accordianex

I was throwing an o2 code.
so i changed the o2 sensor
reset the ECU by pullling the ECU fuse in the engine bay
strated up the engine, the CEL came right on. let it run for 15 mins so ECU can do its thing.

shut if off, still get o2 code.

reset ECU again, this time i pull code before turning back on.

o2 code still there, its still throwing a CEL even though i reset the ECU.

whats wrong with my ECU???

EE_Chris

You need to give more info....like the car/engine/mods.

Which code: 1 or 41?

Relic1

"reset the ECU by pullling the ECU fuse in the engine bay"
there's a problem. you pull the backup fuse not the ECU fuse.
The ECU fuse powers the ECU when the ignition is on, the backup fuse powers it when the ignition is off.

DannyDeuce

Unhook the battery......that will reset it.

DAN

accordianex

ok, ill try un hooking the batt

and its a
93 SI hatch back
D15B Vtec
P08 ECU
One Wire O2 sensor, and yes the wire is going to pin D14 on the ecu.


what is the right fuse i shoule be pulling instead of the ECU one in the engine bay?

accordianex

CEL still on

pulled neg batt terminal the second i started the car after, the CEL was on.

Relic1

the right fuse is the "backup" fuse that sits right next to the ECU fuse.
It's a 7.5 amp fuse.

Has the car ever ran with the P08 and one wire O2 without a CEL?
(to know if it could be a wiring issue or if it's something that has gone bad over time)
Are you getting code 1 or 61? (or even 41?)

once again EE_Chris seems to be two steps ahead of the rest of us...

accordianex

no it has not ever run with out a CEL

its a code 1

and i check the wire, i ohmed out from the o2 sensor to the d14 pin on the ecu and its a straight path like only 20 mili ohms of resistance there, so its a good conection.

ill check again once the weather gets above 20 degrees lol.

Relic1

is there voltage on the wire when the car is running?
there should be ~.5V. it will move around of course... depending on the A/F in the exhaust, but it should be between .15V-1.05V
You could have shorted the wire to the sheild some how which would cause ground to be to the pin, which would cause the CEL.

accordianex

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Relic1 &raquo;</TD></TR><TR><TD CLASS="quote">is there voltage on the wire when the car is running?
there should be ~.5V. it will move around of course... depending on the A/F in the exhaust, but it should be between .15V-1.05V
You could have shorted the wire to the sheild some how which would cause ground to be to the pin, which would cause the CEL.</TD></TR></TABLE>
ill check that out, thanks

schardbody

man, still having problems with that o2 connection. hope you figure it out. you have verified that its a p08 and not a p28 right.

accordianex

ya its a P08

schardbody

hmm, that sucks. might have a dead one... i dont know.

Syndacate

ya....pull the battery + terminal and wait 10 min to reset the ECU, don't pull the fuse..

it's like using a cutting torch to take apart your stereo..

Certain ways of doing things..

Reset it the normal way (make sure the fuse is in when u unplug the battery), then unplug the + term, wait 20 min, put it back on, the CEL will probably stay on because u have an O2 problem or whatever, but reset the damn thing normally first..

then jump the switch and check ur codes..

accordianex

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Syndacate &raquo;</TD></TR><TR><TD CLASS="quote">ya....pull the battery + terminal and wait 10 min to reset the ECU, don't pull the fuse..

it's like using a cutting torch to take apart your stereo..

Certain ways of doing things..

Reset it the normal way (make sure the fuse is in when u unplug the battery), then unplug the + term, wait 20 min, put it back on, the CEL will probably stay on because u have an O2 problem or whatever, but reset the damn thing normally first..

then jump the switch and check ur codes..</TD></TR></TABLE>
hmm, i keep pulling the neg terminal maybe ill try the pos one.

Sliced Beard

never unhook the positive terminal first......great way to blow fuses and short out wires. It induces a high ampreage jolt throug out the electrical system which can destroy many things including your ECU.

I suggest looking to see if you have a broken wire at the connector. If you have a good connection you should be fine. Your car runs in Closed loop until it reaches a specified temperature then it runs in open loop. Your car should not set off a CEL until after the car is warmed and in open loop. So there is something wrong elsewhere.

accordianex

ok first i checked to see if the o2 was shorted to ground, it is not

then i pulled the pos terminal of the batt for like 10 mins

started her up, the CEL came right on

checked the voltage of the o2:
at running tempurature the o2 is sending a signal of .08V to .10V

which i think is low.

i unpluged the harness for the o2 to see if something was loading it down, and nothing is.

this is a new o2, wtf.

any ideas guys?

EDIT: too late on the pos terminal thing.

so if im throwing a o2 code, what could be the problem if its throwing the code before it reaches open loop?


Modified by accordianex at 1:24 PM 3/4/2006

Sliced Beard

sounds to me that there may be an internal glitch within the ECU. I think the P08 looks for a 4 wire o2 also. You may be getting a code because of the o2 heater circut not working. A four wire o2 has two grounds one for the heater circut and one for the sensor ground, heater power and referance wire to the ECU. Your CEL is likely coming on due to the fact that the heater ground (the ground is turned on and off by the ECU internally) is not getting a voltage reading immediately setting a code.

accordianex

i have a four wire o2 as well, and it was hooked up, but it was throwing a code as well

do you know what pins does each of the wires from the o2 goto on the ecu??? (FOR THE FOUR WIRE)

Sliced Beard

I don't remember which pin goes where but I am sure it is not too hard to find. I forgot the guys screen name but he has a web page with a TON of pinout diagrams and whatnot.

schardbody

p08 looks for a 1wire, the p28 is basically the same but looks for the 4wire o2. only thing i can come up with is a bad ecu. thats considering the o2 is hooked to the correct pin on the ecu. the only thing it really can be if the o2 is new is the wiring or the ecu. the ecu looks for voltage before open loop at the o2, so if you have voltage out the 02 plug check it at the ecu, could be a broken wire. possibly run the o2 directly to the ecu pin.

accordianex

like i said before, once its warm enough to do that, im going to run a wire right from the o2 to the ECU.

2lua

did you tried to jump the service connector? if you are remove if and see if it still have cel on. if you did then try a known good ecu.

accordianex

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2lua &raquo;</TD></TR><TR><TD CLASS="quote">did you tried to jump the service connector? if you are remove if and see if it still have cel on. if you did then try a known good ecu.</TD></TR></TABLE>
what?
that didnt make sense, sorry

if you mean did I jump the two pin connector on the passenger side to get the code, then yes.

it just blinks, over and over, a long beep no short ones, never stops beeping so i assume its a code one.

Relic1

"at running tempurature the o2 is sending a signal of .08V to .10V"

that is a problem. .1V from a standard O2 sensor is in the 17:1 - 16:1 range. lean even for idle. It should typically be between .3V(15.4:1) and .6V(14.4:1) at idle.

This indicates a bad O2...
Unless (to throw another thought out there) your engine's grounding isn't perfect.
A one wire O2 relies on the header--&gt;engine--&gt;engine_ground for the negative side of the O2 sensor path. If it's flakey or not a good connection it will show lower voltage than it should and do what you're seeing.