Negative. Jeeps built 1987-1990 have a Renault-Bendix (Renix) emissions control system that does not throw codes or provide diagnostic output. There is no check engine light on these vehicles unless the dash or instrument panel were swapped by a previous owner, and even then the ECU would not tell a CEL to come on. The ECU (emissions control unit) is very simple and is pre-OBD1, it cannot detect an error from the engine's sensors. The emissions testing center you (the OP) are taking it to should know this, but if you have to humor them just wire it to another light that comes on when you turn the key, as BustedBack mentioned.

The only diagnostic tool available for an '87-90 XJ is a DRB II scan tool with a Jeep adapter, which simply checks for current return from sensors and actuates the IAC motor. It can be used to adjust the idle in this manner. These plug into the D-pins near the relays on the passenger side of the engine bay, usually covered by yellow rubber caps.

 

why is there diag conn by relays by prtessure bottle they are the yellow conn in pic

 

I was editing my post as you asked that question, sorry for the delay.

 

see themthose are diagnostic ports

 

Bingo.

Alternatively you can adjust the IAC motor by plugging 12 volts into the larger diagnostic connector. The socket in the middle closest to you will retract the pintle, the one just above it will advance it. If you get it wrong you can fry some things though, so be careful doing this.

I think Snap-On makes an adapter as well, and I've heard 5-90 on here is reverse-engineering a scanner to work with those connectors.

 

Its strange to hear you break down ECU into emissions control unit. DSMs use the same acronym, but it breaks down as Engine Control Unit. And believe me, its not just controlling emissions!

 

ty all for helping me . think i found the problem its the CPS crankshaft position sensor . i just have to figure out how to get it out and what tool to use


bcingu

 

the cps ha snothing to do with the check engine light you dont have one you never did just like mt truck you are going to waist money do you have these connectors under you hood by the batteryif so you do not have a provision for a check engine light go to the chrylser dealer ship and le them loo it up

 

no i havent but ty

 

oh i read the posts thank you , i already bought the CPS i had to mine was frayed and it wont stay started it dies when i drive it now . it says that it tells the computer what to do so i think it will help . i just dont know how to get it out or what tool to use its so far down and close to the back not alot of room to get a tool down there .

 

jack up truck support with jack stands go from underneath its either 10 mmor 11mm i think need long extensions a couple of them

 

is your motor a v6 or 4.o inline 6

 

V6

 

from the book v6s do have a check engine light his profile says v6 but this post says 6cy you jump these two terminals to activate codes we all learned some thing today

 

so look for the check engine light on the information center on left of steerin wheel and change bulb if you have a v6