Hey all I have a good one for ya. For a while now my dakota's overdrive hasn't been engaging. I replaced the solenoids in the transmission thinking that would fix it, but that did nothing. I got my mechanic (who is also a good friend) to take a look at it and he took a scanner to it and said something was up with the PCM. He said for whatever reason the programming had buggered up, or so we thought, and was telling the transmission it consistently -40 celcius out. So we replaced all the sensors to no avail. He tried to reset the PCM but for whatever reason that would not do a thing. So we figured a new PCM would fix the problem. I went to the junkyard and got a pcm for my dakota for a $150. Hooked er all up and fired the truck up and went for a drive. Nothing, overdrive will still not engage. Is it possible the wiring harness is buggered up? Maybe a bad ground?

 

Does this PCM still see a -40 temp?.......One way of getting your bearings on a NO OD shift is to attach a pressure gauge to the trans on the right side to the 1/8 NPT fitting just in front of the extension housing...If there is NO pressure whatsoever when the 4th shift should occur, then it is valve body,solenoid or electrical...If there is low pressure then there is an hydraulic leak in the 4th clutch circuit..If there is full pressure ( around 60 psi or more), it is mechanical, such as 4th clutch set itself is not holding....

Brian

 

It can't be the valve body or solenoid, and as far as I can tell all the elctrical is good coming out of the transmission. I have to wait for my mechanic to bring the scanner back again so we can see what the PCM is saying. Ill ask him about the pressure gauge to and see if we can't read what it has to say. Thanks.

 

Had this problem in my 03, replaced tps and iac. Fixed the problem

 

Also look at your neutral safety switch readings...Its rare that the switch goes bad, but the insulator behind the switch breaks and will give an incorrect signal to pcm, causing NO OD shift...

Brian

 

@nickcornell- What is the TPS and IAC?
@bjr1a- What is the neutral safety switch and how do I get readings from it?

thx guys

 

The neutral safety switch keeps the engine from starting in any gear position other than park and neutral...It is located on the left side of transmission near the gear selector just above the pan rail...It has a 3 wire connector.....If the scan tool has the same reading in D as it does in Park/neutral, then there is your fault......There is an old school check but use EXTREME caution....Place gear selector in Park position and have someone hold the brake ( NEVER get under a running car without safety measures) and start engine, while engine is running, unplug the 3 wire neutral safety switch connector....now that the circuit is open, the trans will shift to OD if there is a problem in that circuit...

Brian

 

Idol air control and throttle position sensor, mine were throwing codes and then one day my od stopped working. Changed both, then it worked again. I tried everything before that.

 

Ahh OK I see. Now if I tried to start it in a gear other than park neutral and it wouldn't does that mean it is working?

The odd thing is no codes are being thrown. It starts up fine and no CEL ever comes on. Today it started doing things as well, at first it wouldn't start, then when I got it going it sputtered and idled at 1300 rpm/. I turned it off and restarted it and it did the same thing. I didn't have any other way to school so I took and luckily it went back to normal. Until I got to school. I went to go home and when I put it in reverse it died. I tried starting it in reverse to try Bjr1a's theory but no dice so I put it in park and restarted it. Put it in reverse and it died again. Tried a third time and it finally worked. Did manage to get home with no problems. Man this truck is gonna be the death of me.

 

This is an obvious place to start, but have you checked your transmission fluid level?