Lots Of Trouble Usually Serious

[IWILSON]

Hi all, I've got a Lotus Elise (hence the subject ) with a Honda K20A JDM lump in the back of it.

It goes like a cut cat but I have a couple of minor issues still to sort out. I'm not sure what ECU I've got. On the side of the ECU there is a serial number 37820-PRC-013 2070-100532. Does this mean the ECU is a PRC model - if so it's not listed in the ref section. Reason I'm asking is because my O2 sensor isn't working. Whether this is because it's wired incorrectly into the ECU or is just not working I'm not sure. I think it's not a happy puppy because putting a meter across the heater pins (DENSO - so two black wires) gets no reading and I should be seeing around 4 ohms - that's what I see on the old engines O2 sensor. Of course it could have been baked by wrong pin assignment...

Could someone enlighten me as to the correct pin assignment for the O2 sensor. Please specify from which direction you're looking at the plug from (I look at it from the wire side of the plug where you can see the pin number stamped into the plug.)

 

[posol]

Elise's are awesome. =)

PRC... not sure what ecu that is.

USDM K20A3 Civic Si are PNF A01 through PNF A06
USDM K20A2 (RSX Type S) are PRB A01 through PRB A06
USDM K20A3 (RSX Base) are PND A01 through A06
EDM K20A2 (Civic Type R) PRA E02, PRA E03, PRA E11

PRC leads me to believe that it is the JDM K20A ecu (1 up from the rsx S??)

as for the pinout, i don't have that information availble yet.

sorry i can't help more

 

[IWILSON]

I think is must be compatible because it's been remapped by Hondata. In fact I'm sure it's a US ECU becaue we had to make a mod to ECU to get it to work right with the JDM (a resistor needed to be wired in because of a sensor not present on the JDM that the US ECU was looking for - whatever it was it wouldn't allow more than 5k rpm without the resistor in place).

So do the O2 sensor wires go to the same place on the K20A variants?

p.s. It does sub 4 second 0 - 60's. Sub 10 to 100mph with the right tyres and a friend of mine with the same runs a 12.2 quarter mile with road tyres (Engine is untouched internally).

 

[radnulb]

your car: drool

your problem: I thought the K series came with a wideband type sensor from the factory? The wiring might be alittle bit more interesting if that's the case.

again, your car makes me drool.

 

[IWILSON]

Now you're starting to get technical on me

The O2 sensor is a Denso

It's marked as follows:
DU2
DENSO
192400-1090
03D26

Can anyone help...

Pic of serial number

Pic of pins

Pic of Case

Pic of Action

 

[radnulb]

how many wires?

 

[posol]

there are 2 o2's on the k-series... 1 normal before the cat, and a wideband AFTER the cat.

So do the O2 sensor wires go to the same place on the K20A variants?

i see no reason why it would be different.

 

[IWILSON]

It's a four wire O2 sensor. Two black, one white and one green. Black are heater wires, white is signal + and green signal -

Only using one O2 sensor, before the cat.


So where do they go? Answers on a postcard please

 

[posol]

you offically owe me a beer

not the best scans, but these are from an EP3 (2002+ usdm civic si k20) and should be the same for the most part for all k-series ecu's.

 

[posol]

looks like C1 and C16 are the pins for the primary 02, and the other 2 are ground wires.

 

[IWILSON]

I figure I'm getting off lightly with just a beer




Only thing I'm a little confused about is the pin count.

Looking at the photo of my ECU pins.

The left connector has 31 pins next to it 23 pins and the right 31 pins.

I'm presuming that ECM/PCM C is the left hand connector looking at my picture.
If so, I see the Heater output on pin 1 and the PH02S + on pin 16. But no PHO2S -

Making progress I think...

 

[IWILSON]

Which two???

 

[posol]

the ecu is laid out like this...

A1 A3 . . . B1 B3 ... C1 C3... D1 D3
A2 A4 . . . B2 B4 ... C2 C4... D2 D4

 

[IWILSON]

hmmm, just had a mate looking at the pictures of the Manual he reckons there're from a B18 manual not a K20A... You can see the references at the bottom all referring to B18's.

He tells me that PHO2S + goes to A4 and PHO2S - goes to A9

 

[posol]

i see that now too. odd. i got the pic from ephatch.com

i don't know then...

 

[pills_PMD]

update... the prc ECU is from a
Japanese DC5 Integra Type R

found it at this link...
http://www.hondata.com/kprorelease.html
go brian!! you solved another problem without even knowing it

 

[IWILSON]

Thanks Brian, I saw that as well...

The JDM/US ECU unlike the Euro version of the K20A ECU needs to see the heater working presumably for emissions if it doesn't it ignores the O2 sensor. Basically pin A22 needs to see 12+ volts coming from the heater circuit which is switched by pin E8 (heater relay).

This is how I had it wired to start with, before I found the O2 sensor was kaput. Still not sure that there are not other problems since I see 2.1vlts coming out of the ECU sensor + pin A6 - does anyone else see this??? Which just doesn't seem to make sense since it just swamps the output of the O2 sensor. But who knows maybe it's suppose to be this way. An emissions test tomorrow will tell the tale...