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ECU version can have BIG impact on MPGs!

76K views 221 replies 37 participants last post by  rschaffrath 
#1 · (Edited)
My 2001 Insight had all of the recalls done in ~2008 and had the 070MCM/A01BCM, as well as the 37820-PHM-506 version of the ECU/ECM when I got it last August. I have slowly replaced the BCM/MCM to revert to the original versions as I documented in this thread in an effort to maximize MPGs without using the MIMA system. I have peacked in the high 80's to low 90's MPGs while driving on flat open highways at ~45 MPH and that, I thought, was the best I was going to get . . .

The 2000 Insight that I recently bought from Oregon and am fixing up to sell to a relative had no recalls done, and had the original 030MCM/010BCM (which Eli now has ;)). Interestingly, it also had the 37820-PHM-505 version of the ECU/ECM.

Since I am in good with my Honda parts guys and they will chip keys for me free, I figured what the heck and tossed the 505 ECU into my 2001.

I was, and still am, shocked at the result. I got an immediate 8-12 MPG improvement at all speeds! I am now able to drive 55MPH and get mid 90's MPG on my 'flat' commute. Before I had to run a 45MPH target speed (and less on hills) in order to break into the 90+ MPG range. I have never been able to run low 90's MPGs during my normal commute without going VERY slow, and mid/high 90's required the full tank "bump" to achieve.

This was driving home on the 'flat' route at a 55MPH average. This is easily my best MPG ever on this late night run, AND I was going approx 10 MPH faster than normal:



I haven't been able to do a normal 'hilly' route test run (at ~45MPH) where I get my best MPGs, but was able to slow to ~45MPG for a few miles on the 'flat route' during my drive in to work a couple days ago and got this:



I have *never* been over 100 MPG for this type of distance, let alone close to 110!

I've been driving on this ECU for three days now and am still amazed at the increase in #s I am getting. I am seeing this significant improvement at all times and all speeds, regardless of terrain or gear. I am not sure exactly why this jump has occured, but I have noticed that the car will go into lean burn faster/easier, auto stop happens sooner and more often, and purge cycles are much less frequent, but those don't add up to this increase by themselves. There is no difference in power or acceleration, and nothing else on the car has changed. I have intentionally been driving on less then 1/2 tank to ensure the "fill up bump" is not skewing my numbers.

I should be able to get three full test runs next week and will be sure to post those results, but this was too shocking for me to wait anymore.

Needless to say, my relative is not getting this ECU back :p
 

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#2 ·
Crap.. Now I'm going to have to start collecting ECMs.

:D

So you have to re-program your keys when you swap ECMs? I didn't realize that.
 
#4 · (Edited)
Correct. That was the only change that I made relative to my prior MPG #s I mentioned. Each ECU has an unique immobilizer chip in it that they keys must match in order for the car to start, so if you buy one online (eBay) make sure you can get a key from the donor car with it. With the key the parts department can copy the "chip" from the donor key to one that has been cut for your car. Without the key it takes the service department to plug into the car with the new ECU in and make a new set of keys (much more $$$).

I also wonder how the 37820-PHM-355 ECU would compare to the *505 revision. Anyone have a *355 laying around (with a donor key) that want me to test? :D
 
#16 ·
I saw several on eBay. Strangely I saw many *345 (the one with the o2 sensor bug) and many *506, but no *355 or *505. I think with patience one could be had for cheap . . .
 
#9 · (Edited)
Hmmmm, now I need to go pull back the passenger foot well cover and get the numbers off of my ECU. I'm curious to see if it has been upgraded since I'm the fourth owner and don't know the complete past history on this vehicle.

EDIT:
So to clarify is the version the number on the sticker like on the BCM/MCM?

I looked at mine and it has this number on it: 39980-S3Y-0032 (Never mind, I got the numbers off of my EPS module)
Does someone have a list of what the different EMC versions are?

Will have to take a better look for the ECU tomorrow when light and access is better.
 
#11 ·
#12 ·
I saw the BCM/MCM spreadsheet (first tab)and saw the ECM's on that list, I didn't see that the ECM has its own tab on the spread sheet also. So is it possible that if I do go through the trouble to dig down to the ECM and get the PN off of it that it could still have a newer version of software loaded onto it that I would be unaware of?

I saw the note on the first tab of the spreadsheet that you need a reader to actually see what version of software you have loaded. Just don't want to tear the car apart to get a PN off the ECM if the version on it is completely different.
 
#13 ·
We don't technically really know what the hex code displayed means. We'll have to get more data to see if different ECM revisions have different codes. Only 2002+ ECMs are flashable, so 00 and 01's should be pretty consistent at least.
 
#91 ·
From the spreadsheet I count at least 3 "early" versions, all beginning with the number 3, and the 505 and 506 which Honda apparently started putting in at some point.

I think this is going to be very tough to sort out in terms of the "best" from an MPG viewpoint. FWIW, I can top the mileage that Jeff is talking about with my 2006 MT. On my calibration "track" of 54 miles, target speed 50 mph, I can achieve 100mpg or better, spring through fall - no MIMA, no FAS. So I don't see that we are really proving anything yet. Maybe there will be some ground truth, but I don't think we have found it yet.

I certainly respect Jeff's work and appreciate all that he does. Perhaps he is dealing with worse traffic than I on my calibration "track" which is all Interstate limited access, but that is kinda the point. Diamond Larry is out in mostly flat Wakarusa - I've seen it personally. So conditions of terrain and weather vary all over the place and the car is super sensitive to both, as well as driving skill. I don't want to say that finding the right "box" is impossible but it isn't going to be easy:D JMHO
 
#18 ·
These are the ECM revisions that I found on eBay a couple of weeks ago with a quick look.

Code:
[b]ECM	        Year QTY seen	Notes[/b]
37820-PHM-A53	2001	1	
37820-PHM-505	2000	4	
37820-PHM-316	2001	3	
37820-PHM-345	2001	8	
37820-PHM-A02	2001	4	
37820-PHM-A13 	2002	2	
37820-PHM-A63	2006	1	
37820-PHM-A52	2001	1	Typo?
 
#19 ·
Nice. All I've been able to gather/confirm so far is that the *345 was the original on the 2000, and had the o2 bug - and was superceeded by the *355, and the *505 was original on the 2001 and was superceeded by the *506. I am not 100% sure on this, so feel free to confirm/deny. I think the Axx versions are 2002 and later . . .
 
#20 · (Edited)
Well chuck what I just said out the window. Per HPN (HondaPartsNow.com) part database:

MY 2000: 37820-PHM-A01, Replaced by: 37820-PHM-355

MY 2001: 37820-PHM-326

MY 2002: 37820-PHM-A14, Replaced by: 37820-PHM-405

MY 2003: 37820-PHM-A14, Replaced by: 37820-PHM-405

MY 2004: 37820-PHM-A16, Replaced by: 37820-PHM-406

MY 2005: 37820-PHM-A21, Replaced by: 37820-PHM-407

MY 2006: 37820-PHM-A25, Replaced by: 37820-PHM-408

I highly doubt this includes all recall/in between versions, but at least it gives us something to work with.
 
#49 ·
Well chuck what I just said out the window. Per HPN part database:

MY2000: 37820-PHM-A01, Replaced by: 37820-PHM-355

MY 2001: 37820-PHM-326

MY 2002: 37820-PHM-A14, Replaced by: 37820-PHM-405

MY 2003: 37820-PHM-A14, Replaced by: 37820-PHM-405

MY 2004: 37820-PHM-A16, Replaced by: 37820-PHM-406

MY 2005: 37820-PHM-A21, Replaced by: 37820-PHM-407

MY 2006: 37820-PHM-A25, Replaced by: 37820-PHM-408

I highly doubt this includes all recall/in between versions, but at least it gives us something to work with.
Now you really got me confused Jeff:?

