Renix closed/open loop test.
 

I wonder if there is a way for a bonehead in a hurry to stick a meter on his 90 4.0 and see if it is even thinking about what it's doing. Might there be one easy to reach terminal that is one way in open and another closed? (If I have a light I don't know where it is or if it's on or off).

Also, in open loop besides running rich, what's going on with the timing? Thanks in advance, Don.

Bump.

Is there a ALDL plug-in port under the dash for a scan tool/code reader?

There is what I assume to be a test port on the right hand fender, (W/yellow cap/cover.

The renix doesnt really have a test port that you can plug something into to test. I think back in the day the jeep dealerships had a special scanner to test, but I dont think its readily available anywhere now. For testing sensors you need to use a multimeter. To check for an open or closed loop system you will have to ground the o2 sensor and see if it is running rough. If the engine runs rough then it is in closed loop. In open loop the grounding of the o2 should have zero affect on the engine.

Hey, thanks...It's getting 15 instead of the 18-20 I once saw, but seems to run well enough. (that's why my query). I'll try grounding the O2...Thanks again. Don.

You got a PM sir.

Well....I looked at it. It's the hot dirty looking thing, right? (Kidding). o2 wires are too much to deal with right now. Don't have my ramps and don't want to get greasy. (today). I could see it, and I remember putting it in about 9 years ago. (TWO WIRES). I'll save/pick-up this thread for when I get to it. Thanks, Don.

Hey slick, any slick ideas?

There is a port for a drbII reader. Good luck getting one. At least 1000$ if you find one. Luckily we can do the same thing with a multimeter.... saving yours truly a ton of money, and allowing me to make that much more

Whatcha lookin at me for?lol you trying to test the sensors or what? ..... Ive been searching for a list of pins and proper readings for the plugs to no avail.

Well, don't hurt yourself! Sam's idea should work? I'm just to lazy right now. Thought is might be easy just to see if it's open or closed for starters. I did save Eco Mikes O2 test for when I have time. Maybe I'll wait till April!

Ya..... how can you ground the o2? Just wondering.... unplug the harness and ground.... what? Input?

As I remember both wires are black...that was a long time ago. Guess one is the heater and one is the 5v from PCU? Guess ground the 5V and see what changes? By the By, would you know what timing does in open vs closed...that might be an easy way to get a peek at what it's thinking.

Yea, with it unplugged.

Not sure. Guess I just trust the ecu. I have heard of grounding the o2 before but never done it therefore can't tell ya how. I would imagine you ground the center wire as I believe one outside is ground the other is input. I get 9 or 10 volts if I remember right. Anyhow the center wire should be output to ecu. Makes sense cause in open loop you're using preset parameters and closed its relying on the readings. I'm not sure if the timing changes. All I know is my o2 is good and my map is bad....... causing a rich condition. New map will be here Tuesday :cheers: