Digital Dash info needed

[AccordB20A]

There probably wont be ANYONE on the forum that knows this, But does anyone know how the digital dash in the accords figures out how much fuel you have used. Reason is im converting to obd1 and when i was testing my conversion harness today i noted that the liter counter didnt go down even after i went up the road using full throttle. Im slightly worried that there is a wire that goes from the ECU to the digital dash so it can figure oput the injector duty cycle or something?? Anyone know if this is right? If the new obd1 ecus dont have this feature im going to have give up on the obd1 swap cause a fuel milage counter is more important than a tuneable ecu

[frantik]

[2ndGenGuy]

Um, huh?

[A18A]

hahahahahaha

[Civic Accord Honda]

Lol!!!!

[thegreatdane]

there's no wire output from the ecu to the digital dash. There's only the VSS signal FROM the dash TO the ecu.
I dont see any other way except it being calculated from distance travelled divided by fuel used (as measured by the fuel level unit).

[AccordB20A]

okay, well theres a grey wire coming out of the ecu and i believe it goes to that small 3 or 4 pin plug that goes into the digital dash's control box. funny thing is this grey wire isnt on ANY of the pinouts for the PH3 ECU

[AccordB20A]

Found it,


Pin b3, has nothing on the pinouts but it goes to the dash........

[lostforawhile]

are you sure? i know it can use the vss and probably rpms to calculate,but i would think there was something from the ecu telling it throttle position or something. also is there a connection to the map sensor,modern systems use a map sensor in also.

[AccordB20A]

hope i can find a wiring diagram somewhere. it can still figure out fuel usage with the map sensor and tps unplugged lol

[AccordB20A]

hmm i pulled apart a ECU and followed pin B3, it goes to a 10 k resistor and then into the output for injector 2, so i guess thats how it figures it out, gets numbers twos injector times and multiplies by 4 and figures out the fuel usage!!!

[AccordB20A]

Also heres a request for carotman, in the last few days we have been making ob1 adaptor harnesses and we have noticed the following with the pinouts in the error codes/pinouts and obd thread.

the 86-87 JDM B20a pinout needs an oxygen sensor added to C16 as it says there isnt one when there is (my mistake)

and add the b3 being the injector output for digital dash's fuel usage counter on all the B20A pinouts (hell maybe the a20 has it too) The PK2 ECU also supports the digital dash fuel usage thing.

[lostforawhile]

that makes sense, because it knows exactly how much fuel the injector puts out every time it fires, but aren't the b20a injectors that would be the motor it was calibrated on different then the a20?

[AccordB20A]

i guess it will only work for the B20A injectors, But i think most hondas our age have the same injectors. A20 ones will be the same as the B20, That means cheeseburgers one will work accurately on a a series, but if hes swapping in a later b series i dunno how he will get on lol.

So in theori if i got a 10k resistor and heat shrinked the wire in B3 thru it onto injector two my digital dash will work with the OBD1 ecu sicne im using the same B20 Injectors

Ill give it a go some time when my ECU gets chipped

Unless someone here knows if the OBD1 ecu has the same output, Ive pulled the lids off my obd1 ecu but cannot find a 10k resistor that goes to an un named pin and also to an injector

[thegreatdane]

Hmm, I see. That makes sense though, seing how all I have is the KY digital dash wiring diagrams and that the KY model didnt even have fuel calculation.

Where do the other wires go from the small digi dash control box connector?

[AccordB20A]

So far i have found out that the 5 wires that come out of the 5 pin plug on the digital dash control box, they all go into the cars body loom.

theres a yellow, Yellow/Black, Grey, Green/Red and red/black

I only know what the grey wire does, Goies to the ecu so it can work out fuel usage but i have a feeling that the green/red wire is for the fuel light so the digital dash knows when to stat counting down from 10 liters when the fuel reserve light comes on.

I have a hacked up accord loom in the shed, ill trace the other 4 wires and see where they go, So TheGreatDane can get his fuel usage counter to operate

[thegreatdane]

hooray

thx mate!

[AccordB20A]

yeah but heres the bad news, when i remvoed the EFI wires from the accord loom i hacked off the dash plugs too so now i have no idea where anything goes, BOO