You're welcome and making great progress!

Again, don't replace parts until you find actual problem. Wastes tonne of time and money.

Unless that sub-harness is brand-new OEM unit from authorised Honda dealer, it too is suspect and must be tested before using. Measure each wire end-to-end and confirm it's 0-ohms with no breaks or resistance. When all wires and connector pins are confirmed good, then install it. For that effort, you could've just measured existing sub-harness to confirm it's OK and not causing any issues. Of course, this can also be confirmed by doing test #1. If measuring ref-voltage at source ECM B1 green/orange wire shows same voltage as at MAP-sensor, you would know for sure sub-harness is OK and no need to replace it. Don't waste money on replacing sensors or sub-harnesses when you haven't confirmed they're bad. If anything, you've confirmed MAP-sensor is fine. Why replace it?

Easy to back-probe ECM connector and test for those ref-volt and sensor signals. No need to crawl all over your bike, just measure everything at ECM connector to verify wiring in between as well.

1. First test is measure ECM ref-voltage at source: green/orange wire B1 terminal relative to B12 green ground. If it's NOT 4.7-5.2v, then ECM is bad, replacing all wiring and sensors will do nothing to fix it. This is smoking-gun we're looking for.

It's the ONLY thing you've tested that's out of range and ONLY indicator that something's wrong. Measuring wrong ref-voltage at MAP-sensor is just partial clue, because it could be wiring in between. Go straight to source and see if error is there or not. In which case, that's ONLY part you have to replace.


Just ONE test to solve ALL your problems. No time or money wasted!

 

UPDATE:
Tested the ECT following the maintenance manual and everything is within spec.
Tested the continuity of all 3 cables from the MAP to the ECM and they all show continuity with a total resistance of about 0.4 Ohms each, (did the same on my spare sub-harness as a benchmark and got the same result).
Tested the B1 (Gr/Or) vs B12 (GND) connections on the ECM and did not get any Volts - I have continuity between the two. At first I thought my ECM is dead and I have to spend $400 to get a replacement, but looking at it further I'm not convinced that's correct. At all other points in the circuit the test for the signal wire vs ground shows the same voltage as the signal wire vs Gr/Or - so this means that Gr/Or and GND are at the same Voltage:




Which also got me thinking.... the wire I'm having issue with is the Light Green/Yellow. How can I measure 4.75~5.25V at the MAP end of the cable if the manual says there should only be 2.7~3.1V at the ECM (source of signal)?:



Something doesn't seem to add up to me. Is anyone with a F4i able to do the same test on their MAP and ECM and see if you get the same/similar results as me?

I tried to test the vacuum, but the bike wouldn't start - I think the spark plugs have bitten the dust; there is only so many times that they can be cleaned and put back in, but they came out with fuel on them so at least I know the (serviced) fuel injectors and fuel system are working.

I'm getting very tired of spending my weekends this way.

Thanks again.

 

Hopefully we get your injectors back with before and after flow tests soon.

It's very possible someone previously installed larger than stock injectors in mistaken belief that this would make more power...

 

Sadly I did not get a test report with the returned injectors, but they did come back shiny and new looking, with the old baskets and o-rings included to show that they have been replaced. I know the injectors are the OEM ones as I also have a spare set that I know are genuine and they are identical.
I've been doing some more voltage readings and I'm starting to believe that the MAP is not the problem. I re-measured all of the readings, and this time I took them with both the MAP connected to the harness and disconnected. The results at the ECM end and MAP end of the wiring were the same:


The reading at the ECM matches what the maintenance manual states - its only that 4.2V reading that is low. Did the manual make a mistake; is that reading supposed to be taken with the engine running and some vacuum applied to the MAP? I'm guessing that the voltage output should change with the vacuum pressure and maybe the 4.75~5.25V is the reading at engine idle?
The ECM is not outputting 4.75V on the light green/yellow wire in any arrangement, (the yellow/red wire is measuring at 5.0V at ECM output), so the MAP end of the wiring can never achieve 4.75V - if it did then I have just invented a new form of clean power production.

I would really appreciate if someone with an F4i is able to check their ECM readings and let me know if my ECM is going nuts. Thanks.

 

Urgh... this gets worse.
I swapped the plugs and the bike started like a champ. My new problem is when I tried disconnecting the MAP sensor with the bike running I do not get any FI code flashing. This has to be wrong? Isn't typically a sign that the ECM is no good?
The engine starts to idle faster with the MAP disconnected and settles back down again when I plugged it back in. I'm also getting 2.5V at the ECM on the light green/yellow wire when the bike is running - the manual says 2.7V max, so I'm good there too. What on earth is wrong with this bike?

 

I have another question for the group.
What if i ignore the rich conditions and install a power commander - do you think this would cure the rich running? It would be less expensive than a new ECM.

 

Not having working FI would certainly point to broken ECU. There could be all sorts errors that would normally be registered. Such as MAP sensor out-of-range error when you disconnected it. Might be running out-of-range full time based on those screwy voltages you've been measuring.

Is there someone nearby with known-good ECU you can borrow to test?

F4i ECUs typically go for $325-350 on fleabay. Usually breaker yards give you guarantee it's functional.

 

I have not been able to work on the bike for a couple of weeks, but I finally bought a used ECM that was "guaranteed working" on eBay and installed it over the weekend.
Before doing anything else I re-tested the voltages that I was seeing at the MAP and they are unchanged from what was recorded with the old ECM plugged in.
What did change was that I was suddenly getting FI codes #1, 9, 13 - which is actually a good thing because the MAP and air temp sensor were both unplugged at the time and the old ECM had never given an FI code for these being unplugged when it should have. I also found a lose wire at fuel injector #2 which I fixed and cleared all of the FI codes.
While I had everything apart again I installed a brand new set of Denso iridium spark plugs.
The bad news is that now the bike won't start. It seems that the plugs are not sparking as the engine cranks but makes no sounds like its trying to fire. I haven't had the chance to take it apart again and test for a spark, but I wanted to know if anyone had any issues with Denso plugs before? They get very good reviews online and I doubt that all 4 plugs are bad, so maybe something is unplugged.... I hope.

 

Do you still hear the Fuel Pump priming when you turn the Ignition Key Switch on ?

 

Yes - pump primes, lights turn on, I'm getting battery voltage at the fuel injectors - all the normal things. I have not tested if I'm getting voltage at the spark plug coils yet or if the BAS is doing something crazy. I will probably test for 9V on the pink wire too just in case that has finally died too. I had the bike running just last week and the only thing that changed between then and now is the new ECM and the new spark plugs.

The reason that I question the Denso spark plugs is that they came with a little metal connector on the coil end and I had to take that off to reveal the screw type connection that the NGK plugs have, and I was wondering if maybe I should have left that on?