Have a truck I have a plow on, and been using it in my yard for a year until I just today put it on the road. Now I have noticed a transmission issue.
Drove it today for the first time any distance since I owned it
After driving about 15 kms I was at cruising speed in O/D, and come on a hill, it downshifted hard, I then let off and it shifted back into O/D, then back on and it downshifted hard again, but this time it threw a code, p0700, and wouldn't go back into O/D again
After driving it back home I have found some quirks that suggest it's something electronic, maby?
If I turn the truck off then back on O/D works again until it downshifts hard twice, then no more O/D. Also when the truck is in this mode with no O/D, when sitting parked it shifts hard into R and D. But when I turn the truck off, then back on, back to shifting smooth again, until I get it to speed and it downshifts hard again.
Also when upshifting, If I accelerate agressivly, when going from (I think) 2nd-3rd the truck shudders at all times.
There are a few electrical issues with this truck that I don't know if it couuld be related to any or all.
Power locks only work with key, and not from door switches, I took the panel off and the switch isn't getting the 12v it needs, checked all fuses are good.
Right turn signal flashes fast, even though both bulbs are good, but not the drivers. Had a bad bulb on drivers side and it still flashed normal speed.
Blower stuck in defrost (blowing at the windshield)

Any suggestions appreciated
thanks

 

Hi Marc and welcome to the forum.

On the turn signals, there are 2 bulbs in the front on each side. Make sure they both work.

On the HVAC, if you only get defrost it sounds like you are not getting vacuum to the control head or the head is defective. Under the hood, near the power brake booster, you'll see a small plastic vacuum line going into a tee. There should be a check valve there. If it failed shut, no vacuum to the controls, you're stuck in defrost. You can also pull the vacuum lines at the control head to check for vacuum.

The transmission: P0700 indicates a diagnostic code has been stored in the TCM. Most code readers won't read these codes, the dealer can, or some good transmission shops. Getting it read might be the easiest and cheapest way of finding out what is happening. You might start off with a fluid/filter change just in case but it may not help.

The door locks, double check fuse 13 in the junction block, by the drivers door. You are checking pin 1, on the connector at the drivers door switch? It's a 16 gauge red wire. The weak point in the system is usually the drivers door switch. The good news is that if the key switch works the CTM is responding.

Lots to check. Good luck.

 

Thanks for the reply. I search this forum all the time and find answers without having to post anything, so this time I could not find anything with the same issues I'm having.
I will haveto take it to a dealer or tranny shop to see what the issues are. On thinking about it later, I realized It shudders when upshifting into 3rd, and gives an almost "bang" when downshifting into 3rd.. I'm now thinking It maby something mechanical that the electronics are putting it into a protection mode when it senses the hard downshift.
I previously got the wiring diagram for the door locks.. I got the locks unlocking by putting 12v on the pink/violet wire on the connector behind the door panel, but by applying 12v to the lock pin (orange/violet wire) the doors would not lock.. Where I measured and found no 12v where there was supposed to be was on the red wire in that connector. fuses I've tripple checked..