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  #1  
Old July 20th, 2016, 00:21
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Renix scanner port data question.

Been shopping for a mt2500 for my 89.
While watching vids of them being interfaced with xjs on you tube got me to thinking if it would be possible to read o2 signal data from the ecu with a dvm off of one of the pins in the renix port?(would obviously take some trial and error to find the o2 signal pin from the ecu but there aren't THAT many pins in a renix)
What do ya think?
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  #2  
Old July 20th, 2016, 13:49
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Re: Renix scanner port data question.

The biggest problem is that the signal is a pulsing signal. If your meter isn't fast enough you won't be able to get a reliable signal.

The control circuit does a +/- 1 Lambda control sequence. I monitor my Stochastic ratio on the stroker using a WEGO and you can watch it bounce up and down every second or two.
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Old July 21st, 2016, 00:42
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Re: Renix scanner port data question.

Thanks for the reply.
So the signal at one of those diagnostics pins would be different than using a dvmm directly at the o2 sensors output wire?
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Old July 21st, 2016, 07:42
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Re: Renix scanner port data question.

The MT2500 does not give you a single number. It bounces up and down on the O2. You have to eyeball the numbers and pick the portion of the waveform you care about. It is the same when you do it with a voltmeter but the autoranging on a cheap DVM can cause problems. What I was trying to get at is that with both solutions you do not get a nice smooth number, it is constantly flipping back and forth even with a standard O2 sensor, much less with a WEGO.
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Old July 21st, 2016, 10:51
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Re: Renix scanner port data question.

What you need is a high impedance analog volt meter to read it properly and do it at the sensor in case the wiring is compromised. Not sure yet what the MT-2500 display shows, have not tried mine yet. But if it is a live wave form it should be good for seeing what the signal looks like at the ECU. What the ECU sees, may not be what the O2 sensor data at the sensor is. I would never use a DVM for O2 sensor tests. The data is more like a sin wave.
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Old July 21st, 2016, 11:38
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Re: Renix scanner port data question.

The MT2500 just shows a digital voltage and it jumps back and forth.
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  #7  
Old July 21st, 2016, 23:04
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Re: Renix scanner port data question.

Im gonna get my hands on one of those MT 2500

.
I have a high end dvm and tested the o2 signal last night and its bouncing around from high to low about once a second in closed loop.From my research this confirms that my o2 sensor and ECM
Sensor circuit are both functioning correctly....

Purpose of asking about using diagnostics pin for o2 signal was to have a quick way to check up on o2 sensor function once in a while and not have to mess around under jeep back probing the connector.
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Old July 21st, 2016, 23:15
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Re: Renix scanner port data question.

Problem is however,i looked at the pinout for the scanner ports and the only thing o2 related was heater circuit....what gives?I know the 2500 sees o2 signal at one of these pins?
From the vids ive watched the o2 signal you see on a typical non graphing 2500 scanner is the same you see using a good DVM with high sample rate directly at the o2 signal wire.
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Old July 21st, 2016, 23:21
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Re: Renix scanner port data question.

The MT2500 doesn't read the O2 directly. It gets serial data from the computer (via that diagnostics connector). This data includes all of the sensor readouts including but not limited to O2.
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Old July 22nd, 2016, 08:22
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Re: Renix scanner port data question.

Maybe this will help.




Keep in mind that if you see wildly
fluctuating readings, the sensor is working. When they're bad, the meter would hardly move mush at all and generally is stuck at .1 or 4.9 volts.

Another thing to consider is whether the sensor has power and ground. If you unplug the sensor and check resistance between orange and black, you should have about 8 ohms resistance. If nor, it will generally have no continuity telling you the O2 sensor heater is shot.
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  #11  
Old July 22nd, 2016, 22:14
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Re: Renix scanner port data question.

So the serial data is interpreted by the mt2500......i suspected that when i saw that pin on the pinout...figured it was some digital serial code that the ECU sends to the diagnostics pin and is decoded via scanner into usable data.
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  #12  
Old July 22nd, 2016, 22:19
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Re: Renix scanner port data question.

Ok guess I'll shelf the idea now that i know how things work more clearly.
Ive been on a fact finding mission the past few weeks in search of a better understanding of how jeep computer systems operate.

All began when i started having a intermittent start and immediate stall prob on my other jeep (97 zj)in turn caused me to start testing sensor inputs/outputs on my 89 renix just to satisfy curiosity of how well that system was functioning.
Started de-engineering how ECU systems work to better trouble shoot problems.

Thanks to all who replied.....really helped me have a better understanding of the renix scanner ports.

Last edited by outlander; July 22nd, 2016 at 22:23.
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  #13  
Old July 22nd, 2016, 22:26
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Re: Renix scanner port data question.

Oh almost forgot to ask one final question on the renix system o2 heater circuit....just for my information what causes the ECU to shut off the heater?
Closed loop?
Fuel trims?
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  #14  
Old July 23rd, 2016, 10:03
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Re: Renix scanner port data question.

The O2 heater runs all the time while the engine runs. The sensor gets too cold to work, to read O2 concentration, at idle. Have you read my old file, "The RenX Files" from about 10 years ago and my "How to test O2 sensors" on jeeps thread here? Also I have a new MT-2500 thread this year on the tools forum here. I just bought one about 10 weeks ago. Have not really dived into what all it can tell me yet. I will soon. I had been wanting one for 10 years. I bought the cables and cartridges to test all US rigs up to 2001 and back to the early 80s for about $350 on ebay.

The RenX Files high idle...

http://www.naxja.net/forum/showthread.php?t=905849

Testing Jeep O2 sensors, covers 87-90 and 91-01, which have totally different O2 sensors (and different CPS sensors for that matter)

http://www.naxja.org/forum/showthrea...+sensor+t est
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Last edited by Ecomike; July 23rd, 2016 at 10:08.
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  #15  
Old July 24th, 2016, 02:28
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Re: Renix scanner port data question.

So as long as the engine is running the o2 heater is in operation?
What about key on engine off?should it be on then or only in run?
I will drift through the ren x files thread just for kicks....thanks.
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