General 99 gsx ecu in a 97 gst

[fantom73088]

I have recently purchased a 99 gsx ecu to put into my 97 gst. The car runs great but throws an evap code is this becaue from 97-98 they changed the evap system and how can I fix this? I also have a 98 gst this is how i know the evap systems are different. Is it possible to put a 99 evap purge syloniond on a 97? Any input would be great.

Thanks, Adam

 

[nek]

2 things come to mind. neither might work for you.
1) dsmlink can clear codes but Im sure you dont wanna spend that much just to fix codes.
2) If its for inspection. reseting your ecu by pulling your battery clears codes for a certain amount of time. My fuse that controlled my interior lights and my radio was lose caused my ecu to reset everytime I turned ignition off.
But if its for piece of mind, not sure how you would fix it.

 

[the_mork]

It shouldn't throw a code unless there is something wrong with the evap system. Any perceived differences are irrelevant to your ecu.

If it bothers you then consider how to fix your evap system or go out and buy an openport 2.0 cable so that you can flash the ecu, assuming your 98 still has its original ecu you can use the cable to flash both cars although you'll need to find a flash port at a junkyard to install on your 97.

 

[luv2rallye]

Is it possible to put a 99 evap purge syloniond on a 97?

They both have an evap purge solenoid but the 97 does not have a evap emission vent solenoid where the 98 & 99 (and all NT) do. Not sure how this would effect the ECU choice. PM Steve for an answer to this and post result here.

 

[kthackst]

I have been doing some work on this but do to selling a car it was the next guys problem. The 98-99 have an extra evap solenoid as mentioned above the second on is right next to the charcoal canister. On a 98-99 the charcoal canister is in the driver side of the front bumper under the abs. This extra solenoid missing is what's causing your issue. From doing a pin check pin 55 is where the extra solenoid needs to go.

However the one part I did not finish was there is a difference between the firewall evap solenoid. The 98-99 is actually located on the back of the engine above the ac compressor. The difference is definately physical but I don't know if it reads different. I have yet to try it.

To sum it up.
-Add the second evap solenoid into pin 55.
-Might need to swap firewall evap solenoid to 98-99 version.

 

[fantom73088]

Thanks for all the info. Does anyone know where I can get the pin outs for the 97 and 99 ECU so I can compare them side by side?

Thanks, Adam

 

[luv2rallye]

The pinouts are going to be the same. However I expect the 99 will occasionally drive pin 55 expecting a certain current to flow (for the evap solenoid) to know it's there where the 97 won't drive pin 55 at all. You might get away with putting ANY solenoid on pin 55 just to fool the 99 ECU into thinking the evap one is there (otherwise I suspect an evap CEL such as p0442, p0446, or p0455).

OR... the ECU might not be that sophisticated (to sense solenoid current) and it won't set any CEL as long as the evap test doesn't detect any leaks. You won't know until you try it and drive 100 miles which is the max interval before doing the evap test.

Again tuner Steve is probably more knowledgable on this. Pm him to look at this thread.

 

[SohcBigTurbo]

should work

 

[kthackst]

The pinouts are going to be the same. However I expect the 99 will occasionally drive pin 55 expecting a certain current to flow (for the evap solenoid) to know it's there where the 97 won't drive pin 55 at all. You might get away with putting ANY solenoid on pin 55 just to fool the 99 ECU into thinking the evap one is there (otherwise I suspect an evap CEL such as p0442, p0446, or p0455).

OR... the ECU might not be that sophisticated (to sense solenoid current) and it won't set any CEL as long as the evap test doesn't detect any leaks. You won't know until you try it and drive 100 miles which is the max interval before doing the evap test.

Again tuner Steve is probably more knowledgable on this. Pm him to look at this thread.

Simply put the 98-98 ecu WILL make a CEL if the 98-99 2nd evap solenoid is missing.

I do not know if any solenoid will work. I will check this out soon since my car should be running in about two weeks!!! So fvcking excited!!!!!

 

[azdave]

This is one of many old threads I found that kind of left things unanswered about adding an EVAP emission ventilation solenoid when installing a 98-99 ECU in a pre-98 chassis.

I can confirm that when trying to use a 98-99 4G63 ECU in a 97 or earlier chassis that the ECU will indeed look at pin 55 for a solenoid but it will also look at pin 61 to see what the pressure difference is between the inside of the fuel tank and the atmosphere. At one point the ECU will intentionally cause a "leak" in the vapor lines (opening the solenoid) and then read the differential pressure switch to see if the leak is recognized.

Adding the solenoid without also adding the differential pressure switch will be pointless. The two devices work together to check for leaks in the EVAP vapor lines. This is part of the system that also throws a P0446 code if you forget to tighten your gas cap.

 

[reverus]

anyone ever fix this?

 

[bduran1220]

^^^I might have, but I don't know which other EVAP solenoid everyone is talking about. Maybe the one on the firewall next to the EGR SOLENOID....or there's another???
Like all before......
Before my ecu swap I always had to PCV CEL p0442 once in a while and it would go away...problem solved.
Now the infamous ecu 5 monitors not setting to "ready" for the yearly smog was really making me mad.
So I did what many many have done, I did a 99 GSX ecu swap to my 97 GST, all monitors triggered to ready after a short drive....success!!! Until the final trip to the smog station and P0446 CEL WTF

I changed the EVAP Purge Control Valve & EVAP solenoid I added some vacuum hose clamps as a + let's see what happens

 

[luv2rallye]

The "EVAP emission ventilation solenoid" poster 10 is talking about (which the ECU checks for) is only on the 98-99 GST/GSX models. On the GST it is just in front of the fuel tank while on the GSX it is next to the vapor canister (sometimes under LF headlight, other times under battery). Poster 10 has it right about the 98-99 ECU checking for it and the pressure difference inside the tank (using the fuel tank differential pressure sensor also only on the 98-99).

 

[bduran1220]

^^^awesome imma look into that, could those 98/99 EVS be installed on the 97??? Is there a way around it to trick/ foul the 99 ecu if its too complicated???

sorry for so many questions on a dead thread its just I can't find anything anywhere for p0446!!!
If all else fails ECMlink or that nasty TSB for the faulty 97 ecu's

 

[luv2rallye]

It might be difficult to fool the ECU since it probably relies on the fuel tank differential pressure sensor to give it different values based on what it does during the tank pressure test (which looks for vapor leaks). If you just hang the sensor on there connected to the ECU or put in a resistor divider, you're not going to ever get the value to change which the ECU probably demands seeing (otherwise it assumes the sensor isn't working and will give you a cel). The Evap EVS you could probably get away with just connecting to the ECU since it will just check to make sure it activated.

Actually installing a fuel tank differential pressure sensor to make it work properly would be a challege since you'd have to drill a hole in the top of your tank or get a tank which has one. And installing a Evap EVS would require getting all the hoses and other system stuff that supports it. A lot of work to just use a 98/99 ECU. Far easier and probably cheaper to just get a 97 ECU or use ECMlink.

 

[bduran1220]

Yeah that garbage CEL came back, it was worth a shot. -_-

^^^Thanks man!!! That's exactly what I wanted to find out & your right lots of work for stock management isn't worth it. Only evo 8 is better with Evoscan in this case. well that settles it I'm going back to the 97 ecu and tell the smog tech about the TSB,

and secretly save for a link