You own one each of every year? And the current ECM #'s installed are as per this post? And the original post was in error?

Just trying to understand the logic:)
 
#21 ·
I found a 505 and a 345 on Ebay. The 345 is brand new and in the box and is a bit pricey at $253.50. The 505 was only $99.;)
 
#22 ·
I really need to find out what my cars have.

Maybe one of the other cars has a 505 I could swap in. Then I would just have to swap keys eh? :D
 
#26 ·
The cheapest way to do back to back testing is to get a $0.99 key cut at the auto parts store (a 90's civic blank will work) then tape the ECU matching chipped key to the non-chip key to please the immobilizer. It will NOT work if both keys have a chip. The immobilizer must only see the matching key and nothing else. I've tried this a lot in the last few days and had a 0% success rate when using two chipped keys (one matched and one not) at the same time.
 
#27 ·
Hmm....

I have all of my Insight keys on one keyring and I've never had a problem. Or maybe I didn't understand what you just said. lol
 
#28 · (Edited)
Fair point. I think proximity matters. I've been trying to hold the keys back to back/side by side as the diagram in the FSM (Factory Service Manual) shows. Of course I have only tried this with the non-matched key being the one inserted in the ignition. I think the sensor field is so small that the ones on the key ring are not 'activated'.

I will try it the other way in the morning - with the matched chip key in the ignition and a non matched key held in close at it's side and report back
 
#29 ·
Time for some data gathering on the imobilzier data lines i think ;)

If we record the data it transmits back and forth to the ecm with a good key and a bad key we may be able to decode it and then have a gizmo just send valid codes whatever key is inserted into the ign. Obviosusly it makes your car less secure. Further study of the wiring diagram at this point would also be useful.
 
#30 ·
Seems like the key is going to be the problem. I truely dont think that getting a 505 off Ebay is going to come with a key. Ill spend the money for an ECU in a heartbeat but I will bet that getting the matching key will be tough...or VERY expensive. And Honda isnt going to help ME..we arent on speaking terms after them refusing to warranty a 3 month old 12v battery.
We need a way to at least temporarily get past the immobilizer, get to a (gulp) dealer who can read the ecu and program a key.
 
#31 ·
Worst case scenario, mail them to me, my dealer will do it for me for probably the best price out there. But first let's look into retepsnikrep's possible code workaround or Katman's replacement IMM chip . . .
 
#35 ·
Before people go out buying 505 ECMs, and trying to get keys, I think we need some more information. The only thing that's established here is that the 505 is likely better than the 506, in terms of fuel economy. But that doesn't mean the 505 is better than all the other numbers. Perhaps it just means the 506 is weak along these lines...
 
#38 ·
Before people go out buying 505 ECMs, and trying to get keys, I think we need some more information.
And my question is what is the tradeoff. So the 505 perhaps gives you better fuel economy. Is there something that we lose with it? Or perhaps does it increase the risk of presenting another problem? Honda made changes for a reason or reasons. We may not like all of the reasons, but regardless, do we know all of them?

-Bryan
 
#36 ·
Too bad it wouldn't be as simple as plugging directly into the "new" ECU...kind of like Peter's disembodied "car" on the test bench for the dealer to reprogram the key?:)
 
#39 ·
Not all changes are good for consumers as was the case of what Honda did with reprogramming updates that destroyed the FE of their vehicles and made it virtually impossible to achieve the original EPA ratings.

Jeff, part of the reason I'm so interested in this swap is that I'm going on a 225 mile road trip to see my daughter in Columbus, OH on Easter weekend and that seems like a perfect test. Paying expedited shipping charges would even be an option.;)
 
#44 · (Edited)
Not all changes are good for consumers as was the case of what Honda did with reprogramming updates that destroyed the FE of their vehicles and made it virtually impossible to achieve the original EPA ratings.
I agree 100%. Likewise, not all changes are necessarily bad for the consumer, either. I still wonder if we know everything that is different between the versions. Didn't some the more recent ECM upgrades prevent false alarms about CAT problems?

