BayLude

So my 1998 Prelude's Check Engine Light (CEL) light came on. I didn't have a scan tool and in the state of California it's illegal (for whatever genius reason) for shops to give us "free scans" now, since a couple-few years ago actually... so I just bought my own scan tool online after finding one for pretty cheap (Autel MaxiScan MS310 - for those interested). I just plugged it in tonight and received the following codes:
P0700 , P1791 , P0740 , P0730

The description by the scan tool for each says:
P0700 = "Transmission Control System (MIL Request)" -- this one, from what I've been reading, just sounds to be some generic code (to basically turn the light on)
P1791 = "Vehicle Speed Sensor (VSS) Range / Performance Problem"
P0740 = "Torque Converter Clutch Circuit / Open"
P0370 = "Incorrect Gear Ratio"

Looking these codes up online.. I've only found people who seem to have been presented with symptoms much worse than mine - I guess this is good news?

The Check Engine Light came on when I was driving down a side-street and about to make a turn (I only mention this because from what I've read, this seems to be relevant.. what I was doing when it turned on). I couldn't have been going more than 40-45 MPH. I have the base model, with the Sport Shifter.

NOTE: When my Check Engine Light came on, my D4 Light started blinking at the same time.
I subsequently calmly pulled over, kept it on for about a minute or so, slowly ran through all the gears (to see if anything else triggered by chance), then turned it off. None of my electronics or anything seemed to be dead (ex: my clock was still on), and my windows didn't randomly roll down or anything (reading online, some people mentioned that for some reason their windows rolled down when this - the D4 Light blinking - happened, upon turning off their car).

I turned my car back on, and my D4 Light was no longer blinking, though the Check Engine Light was still on. I had the thought of taking it up to 4th Gear back on the main road to see if anything noticeable would happen (figuring that, by 4th gear, I would've run up to and through the point that the blinking light seemed to indicate experienced an error). Now this was the weird part. NOTHING out of the ordinary was happening. Nothing. No shift shock, no high RPM's, no lagging downshift, nothing. Neither at that point or at ANY other point on the drive home did anything noticeable happen. My Tachometer and Speedometer, Fuel Gauge, etc. are all still functional (i.e. they're not dead, as I've read a few times online people with a D4 Light blinking reporting that their Speedometer doesn't go above 0 mph, or similar). I've since driven it a couple-few times short distances (while I waited for my code scanner to arrive) to see how it feels, since I was wanting to see if any symptom would present itself ("why did the Check Engine Light come on?"). NOTHING has been different whatsoever.

I've since described it to people as this: "If you were to take away my dashboard and I couldn't see the Check Engine Light, I seriously wouldn't even know or even guess anything to be wrong. It's completely normal. NOTHING feels different when driving my car, and I'm very attuned to my car when I'm driving it."

The last time my Check Engine Light came on (about a year ago), I just checked and added new Transmission Fluid and the Check Engine Light eventually just turned itself off. Reading around, I'm wondering if low or dirty transmission fluid could be the cause of this again? I had my transmission completely rebuilt a few years ago (~3-4 years ago) and I haven't had any issues with it other than these occasional random Check Engine Lights coming on.. but they never seem to actually be anything. I'm coming to you guys for your expertise, and opinions on the matter as I respect your guys' opinions here on this forum.

So, what do you guys think? Do you think, after reading the above, that I should just clear the codes and see if they pop back up again? Is it normal for these codes to appear and literally have ZERO symptoms present themselves? Could it have just been a 1-time fluke or instance that triggered the Check Engine Light to come on? Because again, it baffles me how I seriously feel nothing different driving the car, and I'm always very aware and attuned to my car.


Thanks guys! I look forward to your assistance!

nemesis25

Sounds like your speed sensor is gone. I have one for sale on Ebay.

BayLude

Why/How would this cause "Torque Converter Clutch Circuit / Open" and "Incorrect Gear Ratio" codes to be thrown?

Anybody else with any further opinions? They're ALL appreciated! Thanks guys for any help!