getting around OBDII

Elliott

Elliott

Well-Known Member
Joined
Mar 20, 2005
Location
San Diego, CA
Well I currently am working on the wiring for my AW4 swap into my 98 zj. I have done a good bit of research on the swap and found about all I need but am getting stumped on one thing. Since the AW4 uses a seperate control module (instead of the ECU like on OBDII vehicles) my check engine light will be on when the swap is done because it doesn't detect the tranny related sensors.

I'm not an electrical engineer by any means but are there any ways to trick the ECU? Maybe wire in some resistor to make the comp. think the old tranny is still in there? I can't have the CEL on because this thing is a street driven DD and has to pass inspection every year.

Thanks for any insight.
 
BTT. What is involved in switching over to an OBDI system found in 93-95 ZJ's? AW4's were in early ZJ's so that would make the swap a freaking breeze. Thanks.
 
find which sensors the 2 transmissions have in common, you'll have to integrate the newer trans sensors into the old trans some how.

"Just adding a resistor" probably isn't gonna help as the ECU is looking for a pulse/tone value from the sensors.

Backward engineering to an OBD1 system is still not gonna let you pass inspection as you still have to connect to the state OBD2 computer to verifiy VIN and emission info (which OBD1 does not do).
 
Ridgerunner said:
Just thought but can you use a ECU from a manual trans/ that way it won't care about the AW4
Click to expand...

Were ZJ's offered with manual trans ? Would an XJ ECU cross over and integrate with the ZJ system ?
 
Remember seeing this on pbb, did a quick google and heres the link...

http://www.stu-offroad.com/engine/aw-4/aw-4-1.htm

Basically he swaped the AW4, from an XJ into his '97 TJ and its very well documented including all the wiring and ECM stuff.. Not sure if its exactly what you need but its a good read...
 
yea i have extensively read Stu's writeup, its awesome.

The 93,-95 ZJ's actually came with AW4 trannies but they were OBDI and mine is a 98 (OBDII). I'm thinking about Blkvoodoo's idea to just trace down all the wires related to the transmission and wire them in with the stock ECU.
 
there were 5spd ZJs, but they are rare as hell and use a shitty gearbox
 
Elliott said:
yea i have extensively read Stu's writeup, its awesome.
The 93,-95 ZJ's actually came with AW4 trannies but they were OBDI and mine is a 98 (OBDII). I'm thinking about Blkvoodoo's idea to just trace down all the wires related to the transmission and wire them in with the stock ECU.
Click to expand...

yes true but he swaped in a AW4 from from a later 97+ XJ which would be OBDII. Point was that an AW4 DID come on an OBDII Jeep... you could easily swap a chip/PCM and mod the wiring to be similer to that..

You seem to be hung up on the "it must be from a ZJ" thing and I'm not sure whats so different in an XJ or ZJ computer systems ??

I'd start with a FSM of your vehicle and start digging. Many lines on a manual tranny are simply grounded to signal its a manual. Where with an auto they'd interface with the other controler module... Point is it was avaliable on OBDII so the PCM to run it is out there..
 
If all you want is the CEL off--why not go behind the dash and find the wire going to the light and disconnect it---I'm not trying to be a smart a$$ but if getting the light to turn off is all you want---that would be an easy fix. Now if you need it hooked up for the computer that would be different.
---Sty
 
the light has to be operational to pass inspection. if the CEL doesn't come on when the vehicle is first started or with the key on the on position, it immediately fails.

i'm with everyone else that's mentioned swapping to a manual computer. i see no reason why an xj or tj I6 manual computer wouldn't work. in the event you have a 5.2, plenty of dakotas and rams came with 5.2 manuals.
 
Thanks for that bit of info Rufus---I'll have to keep that in mind.
Good luck with the fix--I hate wiring and all the inspection crap---that's why I'm glad mine (1970 Bronco) doesn't need any inspection anymore :) .
And before any of my smart A$$ friends post---I know-I know---my truck doesn't run so why would it need an inspection anyway :flipoff2: .
---Sty
 
HooptyWagn: the check engine light is a great way to diagnose little problems on a vehicle. I could just pull out the bulb (like i did with the ABS) but there are several other diagnostics I need to make sure are operating smoothly.

Yager: Thanks for the insight, those are some good ideas. I'm not really hung up on it having to be from a ZJ, its just the AW4 is from a 96 XJ (OBDI?). I've been reading up on the various wiring diagrams and transmission schematics to see what I need to do for it.

Well good news is I got the 35's mounted up and even more sheetmetal chopped off.
 
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