I removed the trans cooler from the 03 with the bad engine and what came out of it was black. I've never seen trans fluid look so black, there wasn't a hint of red in there. If it wasn't the viscosity of water I would have thought it was an oil cooler. Now I'm planning to bring the gearbox from the 04 along with the engine as a precautionary move; there was actually even a stored code in the 03 for 4th gear incorrect ratio (P0734). I'm not sure that's accurate or even relevant but the trans in the 04 has zero issues so I don't see the point in gambling on the 03 trans due to what came out of it.

So, my question is how does the 04 tell the ECU about trans temp? Both clusters have the over temp lamp but the 04 doesn't have the temp sender fitting in the bottom of the cooler. The 04 cooler is in much better condition than the 03, which doesn't appear to be leaking but has rotted fins, so I'm planning to bring that over as well. I don't want to confuse the ECU(s) when no trans temp is reported due to the absence of the sensor in the cooler. Is there a sensor in the 04 trans itself? The RAVE made no mention of that, the only reference to the trans temp I could find was this pic.

 

the d2 electrical library says that there are two sensors, one on the cooler and one on the transmission itself, and that both signals go to the same pin on the instrument pack. if an earth path is completed on that pin (i.e. by either sensor) then the lamp comes on. so i would think that you could simply not worry about the cooler sensor so long as the transmission sensor is there.

 

Ahhh, I didn't think to check there! Thanks much. I remember reading that if the ECU sees a large variance between the temp sensor in the radiator for the gauge (sort of), and the one in the intake mani for fuel mixture it will throw a code. I was afraid of this happening with the trans temp due to the dangling connector however as you pointed out this is just a simple earth switch and not a variable sensor so that shouldn't be an issue.

Is there any way to tell the location of these sensors or the header based on the nomenclature? I'm used to a master guide at the back of the ETM that lists where to find these things, but only from 80s cars with 30 or 40 different items/places and not the thousands that are on these trucks.

 

back to the electrical library....

c0293 is "behind lh side of fascia" and there's a photo showing what looks like the rat's nest of wiring under the steering column. the rave doesn't say much about the location of the sensor on the transmission but it should be pretty obvious once you get the whole assembly out. its wiring will presumably go into one of the plug assemblies.

 

Damn, so much to learn. I was looking at the 152 page ETM and not the more robust 705 page Electrical Library! Having just checked, working on this truck should be a walk in the park comparatively. There are clear color pics and everything. Here's what I'm used to working with for the last 25 years. You have to be part detective and part mind reader, and have a pretty good imagination. Luckily there are only a couple dozen different components... Thanks again mollusc.