SIMJ

Retreived after installing new alternator (it was overcharging the battery), new battery (it leaked because it was overcharged), and ECU (it was fried). Car runs fine. I followed this https://honda-tech.com/forums/honda-civic-del-sol-1992-2000-1/how-pull-cel-d4-srs-abs-codes-code-lists-1901557/ and video is a result of what I got. Can somebody help me read this? What code is it? 10? 20? And is it dangerous to drive with this CEL? Just spent 3 weeks fixing it, and now it throws a CEL at me...

Video: http://www.youtube.com/watch?v=h4nV1gM5wp4

Alexpro

Hi, If i read that right... You got Code 91... 9 long, 1 short...
Here is some info from "http://technet.ff-squad.com/code91.htm"

"This article covers the 'Code 91' (P-code P0453) issue associated with OBD2 civic and integra vehicles.

This problem stems from the type of ecu being used in certain OBD2 civic & integra's. When performing an engine swap on certain 96-00 civic's & 96-01 integra's, depending on what US OBD2 ecu is being used, you may get this pesky code 91 (fuel tank pressure (FTP) sensor) problem. Some 96-98 civics & 96-99 integra's do not have this FTP sensor in the fuel tank which poses as a problem."

SUGGESTED FIXES

1. Change the ecu
The easiest fix, is to use an ECU (keeping within your particular OBD2 version) that doesn't look for FTP sensor. Mainly, a JDM ecu would be of choice, because they are programmed not to look for an FTP sensor.
NOTE: using a JDM OBD2 ecu will not allow you to pass smog, in California at least.

2. Change the gas tank
This is the next best possible solution for alleviation of code 91. Swap out your gas tank for one respective your vehicle type, that has an FTP sensor. Such as running a 99 Si coupe fuel tank on a 97 civic CX or DX. You will more than likley have to wire in the FTP sensor along with adding the FTP equipped gas tank too.

3. Fool the ecu
We fool the ECU by providing a similar voltage that the FTP would normally send -- this happens to be around 2.5v. You need to acquire a 10k linear potentiometer: Radio Shack Part Number 271-1715.
The outter 2 pins are going to be +5v reference and ground (does not matter which), while the center pin will be your output feeding back to the ECU pinout.

SIMJ

Wow this is a massive answer. Tnx man. But is it dangerous to drive. And since it has to do with the gas tank, every time I open the gas tank cap, it sucks in some air, as if there was some vacuum. But it's been doing that forever. I passed inspection pretty recently, so I was wondering if I can drive it for now. Doesn't seem like it affects anything, especially after looking at fix #3

SIMJ

I mean I would love a jdm ECU or SI tank... But expensive

Alexpro

Well that just a troubleshot, you said your old ecu fried... so maybe check if the replacement ecu is exactly same as you had sense there was no problem before it went bad? I would try replace, not upgrade first....

SIMJ

I did replace it with a stock ECU from 97 LX, and I have a 97lx

Alexpro

okay, check if you FTP sensor is still good... sound like you got correct ECU

Vehicles equipped with an FTP sensor:
1996: Civic EX / D16Y8 (All coupes), Integra GSR & possibly LS
1997: Civic HX D16Y5 (All coupes; California sedan: LX)
1997: Civic LX D16Y7 (California coupe; California sedan: LX)
1997: Civic EX D16Y8 (All coupes; California sedan: LX)
1998: All Civic models
1999: All Civic models
(the above list came from a Helms manual)

Vehicles un-equipped with an FTP sensor:
1996: Civic DX/CX hatchbacks, Integra RS
1997: ?
1997: ?
1997: ?
1998: ?
1999: CX/DX hatchbacks

Alexpro

What ECU you got now? Here are the list of civic ecu's:
# P2N : 96+ OBD-2 Civic HX Coupe
# P2P : 96+ OBD-2 Civic EX Coupe
# P2E : 96+ OBD-2 Civic DX Coupe
# P2M : 96+ OBD-2 NZ Civic SOHC VTEC
# P2T : 99+ OBD-? Civic Si Coupe

SIMJ

How do I check it exactly. Also the light is not on and is not blinking while fuel pump primes

SIMJ

A P2E from the same lx

Alexpro

Good Luck testing :D
http://www.youtube.com/watch?v=i0e-Uu4fXTs

SIMJ

opened and closed the tank cap, CEL is gone

Alexpro

Lol

SIMJ

Tnx for help man. Car was parked for 3 weeks, tank was never opened

Kohen

Hahahahaha

SIMJ

Is it a CEL 91? Light came back on today. Car started, ran, than started to dtop RPM's at idle to like 200-300. I always had low idling RPMs, but now it's extremely low. May be since I got a "new" ECU its time to go for a tune up....

SIMJ

ttt

Kohen

Go for it. Try a full tune up. When was the last time it has had one? Maybe run some fuel injector cleaner too. Might wanna clean your IACV.

SIMJ

I got the car about 4 months ago, Idk whn it was done last time... But yeah will deff go and clean IACV and Throttle Body tomorrow... But can it throw a CEL because of clogged IACV and/or Throttle Body???