AnthonyMtz

Ok so as I recently posted about my transmission issue's, I now have just witnessed my rpm gauge literally drop to 0 when I was driving and then randomly jumping up and down, never had this issue before..could this possibly be a sensor or short? I tried doing some research and unfortunately I didn't find anything about the rx's

kalali

Unfortunately (or fortunately) you won't find this being a common issue. The tach quit all of a sudden on our RX (now with the mother in law) a few months ago and I couldn't find anything out there to help except the suggestion to disconnect the battery for a few minutes - from our friend Salim here. It worked. Give that a try. Someone also posted a diagram showing a sensor somewhere near the end of the transmission but no matter how much I looked I couldn't physically locate it. Do a search and you'll find my original post.

AnthonyMtz

Thanks so much, I will try disconnecting my battery for a little bit, perhaps it's a ecu issue..., did you're tach start working again? Again I appreciate the help.

kalali

I think it did. The only reason I'm not 100% sure is because I disconnected the battery when she stopped by for a visit and the tach was working right after I checked. I can't be sure if it had started working when she arrived. Of course when I asked her the question, she said she never looks at that gauge. Interestingly enough, I was the one who discovered the tach not working in the first place. She had no clue how long it had been broke. Easy enough to check.

AnthonyMtz

Thank you!! It's now working after the disconnected battery

salimshah

Little bit of insight here:

The rpm display is electromechanical. ECU gets the rotation info from the crank. ECU internal clock then calculates rpm and sends the info the meter. Crank information along with cam information is used to produce the spark at the right time.

Net is if the engine is running fine the problem most likely is in the ECU calculation of rpm. There can be a hardware problem, but it can be a software issue due to some gremlin. A simple reboot (term for AIX) or restart is needed for the ECU.

RX does have some portion of restart of software loops when you turn the ignition off and on next ignition on but not all.

Salim