-Bryan
 
#41 · (Edited)
It appears some of the earlier ECM's had a way around the programmed immobilizer key. Not certain this applies to Insight but ...

"Replacement ECMs/PCMs
May Give Free Engine Starts
Some replacement ECM/PCMs are programmed to
give 10 free engine starts before you need to use a
programmed ignition key. These free-start ECM/
PCMs are intended for the production line, but
occasionally, they may get put into parts stock by
accident. .. ..[snip]".
Unlikely running into one of those, but the potential was there obviously for a defeat of the code.

from a021100 Honda ServiceNews oct'01 in repair manual appd.

_________________
And it is written about an immobilizer code replacement procedure below:

Saw this for Honda's HDS: after noting year changes year in later models vin entry, latter part aludes to a rewrite procedure :
ECM replacement procedure
[excerpt:]
NOTE: For 2005-2006 models: DTC P0630 "VIN Not Programmed or Mismatch" may be stored because VIN has not been programmed into the ECM; ignore it, and continue this procedure.
14. Rewrite the immobilizer code with the ECM replacement procedure in the HDS; it allows you to start the engine.
*********

And wondering about KManager if it would allow to reprogram insight ecu immobilizer and possibly more from a laptop? [appears it doesn't have application but perhaps some may be similar]
_______

My 2000 Cdn car had a 37820 PHM 506
in 2008 swapped in per K66 recall, replaced on warranty with
Bulletin: LOP121100....DC 5PW CC K66
[obdiic&c ECM # 6C 01 11 00 00]

Any indications what each changeup accomplished would be interesting. I'd be anxious to retain any cold weather charging alterations, or have the option of changing out the unit seasonally with no immobilizer hassles, but then Lmpg and all would change too?
 
#43 ·
Interesting. This brings up something I was wondering about earlier: Wouldn't it be the imobilizer unit that actually tells the ECU whether or not to allow an engine start?
 
#57 ·
I have both the 505 and 506 ECUs and they both operate identical in my 2000 Insight.

There is no mileage difference between the two. I have tested both in winter and summer, without observing any difference in performance or mileage.

I bought the 506 from Brent about a year and a half ago for $40.
 
#58 ·
:D

Yea, I'm not surprised, and thanks BTW for the data. I think that these little gems are damnably hard to get a handle on FE(fuel economy) wise. Between the fact that different folks drive differently, and the fact that there are a whole host of folks with different techniques, equipment(i.e. MIMA, grill blocks, etc.), and driving conditions, the FE is nowhere near a stable number. The government reduces it to a fixed number, under some ideal conditions, but in the real world the FE varies wildly. I've seen folks who seem pleased with 65-70 MPG while others see 150 MPG as the goal - count me there;)

Some have no understanding of what makes FE, some have a course understanding of what makes FE, and some have an excellent, though not complete, understanding. Perhaps it is like life and the real kicks are in the search:D
 
#59 ·
Brake plus gas = fast chance... NOT.

Forgive me for I am a newbie and know not what I do.
BUT...
In heavy stop and go traffic. I must drive very carefully (weirdly) to prevent
144v battery from becoming discharged on my 2000 MT, unmodified.

Seems to me that if I hit the gas and lightly ride the brake, it should give a rapid recharge.
But it doesn't. And that is a Honda engineered failing.
Any easy-cheap-quick fix?
 
#64 ·
Forgive me for I am a newbie and know not what I do.
BUT...
In heavy stop and go traffic. I must drive very carefully (weirdly) to prevent
144v battery from becoming discharged on my 2000 MT, unmodified.

Seems to me that if I hit the gas and lightly ride the brake, it should give a rapid recharge.
But it doesn't. And that is a Honda engineered failing.
Any easy-cheap-quick fix?
Yes, MIMA. Stock, the systems will not allow regen if you're hitting the gas.
 
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