jeep.kevin

1989 cherokee. does anybody know if it is possible to reset the main computer?

nasonguy

disconnect the battery cables and touch them together for 30 seconds.

This will clear all the learned programs and trouble codes and anything else like that (such as radio presets and stuff).

Or since I might get yelled at for suggesting touching the two cables together, disconnect the battery cables, and let them sit for half and hour, then reconnect...

Either one discarges the computer entirely.

troy fritz

Absolutely do not touch the cables together. Disconnect the neg battery cable for 5 min, then reconnect. That will clear everything. Or, go to Auto Zone and they will clear it for free and you wont have to reset your clock and presets on radio.

89Laredo

you guys failed to realize its an 89... There are no "trouble codes" stored on the computer, you also cannot go to "the zone" and get it "cleared" (all it does is turn off the CEL until the code is thrown again) because it is PRE-OBD aka no underdash computer connection... Most autozones will only read the codes, they wont delete them anyway. Easiest way would be to disconnect the battery cables and let the capacitors in the computer drain, or touch them together if you dont want to wait... this will remove the stored information in your computer, You have to drive (i think) like 50 miles or 20 minutes for the computer to "re-learn" the fuel mapping, etc for efficient running. If you still have problems after this, try to get ahold of 5-90 he is one of the RENIX gurus on here and should be able to help you...

BlueXJ

What Defiance says is absolutely correct. Why are you wanting to clear the accumulated knowledge in the computer anyway? The Renix computer is not at all like the H.O. stuff's computer. No stored codes. Just an operating system which only has parameters, not functions.

nasonguy

Hehe, I knew I was going to get yelled at.

I was just feeling a little too lazy to explain about the caps in the computer storing energy for a few minutes and stuff like that.

But Defiance did that for me VVVVVV Thanks!!!

89Laredo

Youre welcome, although I dont absolutely recommend touching them together.. Ive seen it done and never really seen any damage done from it, but I HAVE heard of it damaging the computer... But, if someone is too lazy to wait 5 mins thats a chance they can take..

Blue, I dont know how I forgot about you.. 5-90 was the first one to come to mind...

jeep.kevin

the only reason why i ask is im having an stange and yes i do mean strange starting problem. sometimes my jeep takes ten mins to start up and other times it cranks right up like it is brand new. due to recent dicoverys i noticed my distributor mount was loose and just wobbling there, i know that may have jacked up my timming, could that possibly be causing this starting problem?

nasonguy

Yeah, if anything, resetting the computer will only hide the problem for a little bit.

But really, I don't think your computer has anything to do with this.

check your sensors, check grounds, the TPS (Throttle Position Sensor) a lot of times make a vehicle do weird weird things when it fails...

TPS and CPS (Crank Position Sensor) both have to do with starting...

jeep.kevin

what about my coil pack? and also where is the CPS and how do u properly install the TPS?

hypedonmonster

Sonicelectronix also gives you a free dash install kit with a wire harness and a plastic cage mount to keep the factory look

hypedonmonster

Woops wrong post

cruiser54

Renix resets every time you turn the key to OFF. It ain't the OPs problem.

Kevin, start with this:

Renix CPS Testing and Adjusting
　
　
Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out it’s mounting holes with the first drill bit that just won’t fit through the original holes. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
　
Revised 11-29-2011

cruiser54

Here's how to adjust/test the TPS but that isn't the core issue here.


RENIX TPS ADJUSTMENT
Before attempting to adjust your TPS be sure the throttle body has been recently cleaned. It's especially important that the edges of the throttle butterfly are free of any carbon build-up.
IMPORTANT NOTE: Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS. The letters are embossed on the connector itself. Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it parallels the valve cover and also over near the MAP sensor on the firewall. If you see more than 1 ohm of resistance, or fluctuation in your ohms reading, some modifications to the sensor ground harness will be necessary. The harness repair must be performed before proceeding. I can provide an instruction sheet for that if needed.
MANUAL TRANSMISSION: RENIX manual transmission equipped XJs have a three-wire TPS mounted on the throttle body. This manual transmission vehicle TPS provides data input to the ECU. The manual transmission TPS has three wires in the connector and they're clearly embossed with the letters A, B, and C. Wire "A" is positive. Wire "B" is ground. Key ON, measure voltage from "A" positive to "B" ground by back-probing the connectors. Note the voltage reading--this is your REFERENCE voltage. Key ON, back-probe the connector at wires "B" and "C". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For example: 4.82 volts X .17=.82 volts. Adjust the TPS until you
have achieved this percentage. If you can't achieve the correct output voltage replace the TPS and start over.
AUTOMATIC TRANSMISSION: RENIX automatic transmission equipped XJs has a TPS with two connectors. There is a flat three-wire connector, same as the manual transmission vehicles have, and it is tested the same as the manual transmission equipped vehicles—
FOR ENGINE MANAGEMENT RELATED ISSUES. However, the automatic TPS also has a square four-wire connector clearly embossed with the letters A,B,C, and D. It only uses three wires and provides information to the Transmission Control Module. Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your REFERENCE voltage. Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage. For example 4.8 volts X .83=3.98 volts. Adjust the TPS until you have achieved this percentage. If you can't, replace the TPS and start over. So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and the other side feeds the TCU.
FOR AUTOMATIC TRANSMISSION RELATED ISSUES. Check the four-wire connector side of the TPS.
If you have ENGINE issues check the three-wire connector side of the TPS. For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.
Revised 04-30-2012

cruiser54

As to the coil, do this:

Renix Jeep ICU/Coil contact refreshing
　
　
The contacts between the coil and the ICU on your Renix Jeep can become corroded and loose causing a complete or intermittent no-start condition. I recommend the following procedure as a maintenance precaution to insure this is eliminated as a possible cause now and in the future.
The coil is attached to the ICU by two T20 Torx bolts. Remove these two bolts and lift the coil up off the ICU. You will see 2 pins and 2 sets of contacts. Clean both the pins and springy contact pieces with a good electronics cleaner.
Squeeze the springy contacts closer together with some needlenose pliers. Apply some dielectric grease to the contacts and bolt the coil back on to the ICU.
While you’re right there unplug the connectors from the ICU and inspect the pins in the harness connector. Make sure the pins are not retracted into the connector. Spray out the connector and the receptacle of the ICU with the same good electronics cleaner you used earlier. Apply dielectric grease to the connectors and plug them back in.
I feel this procedure should be performed at least once in the lifetime of a Renix Jeep.
　
Revised 11-29-2011