2005 automatic starting off in 3rd! Any Ideas?

[Blacksdieselhp]

I have a 2005 4wd 2500 with automatic. It is bone stock. It has 101k miles on it. i got it in Florida and drove it home to north ga with no problems. Then the other night, I noticed when taking off, it wasn't in 1st gear. I stopped and started off several times. I thought it was taking off in 2nd, but its 3rd. It shifts one time, then locks up. I am thinking it is something electrical. I have heard that the ground in the pcm can go bad and cause this. Any ideas of what it may be? It was raining the night it started doing this. It just occured to me that maybe the connection got some water in it. Guess I'll check that tomorrow.

 

[OPoole]

Check the hardness on driver side of trans. going to VB.

 

[lgjohnson]

I had the same problem on my 03. The first time, it was water/dirt on the connectors going to the PCM. The 2nd time, it was the PCM itself. What was happening was the ground for the transmission relay coil wasn't being made up by the PCM and not energizing the electronics in the transmission.

To make sure it was the PCM and not something else, I replaced the governor solenoid, pressure sensor and gear indicator sensor (with close to 100,000 on my truck, they probably needed it anyway as it sure does shift a lot better now).

Do the indicator lights for R, D, 2 and 1 positions on the dash all work when the engine is running?

In my case, it was the PCM, but I didn't replace it. Instead I ran the relay coil to a separate ground and it works just fine. I'll probably eventually change the PCM.

Are you getting any diagnostic codes? Mine was not throwing any at all.

 

[Blacksdieselhp]

Thanks guys. Which wire did you run to ground for the relay coil? What color was the wire? I am gonna put new gov pressure sol and sensor and see what happens. If that doesn't do it, I guess I'll ground the relay coil like you said. Thanks

 

[WUnderwood]

when mine did it, the culprit was the gov pressure solenoid

 

[zstroken]

transmission is in limp mode, check for codes.

 

[Blacksdieselhp]

No codes. Guess I'll replace the gov pressure solenoid and sensor and see what happens. This is my wifes truck. I'd hate for the transmission to be bad and have to put a full built Georend transmission it :-laf

 

[lgjohnson]

The gov. sol would probably toss a code if it was bad, but with that many miles, it sure wouldn't hurt to change it. Do both the solenoid and the pressure sensor since they are right there together. They are separate part#s and the solenoid ain't exactly "cheap"...
A service manual would help with the following:
Anyway, my truck is a 2003 so I'm not sure it is EXACTLY the same as yours, but IF it is, you could start by checking fuse #5 and #50 to make sure that its not just a blown fuse. #50 feeds the transmission relay coil and is 10A. #5 is 40A and actually feeds the transmission. Even if they look ok, I would check with an ohm meter to make sure.
IF the fuses are ok, Relay #59 is the transmission relay. You will see several relays that are the same part#... such as the fog light relay. I swapped them just to make sure I didn't have a bad relay. Pull it out and check for voltage at terminal #30 and it should have voltage even when the key is off (terminal #s are on the bottom of the relay next to its pins, but you have think upside down... . :-laf). Then check for voltage at terminal #86 (coil +voltage feed). There should be no voltage except when the key is in the "run" position. Also as a check, you can make a small temporary wire jumper, with the relay pulled out; jump from #30 to #87 terminals and see if the transmission "comes back to life". IF it does, check for continuity between ground and #85. Since #85 is the relay coil's ground that runs back to the PCM, it should be around 65 ohms or less. IF it isn't, its probably open..... like mine :{. The wire that runs to the PCM is the #18 gauge pink wire going to terminal #30 on Connector C2 (white one in the middle between black and gray) on the PCM. I undid the harness a little bit, snipped the pink wire and ran a jumper from the pass. side battery ground to the side going back to the relay. I just taped off the wire that was left going to PCM C2. Truck has been running fine.
IF you have access to the service manual, check out page# 8W-31-16 for the schematic. All of this is ASSUMING your truck is the same as mine. IF not, pop the cover off your relay/fuse box and inside the top cover, it will list the fuses and relays. Find the transmission fuses mentioned above along with the transmission control relay and do the jumper thingy to see if it comes back.
Hope this helps.
BTW, I changed my gov. solenoid, pressure sensor and gear position sensor and when the transmission came back to life, it shifted better than it did when it was new... . lost alot of the harsh shifting under load... . and oh yeah, I HATE electronics in a transmission.....