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Discussion Starter · #1 ·
Hi piloteers!

I have a 2003 EX-L, and I'm fortunate to be the original owner.
It runs like a dream and I love this car to death.
The only issue I've ever had with it, is about two years ago (!!) my D indicator light started to flash. At first it was intermittent, and then it was all the time. Initially I pulled over and made some phone calls, read a lot about it, and ultimately decided to drive home. At the time I found a lot of mixed info about what this flashing light actually meant, in general just that it was some sort of transmission error code, and it seems like it's a common enough issue that it might warrant a(nother) unique post. It sounds like some people had other symptoms occur that triggered this light flashing, but I had no other symptoms and absolutely no change in drive or shift quality.

I've done a lot more reading about it and fortunately come across some helpful (and very old) threads on this and other forums.

This error code can't be read on a normal OBD-ii sensor, and Honda dealers will charge $135 to attempt to read it for you.
Turns out you can read the code by jamming a paperclip into pin 4 and 9 of the OBD-ii sensor (one is body ground, effectively grounding out the other pin), and turn the key ON to have the dash lights blink out the codes without the fancy reader.
You'll see powertrain, VTM, and A/T codes blinked out by the C/E, VTM, and D5 lights respectively.

I got a code from each, engine code 70 ("problem with the automatic transmission").
I'm assuming that's caused by A/T code 28 "ATF temperature sensor (range/performance, short, or open)".
But I also get VTM code 77, which just says "PCM is defective".

Here's my actual questions for you guys:
Is it possible that simply replacing the atf temp sensor will resolve all of these codes? How possible is it that all of these codes are related? Do those sensors fail in any particular (or repairable) way? Anything else I should try first?
And: anyone know how to reset these codes without the fancy diagnostic thingo? They are stored in memory that can't be reset just by disconnecting the battery.
 

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Nobili spiritus embiggens pequeño sparus tyre.
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Is it possible that simply replacing the atf temp sensor will resolve all of these codes?
Wish I could tell you, but there is one way to find out for sure.

Anything else I should try first?
A standard Pilot transmission troubleshooting protocol around here is:


1. Do a 3x drain & fill (not flush) with Valvoline Maxlife ATF, available at US Walmarts, driving a few miles hitting all gears between each D&F. If that doesn't solve it...
2. Replace the transmission's 3rd and 4th gear pressure switches, another common and relatively inexpensive solution.


anyone know how to reset these codes without the fancy diagnostic thingo?
Some can be reset jumping some pins,



...but the best (an relatively inexpensive) option IMO, short of an HDS machine at the dealership is the Foxwell NT630 Plus scan tool. It'll earn its keep several times over.



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Discussion Starter · #3 ·
I really appreciate the quick and thorough response. I will definitely give the 3x drain and fill a shot.
As for replacing the pressure switches: maybe I wasn't clear enough that I actually get a code 28 indicating a temp sensor problem. There are other error codes that indicate problems with those pressure switches, but those codes aren't thrown. I know that's been the culprit for a lot of people but I don't think I'll replace them preemptively (it seems like most people just guess that's the issue and have mixed results because they aren't able to get a more specific dtc?).

For now I think I'll start with a 3x drain and fill and then grab a "new" temp sensor from a U-pull vehicle and see what happens, and report back.
 

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Nobili spiritus embiggens pequeño sparus tyre.
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For now I think I'll start with a 3x drain and fill and then grab a "new" temp sensor from a U-pull vehicle and see what happens, and report back.
Sounds like a good plan. Keep us posted.
 

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For now I think I'll start with a 3x drain and fill and then grab a "new" temp sensor from a U-pull vehicle and see what happens, and report back.
How long has it been since the transmission fluid was changed (as in drained and refilled even once)?

FWIW, the OEM temp sensor is available for not much more than the cost of the aftermarket parts from RockAuto.
For example: 2002-2007 Honda Sensor Assembly, Temperature (Atf) 28650-RAY-004 | Majestic Honda Automotive Parts
 

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Nobili spiritus embiggens pequeño sparus tyre.
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Unrelated: do you single-handedly account for like 50% of the volume of this entire forum? Pretty rad.
I pale in comparison with some other esteemed colleagues. For example, see directly above. :)

 

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Discussion Starter · #9 ·
@gjexm check out this thread I started a while ago: ATF temp sensor malfunction: code P0713 .

One of the wires leading to the temp sensor frayed and split. I spliced it back together and good to go. Your may be that simple.

--Chris N.
Thanks for the suggestion! It looked okay, but I'll be able to scrutinize it better when it stops raining and I can really get in there. I definitely remember reading this thread and about the thermistor not having polarity, super helpful!

Unfortunately, I don't have a more specific code because there is no obd-ii code being thrown and I won't pay $135 for honda to tell me. (In your case you were able to get 28-4 indicating an open fault, where as I just get code 28 indicating "something's up with the sensor").
 

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Discussion Starter · #10 ·
How long has it been since the transmission fluid was changed (as in drained and refilled even once)?

FWIW, the OEM temp sensor is available for not much more than the cost of the aftermarket parts from RockAuto.
For example: 2002-2007 Honda Sensor Assembly, Temperature (Atf) 28650-RAY-004 | Majestic Honda Automotive Parts
It's been drained and filled (1x) about every 40 or 50k miles. The last one was about 500 miles ago. The flashing D has been ongoing through two fluid changes (though each was just a 1x drain and fill). The light's seriously been on/flashing for ages (about 18 months and at least 60k miles). 🤐
But there have never been any drive or shift quality issues. Never felt it slip or stumble or shift heavy, or anything. No other accompanying dash lights, ever.

And thanks, I guess I could shop around before I go get an ancient part. I'm just a fan of U-pull lots because you can "practice", haha.
 
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