Renix Sensor Ground Test


The sensor ground circuit affects the CTS, TPS, IAT, MAP, ECU and diagnostic connector grounds. It’s very important and not something to overlook in diagnosing your Renix Jeep as it is common for the harnesses to have poor crimps causing poor grounds. If any or all of the sensors do not have a good ground, the signal the ECU receives from these sensors is inaccurate.

Set your meter to measure Ohms. Be sure the ignition is in the OFF position. 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.Backprobe 2

Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it runs parallel to the valve cover and also near the MAP sensor mounted on the firewall. If you have an 87 or 88 with the C101 connector mounted on the firewall above the brake booster, wiggle it, too.

You want to see as close to 0 ohms of resistance as possible. And when wiggling the harnesses/connectors the resistance value should stay low. If there is a variance in the values when wiggling the wires, you have a poor crimp/connection in the wiring harness or a poor ground at the engine dipstick tube stud.

Refreshing of the dipstick tube connection is covered in Renix Ground Refreshing, and the sensor ground upgrade is covered in Tip #6 – Sensor Ground Upgrade.

On 87 and 88 models, you could have a poor connection at the C101 connector as well. See Tip #2 – C101 Refreshing and Tip #27 – C101 Elimination.

Revised 1-31-2016

20 thoughts on “Renix Sensor Ground Test”

  1. Hi cruiser54, amazing site! My XJ and I wish we discovered this a long time ago 🙂

    Sorry to message you here, but I don’t see anywhere on this website where to message you directly, other than post replies.

    I’d like to private message you, so can you please reply to my email address, and I’ll write you back?

      1. Cruiser54, I sent you a email hoping you can find the time to read it and hopefully lend me some help with my issue. Thanks

        1. I believe I responded via my private email account. My apologies to all. This site and my private email are supposed to notify me of your responses. They do most of the time, but some replies seem to fall through the cracks.

  2. Ever get into something without actually looking at all components. The previous owners of my 88 XJ apparently found it more convenient to just splice all the wiring together and cut connectors completely out of harness for the TPS. So which wire is it that I should put my positive lead on for this.

  3. hello cruiser 54 jerry here, ( old tools new problem )We.. I completed 1-5 and whill I pull 0 ohms from the neg batt post to the ground lug at the dip stick ( note batt ground hooked up there aswell ) and 0 ohms at the firewall ground lug I get 10 to 19 ohms at the tps,cps, and map sensors
    any input would be helpful.. Thank you.

  4. From tps to battery I have1.6 ohms redid 2 factory splices and took wire out of c101 still 1.6ohms. Pulled computer 0ohms from tps to computer. Only way i can get ohms to change is by removing the grounds at dipstick makes it drop to 0.0 not ofl what am I missing?

  5. Hi cruiser.
    Do you know where I can find a writeup on how to test resistance of the o2 sensor wires for the 90 renix? Being somewhat electrically illiterate I want to be sure I dont damage the circuit.

    Thanks in advance.

  6. That test is done with the sensor unplugged and between the red and black wires. Should have 8 ohms or less. That’s the circuit for the sensor heater.

  7. 90 Wrangler 2.5 MT – With regards to the O2 harness connector when unplugged. I have 3 wires. 12.2 volts to the heavy yellow wire, 0.01 ohms resistance to the ground wire to negative terminal, and an orange wire that I’ve traced back to connection 35 on the ECM connector -No Votage (key on engine off) 0.01 ohms resistance between connector and ECM. I should be getting 5 volts from the ECM on that wire shouldn’t I? If so does that indicate a bad ECM?

  8. Hey bud I did the c101 delete plus a bunch of upgraded grounds you recommend and the old girl still runs like crud. (rough low idle, rich fuel smell that will nearly choke you out at a light) I get a short to ground somewhere when I wiggle the harness on the driver’s side (near the firewall over by the old c101) with my meter (fluke 374fc) I’ve had the jeep for a while but the guy before me couldn’t figure out why it was running this way and he replaced a bunch parts I guess. The map and tube all look new and seem to be doing their duty.

  9. I have a 1990 Comanche auto 4wd that has high idle when warm. It runs good otherwise. When I pull vacuum line off of Map sensor it idles perfectly. Any ideas?

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