Transmission Codes P0731 and P1790 Dodge Stratus 1999
 

Hi all,

Decided to have my oil changed along with my transmission fluid flushed today and shortly after (about 30 mins) engine light and these two codes (P0731 and P1790) came up. My stratus also would not seem to go past around 30-40 mph and what I assume was 1st gear. Took it back to the shop and they ran those codes and tried to convince me it's electrical and it wasn't caused by them flushing the fluid, and they showed me the fluid level after messing with it for some time.

As I drove away from the shop... it started shifting properly again. I didn't try to go past 50 mph, though. But it has been shifting rough lately. Engine light is still on but I only drove for another 5 minutes after taking it back to the shop.

A few years ago my car wouldn't shift out of 1st and I had to replace some type of sensor and it fixed the problem.

Any idea what might be going on?

p0731 Gear Ratio Error in First
p1790 Fault immediately after A shift

First, when you say "flushed" was it some type of "power flush"? Those things, where they force fluid through the transmission, are Not Good and usually create more problems than they'll ever solve. It's normal for metal particles (usually casting burrs in the housing) to dislodge and settle in the transmission. Power flushing stirs them up into the fluid, where they lodge in the valves, solenoids, and fluid passages.

A pan drop and filter change is all that's really ever needed. Depending on the service interval, finding some metallic "sludge" in the pan is totally normal; big metal chunks - sans a power flush - are signs of impending transmission doom.

If it was a "power flush", chances are it dislodged some of those particles in the tranny and they lodged in the solenoid valve assembly and in the friction plates. Throwing the codes sets the tranny in Limp Mode (2nd gear). Sometimes shutting the engine off and re-starting it will reset the codes and take it out of Limp Mode if the blockages have cleared. If the code comes back after being cleared, you're going to have to decide what course of action to take: have the transmission serviced to find and repair the faults or weigh replacing the transmission. Read more about the P0731 code here..

The shop is trying to dodge responsibility from the sounds of it. Working fine when it went in, problems after they "serviced" it. Those codes indicate a mechanical, not electrical, problem.