2006 Chev Impala - Coolant Reading

[92zman]

We got a 2006 Impala in that the temp gauge is not reading and the display is saying then the motor is hot and then it is shuting off the a/c. But when i put the scannor on it it is showing what i think to be the right temp. After letting it run for a while it is about 200. The fans are running the whole time too like it is hot. All this starts when u start it. At frist it had done it a few times but now it is on all the time. I belive the pcm to be doing it. Cause the cluster dont run the fans. I did unpluge the sensor to check the pcm and it did go down to -40 like it should. Dont know if anyone has seen this. I look for two temp sensors but could not find one. the car has a 3.5L in it.

[ricmorin]

The IPC gets coolant temp info from the PCM via class 2 data line. Have you scanned the IPC? Any codes? What is the data PID for coolant temp when read from the IPC?

[92zman]

No codes in the IPC and the pcm had a P0128 Could not look at the temp from the ipc from the scannor.

[ricmorin]

That's pretty weird. Could it just be an intermittent sensor?

[ricmorin]

I found a TSB for intermittent PO128 that involves PCM reprogramming. Might be worth looking into. It takes 255 degrees to shut off the AC. PCM controls that directly, so I think the IPC issue is isolated if the gauge differs from the data pid.

HTH

[92zman]

yea if i read the temp with the scannor from the pcm it is good. like 200 to 205 is all i have seen out of it. No where close to 255. At frist it was doing it then stopping but now this is all that is does. Even when u start it fro the frist thing in the morning. And u have to keep in mind then the fans are running the whole time too. that is the weriod part is then i can read it with the scanor but the fans are on even with the a/c off and the gauge dont move and it is saying then it is over heating. If the fans where not running then i would say then the IPC is just bad. Customer just bought this thing and thought he got a good deal on it. started happening like 2 days after he got it. Now it is just all the time.

[ricmorin]

Just a thought here. Maybe it's the PID that's wrong. Have you used a temp gun near the sensor location to confirm the pid? Maybe it's really getting too warm and the gauge is indeed correct and it's the pcm output of the pid that's messed up. (never seen that but it must be possible)

[92zman]

yea i did when it said 165 i got a reading 162 on my gun.

[ricmorin]

Drat!

Well then, I suppose I'd try flashing the pcm for the known PO128 problem and see what happens. Can you flash in-house?

[steven kiser]

I find flashing in public areas is best...................

[92zman]

No we cant do it in house will have to take to dealer.. And when u go flashing stay where u are..lol