant system sensors are all in one unit on the V6.

Its located under the Throttle Body,remove the bellows to get a better look.

jlbonnie2000

Again, with (3) 2002 Camaros all with V6 and all having this same dead temp gauge, I replaced the sending unit on one a few days ago. I replaced the second one last night.

This morning, I was still puzzled as to why 3 cars have the exact same problem? I then looked at the sending unit I had replaced. It has a brass body. On one corner, it is worn very shiny like something was rubbing on it.

I went to the garage and looked at the unit on my Camaro there. I see the serpentine belt is about a half inch under this sending unit. This sending unit is also in the center of the longest run of the serpentine belt between to pulleys.

The longer the serpentine run between two pulleys, the more it vibrates. When running the motor, I see the serpentine belt bouncing noticeable under this unit.

I have long thought this is a design issue with the sending unit. I can see this unit was mounted too close to the vibrating serpentine belt. I think the belt smacks this unit millions of times strong enough to rub a flat spot on the sending unit. I can very easily see this as slowly causing the sending unit to fail from this added vibration.

As long as this is an known issue, it is very easy to cure. For $10 and less than 5 minutes time, a sending unit can be replaced.

I bet if every 3800 V6 owner looks at his sending unit, he will see this shiny area where the belt rubs on it.

As an engineer, I can see where this went un-noticed at the development factory. However, there should have been attention to this issue thru common failuers to bring out some kind of service bulletin.

It's past history now, but by simply drilling the mounting hole a little to the side to avid contact between the sending unit and the belt was very easy fix to have done.

Just my observations........John

Freakv6

Makes sense to me. When you were refering to it as a sending unit, i was thinking you were talking about something other then the temp sensor itself. (i thought it may be seperate). I will just pick up the new sensor and give it a try. There is no issue with air in the lines, so this just about has to be my problem. Thanks again for the info.

Need4Camaro

The problem here is NOT the temperature gauge sending unit... you have a bad thermostat... here's whats really happening...

Your PCM is detecting that its taking longer than normal for your temperature to rise to normal operation temperatures, its taking longer cuzz the thermo is stuck open... The PCM becomes afraid that the temperature sending unit could be faulty and the motor COULD be much hotter than the gauge reads, immediately throws a code (triggering the SES) and disables the temperature sending unit, which kills the gauge, and automatically turns the fans on to prevent the possibility of overheating the engine since it no longer knows how hot the engine will be running... it's a failsafe feature...not a problem

To fix this, replace the thermostats on your Camaro's.

transamtom

I have a brand new 180 thermostat,I tested it before it went in.

If the temp sensor see's a reading thats not in its normal range it will do the same thing,turn the fans on.

This can happen if the system is not purged of air properly.

Freakv6

I replaced my temp sensor yesterday, but no dice on it fixing the issue. This really just leaves my thermo as the culprit, my next free off day i will try that out.

uminert

I think the problem is a loose wire or faulty gauge as I have the same problem on my 2002 Firebird with the 3800. For a long while, the gauge was not registering and then when I'd drive over bumps, it would come back and start registering. After doing this over the last 6 years or so, it has finally stopped registering and the cooling fans run continuously.

Injuneer

Have you scanned it for codes? If I am reading the engine control and dash diagrams correctly in the 2000 factory manual (the only one I have, but hard to believe much changed between 2000 - 2002), the ECT sensor under the throttle body is a 2-wire sensor, connected directly to the PCM. The PCM in turn streams various operating data to a solid state module in the dash, that controls the tach, coolant gauge and fuel level gauge.

The 2000 manual does not list P0128 as applicable to the 3.8L V6, but shows P0117, P0118 and P0125 related to problems with the ECT sensor. But the GM service website DTC listing for 2002 F-Body 3.8L V6 does show P0128 - Thermostat/ECT Rationality:

https://service.gm.com/gmspo/mode6/p.../2002file4.pdf

Have you scanned the PCM for codes?

An open circuit for the ECT sensor means infinite resistance, and that corresponds to a low temp indication, consistent with your gauge staying at the bottom of the range. That could set at least two of the codes above.

Need4Camaro

Very slim chance that its an air problem. The OP is stating the the gauge is dead from the moment he starts the car. Even if there is air in the system there will be enough to give him an engine coolant reading during startup and at least until the car reaches operating temperature and then the PCM will decide that the reading is not within range then kill the gauge and throw the fans on but the OP isn't even getting to that point, its going failsafe as soon as he cranks it.

This is a VERY COMMON PROBLEM with the 3.8 V6's. I've ran into it myself. TRUST ME, replace the thermostat and the issue will likely be resolved.

Edit: Whoops, just read the date on these, somehow this popped up on my recent post list...oh well.