Hey Im new to the forum. ASE master tech for quite a few years. Picked up an 02 2500 4x4 with the 5.9 gas motor which runs very strong and quiet. 160k miles. Bought truck for cheap because PO thought it needed a trans. which it still might. Did not want to go into OD so I hooked my scanner up to it. Using matco determinator with latest software saw that governor pressure sensor stayed at .45v no matter what speed when I thought it was suppose to increase. Also GP solenoid not at target value. I put in mopar GP sensor and solenoid with new filter and +4. Test drive 5 miles shifts are very smooth, no problems. GP solenoid values are now on target but pressure sensor still sitting at .45v no matter what speed. Ran good so figured I would just drive it. Next day on highway i get on it then come to a stop. OD off light comes on. Turn truck off started back up and no lights. Drove home fairly easy and shifting through all gears normally. Yesterday light came on again and when this happens its when Im coming to a stop I feel a slight shudder and light pops. Never comes on under acceleration. Scanned ECM and find pressure sensor volts still locked at .45v and a code p1740 is set. Now my ?'s are should I address that locked .45v governor pressure sensor first? Would that cause issues? Or should I clean and or replace the TCC and OD solenoids because GP solenoid screens were clogged 100%. Someone must have forgot magnet in pan served a purpose, was missing. Sorry for the essay.

 

But, its a good read.

GP solenoid clogging up is pretty common. The Transducer staying at .45 is indeed a problem, and you need to address that.

Does your trans temp light also come on when when the O/D light does?

There is a check valve in the trans cooler line going to the radiator. They like to clog up with the same crap you found in the GP solenoid, so you get zero fluid flow thru it. Take off that section of hose, have a look, should be obvious which it is, goes to the lower radiator fitting. there are also a couple walkthrus in the faq section for replacing it with off the shelf parts. I just used a section of hose, and a couple clamps.

That valve is one of the (many) reasons for failure on these transmissions, it clogs, the trans gets hot, and burn itself up.

Welcome to DF. We are happy to have you here.

 

Hey thanks for the quick reply. I will look into checking the valve in the cooler line like you are saying. Just OD off light, temp. light has never come on. Ok so from what you are saying it sounds like the transducer reading is important for operation. Two mopar transducers in a row stuck at .45v no matter what speed. Im stumped on that. Ground is probably good because temp. seems accurate and rear 02 sensor is reading properly. Wouldnt there have to be fluid flow in there for the trans. to shift at all? Even if TC, fluid pump etc. were worn that sensor should at least rise some wouldnt you think?

 

Two other sensors had the same problem? That IS odd..... Can you read duty cycle on the GP solenoid? If you can, watch that for a bit, and see what it is doing. .45 volts sounds like minimum pressure to me.... which should give premature shifts and such. The fact that it isn't really is a head scratcher.

I am going to guess that there is some manner of bypass on the cooler lines, so if they do stop flowing, the trans will still work. (and unfortunately, burn itself up.)

 

I was thinking the same thing about the bypass. Yes i can read duty cycle. Thats a whole seperate reading. GP sensor has its own voltage and I think its suppose to rise with vehicle speed. Since its stuck and gp duty cycle rises as well as other numbers im thinking ECM. Another thing I noticed when scanning is gear reading is all over the place. Just changing constantly even in park from neutral to park to invalid to 2nd gear to 4th even when at a stop.

 

Gp pressure should be 1psi per 1 mph when in 3rd gear (1:1 ratio) and no load on the engine ( read as driving flat, just enough throttle to maintain speed). I don't know exactly what that corresponds to in voltage, but .45 v sure sounds like the zero pressure idle reference.


I'd say that you are dealing with either a wiring issue, or there's a blockage in the throttle body causing a no read issue on the gp sensor.

 

What confuses me though, is the trans shifts good, and GP duty cycle changes...... Now, with a fixed value for the pressure sensor, one would think that something wasn't quite right, and I would wonder what data the pcm is using to modulate the GP solenoid, and why it isn't whining about the fixed voltage, when it is obviously doing the solenoid shuffle.......

I would almost be tempted to plug in a different scanner, and see if you get the same results.

 

I'm going to scan another Chrysler truck trans. Today and see if I get readings. Gp is shuffling like its suppose to but voltage sits at .45 and gear selection in scanner is all over the place. Sitting still goes from third to neutral to park to first never stays at the correct gear.??? Sensor?

 

There should be a neutral safety switch near the shift linkage, I don't recall if it is internal, or external.

it could also be just a wiring problem......

 

I geuss wiring problem would be more likely because it varies all over the place. An off on type switch generally wouldn't do that.