Today I did an oil change on my 2003 Ram 1500 4.7L and afterwards pressure washed the engine compartment with the engine running. Before I had even left the car wash, the check gauges light lit up and the voltage meter wasn't even registering, so I shut off the truck and restarted and it was back to normal.

Then I took it on a 10-15 mile drive. When I got closer to home all of a sudden my engine seemed to rev up quite high so I immediately pulled over and shut it down. Then I started it back up and it was still doing it so I shut it off again. Then I waited a few minutes and tried to start it again and this time it would only crank, but would not start. The error code displaying is P0121. What should I check and fix first in this situation?

Some other engine background that may help:

• installed Fastman TB, new TPS and new IAC about 2 weeks ago, so you know those are clean
• switched to synthetic RP oil and Wix filter earlier today

I would appreciate any help you can throw at me.

 

P0121 is a throttle position sensor code. You got water where it doesnt belong or you knocked something loose or shorted and fried something. But that sensor is your starting point.

 

Thanks, I figured that much already. I just went and unplugged the intake tube from the throttle body and unplugged the TPS/IAC connectors... hoping that drying them out might fix the issue. I'm hoping nothing is fried, but if so I hope it's just a shorted TPS. I will let you know tomorrow.

 

Why i NEVER wash a running engine.

You can buy a batt quick disconnector anywhere. I wash my engines and let them set for quite a while before connecting the batt back up. That engine heat will dry alot out quickly.

I just stay away from the pcm and try not to hit the coil packs directly.

 

Never, ever, ever pressure wash an engine! Technically you should plastic bag ALL intakes and electrical components just to steam clean it (which is the recommended method).

You got something wet, unplug the connector to the component generating the CEL, park in the sun and leave the hood open for a while...

 

Thanks everyone for your input. I did let it dry out overnight but it still would not start. I exchanged the TPS and put in a new one and it fired right up. I also reset the computer when I got home and so far so good.

 

Good deal, it's very possible you may have shorted the other one out...