01 Dakota Code Problems

Seriously needing help from anyone willing to give it to me... Truck basically shutdown, had the codes ran, and of course the dealership is going to tell me I need a new transmission. Codes were p0442 which is evap leak and p0445 another evap leak, but then i got a code p1790 and p0734. Anybody know what is really going on? And do I really need new transmission or are they just trying to make me buy it anyway...

desperate

p-0442 (most of the times it's a loose gas cap, if not it needs replacing.)
p-0734 (Gear 4 Incorrect ratio) How's the tranny shifting??
p-1790 (TP (Electric) Circuit Malfunction)

Most likely it's a couple of shot sensors on the tranny, (my guess)

Disconnect the battery "-" cable, then turn the key in the ignition like your starting the truck hold 15-25sec.
Then turn key back off. Hook up the battery go for a drive and see if the codes return. This is the way of resetting the computer and codes.

What year/model is this on?

No...dealerships don't make you buy anything...but we have to go by DC's rules on warranty. If the truck has the extended powertrain warranty (either from DC or aftermarket)...you should be covered (deductibles may apply)

P0442 is more than likely the gas cap gone bad
P0445 - Check the lines to the purge solenoid...that's a Purge Solenoid Short code

The other two codes are definitely transmission related but resetting the codes via the battery also clears other information (such as OBD2 Monitors and Freeze Frame information that can be used to diagnose the transmission or other problems).

p-0442 (most of the times it's a loose gas cap, if not it needs replacing.)

I had that same code, Pulled the rubber gasket off of the gas cap, soaked it in some Armor all to soften it a bit and then made sure that it was dry and clean before replacing it. Worked like a charm.

About a week later I got the same code, gas cap gasket was fine. Turns out that there was a crack in the Evap hose right by the testing plug, replacing the cracked section fixed the problem!

P0442 and P0456 can both be caused by the gas cap (and yes...a small leak in the EVAP hose). Best bet is to check for any rust or gas in the center hole of the gas cap. If there is...replace it (cleaning won't work). If not...check all of the vacuum lines under the vehicle as well as under the hood.

For the evap code,use a smoke machine and they do work.You can find the evap leak real easy,the smoke comes out and there is the evap leak

Sounds like a slippage problem. the first and cheapest thing that I would try is a fluid flush/filter change.

P1790 - FAULT IMMEDIATELY AFTER SHIFT

When Monitored and Set Condition: P1790 - FAULT IMMEDIATELY AFTER SHIFT
When Monitored: After a speed ratio error is stored.
Set Condition: This code is set if the associated speed ratio code is stored within 1.3 seconds after a shift.

POSSIBLE CAUSES:
FAULT AFTER SHIFT


P0734 - GEAR RATIO ERROR IN 4TH

When Monitored and Set Condition: P0734 - GEAR RATIO ERROR IN 4TH
When Monitored: The transmission gear ratio is monitored continuously while the transmission is in gear.
Set Condition: If the ratio of the Input RPM to the Output RPM does not match the current gear ratio.

POSSIBLE CAUSES:
RELATED DTC'S PRESENT
RELATED PRESSURE SWITCH DTC'S PRESENT
TRANSMISSION INTERNAL PROBLEM