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Q: Can a high pressure pressure wash of an engine cause multiple electrical problems? on 1995 Toyota T100

About 2 weeks ago I took my 95 Toyota T-100 into a local Toyota dealer for an oil leak in the valve cover gaskets. They cleaned the whole top end of the engine (intake manifold removed and cleaned in ultrasonic cleaner, and used some kind of degreaser and high pressure pressure washer to clean all other top end components, front, sides, back, and bottom of engine) and had both valve cover gaskets replaced. In the process they blew off my cruise control retaining ring (my first clue, but an easy fix). After cleaning, they discovered I also had a rear main seal leak. Both leaks were very minor, but as I fastidiously keep my truck maintained I wanted them both repaired.
$1550 later, and immediately after getting the truck back I discovered a "check engine" light which I checked with my Acctron OBDII computer and it gave me a P0170 code. I had never gotten this indicator before I had any service work done.
It is now two weeks later, and last Friday my transmission would not move in 1st gear. I had to manually put it in L (low) to get it moving, and then shift up manually. Then the O/D light indicator started flashing. I immediately stopped and checked the transmission oil level, and it was dry. It took over a quart to fill it. (and I use Mobil 1 synthetic ATF, so it's not cheap). The O/D light stopped flashing, but the shifting problem remained. I decided to check the OBDII status again, and now I am getting a P0170, P0753, P0758, and a P0773 code. I have tried to look up these codes thoroughly, and they all seem to be electrical in nature... (MAF sensor. and Shift solenoids)

So, my main question is this: Do you believe (as I do) that the High Pressure pressure washing (which they did TWICE by the way) caused these electrical problems to start all showing up at the same time.. just after they did their work. I have used "Engine Brite" degreaser for many years on this engine (the truck is 16 years old with 233,000 miles) and I know better than to use a pressure washer on it. I only use a regular garden hose and my thumb, and I have NEVER had a problem or a check engine light after this maintenance. I would like a professional opinion to take back to the dealer. Thank you.
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You are absolutely right, high pressure washer could cause electrical problems since water could enter into connectors and components.
There are a bunch of transmission related codes, and since they had to remove it to get access to the rear main seal they could left a a connection loose - or perhaps water entered into the connection.
To disconnect he electrical connectors on older Asian vehicles could be a pain sometimes and I have seen bent pins due to jerking and bending.
I'd definitely take it back to the dealer and ask them to check everything they have done.

Not an answer but what ended up happening with your truck. I have 200,000 miles and I just washed my engine and all of a sudden it will not shift except at redline. I really hope this just "went away" but please let me know.

Thanks much,
There is no absolute answer but is very suspect. By immediate do you mean as soon as you started and left the lot or hours/days after? If was very quick or within the two weeks you should have let the dealer know your suspicions asap. If you have a good rapport with the dealer and keep your calm and appeal to their fairness then will go a long way. Keep a cool head and let them know of your maintenance/cleaning procedures and see what they say. If they care maybe they can meet you half way. Good luck.
If you had the work done at the Toyota Dealership, I'd take it back and let them check it out. Using a pressure washer can cause electrical problems, but I've cleaned my engines that way in all my vehicles included my 95 T100. If electrical connecters are old they can stop working at any time. The pressure cleaning that the techs done probably just made the connecter, sensor, or other electrical part just show up sooner ( meaning it was already going out). Just don't try pressure washing the electrical parts themself and you shouldn't see any problems from cleaning your engine this way. The only way I can see the pressure cleaning really hurting your vehicle is if your trying to use a high industrial pressure cleaner. If you need anything else you can reach me on the site
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