While the wife was driving her excursion I was watching some sensors using my AE and noticed that the coolant temperature input was 302`,but showed normal on the dash, oil temp was 165. After a while it would start to bounce around 32, 83, 120 just all over the place. When we got home it was stuck at 302 again, I had another sensor laying around and plugged it in but nothing changed? With the sensor unplugged the gauge would read cold but the AE would still show 302 degrees, plugged in it showed normal temp on the gauge. Any ideas?

 

165 sounds a little cool for oil IMO, I usually ran around 200 with the last truck. Don't have that gauge on this one yet. Normally EOT should be within +15 of ECT once everything is fully up to temp. If it's higher than that, it is pointing towards the oil cooler not working as it should.

I was going to suggest a short or broken wire, but since the gauge on the dash changes depending on if it's plugged in or not, that shouldn't be it. I was also going to see if you weren't seeing *C by mistake, but the numbers don't work out. Is it possible your Tstat is stuck closed and you're getting actual temps with AE, but the ECM is averaging out and seeing everything as normal? If so that could be a little bit of an issue...

Then again, why is AE still reading 302 with the sensor unplugged? Sorry i'm doing a lot of thinking out loud and not being much help...

 

I didn't think coolant temp was sent through the OBDII port.

At least I can't get it to display on my ScanguageII.

 

If I remember correctly, a 50/50 mixture @ 15 psi gives a boiling point of 265 degrees F...so, the OP isn't seeing 302 F unless his engine is seriously overheated (think steam...lots of steam). I'm betting the AE is getting a bogus reading somehow.

Does the PCM have an overheat strategy built into it, i.e. ECT > say 265 F, defuel the truck? I don't think so, but not certain. So, if I am correct that the PCM doesn't care about "overheating" data, a bogus reading wouldn't cause any driveability issues. Of more concern to me is the 165 F reading of the EOT. As Jeff said, that is too cool for a fully warmed up engine.

Edit: volthause probably has nailed the issue.

SECOND EDIT: I just found this post:

"I wrote to AE support about this issue. They confirmed that the pinout is there and AE sees it but the 7.3 application does not use this pinout so it floats - the result is that we see bogus information. Just ignore it, it's a result of Ford using the same hardware for multiple applications.

So now we have our answer - just ignore this information. Wish I had known this before - I momentarily panicked when I saw my coolant temp at 280°F!"

 

Don't know for sure, but the SG user manual shows FWT (water temperature). I'm guessing that's standard for all vehicles. Also, if it didn't show it, shouldn't AE not have the option to read it?

EDIT: Neal has it pegged I guess, but I don't know why AE wouldn't be able to read it correctly. They should have that figured out...

 

Jeff, doesn't the coolant sensor only feed info to the dash gauge? What does the PCM use ECT for that EOT couldn't act as a surrogate?

EDIT: I just checked the 1999 PC/ED Manual and it does not show any input to the PCM for ECT.

 

Just found this post by Woodnthings:

My knowledge is expanded everyday.

 

You and me both ! So to the OP, ignore all ECT readings on AE (if it is an auto tranny...which I believe yours is), they are bogus on your truck.

 

I guess that is why AE has the capability to see it. Manual trucks would likely get a valid reading through AE, while auto will not...

A better question is this: Why do we have an ECT gauge on the dash rather than EOT? I know that's standard for what drivers want to see, and we all go above and beyond to monitor other systems, but if it's not even important enough for the ECM to see, why do we need to see it?

EDIT: It's a rhetorical question really.

 

Does anyone know if this is just an issue with the AE or all scantools? So does the gauge cluster have an ecm?

 

By ECM, I mean the main computer module for the truck that controls everything. It seems as though the automatic trucks have coolant temp senders that bypass the ECM and go strait to the gauge itself. Apparently there are no way to read it without adding an A/M gauge.

 

Since the coolant temp sensor on an automatic bypasses the PCM and is wired directly to the instrumsnt gauge any scantool relying on the OBDII port will not see the actual coolant temp.

The gauge cluster does not have it's own ECM.

 

As PaysonPSD & others have stated, for auto trucks, all scan tools.

For auto trucks, since no ECT sensor is connected to the PCM, no scan tool that relies on reading OBDII data from the PCM in order to display ECT data will work.

The only solution is a standalone gauge ... or maybe if you could replicate the same ECT sensor data signal & connect it to the correct PCM pin used on manual trucks?

 

Kudos on the search function!