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So recently the Service Engine Soon light has come on in my truck. I brought it to the shop and had them check what code the truck was reading. It said P1774. P1774 stands for: Possible causes Faulty Low Coast Brake Solenoid Valve Low Coast Brake Solenoid Valve harness is open or shorted Low Coast Brake Solenoid Valve circuit poor electrical connection. Now this code is not very clear as to what I need to focus on fixing since there are several things that could need fixing. Does anyone on here know enough to be able to help me find the specific problem? I can provide additional information as needed. I am triying to fix this truck without breaking the bank. Anything will help!
 

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Most of those I've heard of ended up replacing the transmission TCM/control valve assembly. Unfortunately, it's not a cheap repair. The labor isn't so bad, but the price of the parts are. And if I'm not mistaken, a new TCM/valve body has to be initialized to the vehicle once installed using a CONSULT III or similarly capable scan tool. Nissan doesn't sell the transmission solenoids separately, but, I have run across individual shift solenoids for this trans in the aftermarket, online, with a little searching. Perhaps a transmission shop may be able get one?
 

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I've done a little bit of research and I've come across a couple of online vendors who sell individual solenoids that SEEM like they're easily swapped out.

Putting the valve assembly itself aside for now, the code (P1774 - low coast brake solenoid valve function) indicates that the probable cause is either "Open or short circuit condition" or "poor electrical connection".

The way I'm interpreting that is the connections to the low coast solenoid valve might just need to be replaced. Does that seem like a plausible solution to this? And is it a less expensive fix as a result?

I need this vehicle up and running as soon as possible and given my busy and inconvenient work schedule, the sooner the better. Any input/links to possible parts I may need would be hugely appreciated.
 

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You have to remember that the solenoid's internals are part of the circuit, so, if there is an internal short or open inside the solenoid, it will trigger the same code as a bad connection. You need to follow the TSB linked to above along with the factory service manual to perform the diagnostic procedure and circuit checks for the given code to isolate the exact cause. This, keeping in mind that the factory service manual may recognize the fact that that Nissan does not offer the solenoid(s) other than as a valve body assembly. Usually there is a way to disconnect one of the harness connectors and perform a resistance check of the solenoid; the service manual would have this procedure in the diagnostics for DTC P1774. I do recall some issues caused by water getting into a harness connector above the transmission, as well, which might be something worth looking into. Also, most harness or circuit issues do not usually require replacement of the harness connector; it is usually a broken wire, corrosion or bent pin issue that needs to be repaired. The only time a harness connector usually needs to be replaced is if it gets hot and melts or if it breaks apart.
 
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