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  #151  
Old January 29th, 2019, 13:24
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Ecomike Ecomike is offline
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Re: Testing Jeep O2, Oxygen sensors

You do know that Nick (nickintimevideos youtube and facebook...) has already built something like 100 Renix ECU scanners ( REMs ) in multiple versions the last 18-24 months right? We have a group of over 1000 renix owners now on the facebook page. Very active. I have been referring many questions over there to over here where we have indexing, searchable FAQs and threads like this one.

He is using open source code .....

Quote:
Originally Posted by kastein View Post
I and a few other /ECU tuning guys are working on reverse engineering the entire RENIX ECU (both hardware and software) but we haven't touched the 2.5 one yet. It is very different from the 4.0L one, TBI vs MPFI, only one MCU instead of two on the PCB, etc.

I do have a spare 1990 2.5 manual ECU but I need it for our project and it sounds like the ECU is probably not the problem here.
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  #152  
Old January 29th, 2019, 14:56
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Re: Testing Jeep O2, Oxygen sensors

Yeah, but we're looking to reverse engineer the firmware and hardware of the ECU. Basically attack the problem from the other end of what he's doing. What we know so far - combination of my work and others -
- the ECU contains two MC6801 chips on 4.0L, each with its own 4kB onboard mask ROM which cannot be modified after manufacture
- it also contains 2kB of SRAM and 8kB of EPROM storage that are used by the main MC6801 for engine and vehicle specific firmware and data storage
- one 6801 is dedicated to realtime operation of important engine subsystems, the other controls overall EFI strategy, peripherals, and comms
- I think I've already posted the info I have on the ECU connector part numbers.

I can't really give much more info as we are still working on it and I haven't had time to poke at it in a week or two now, but I'm approximately 1/4 of the way through disassembling the main MC6801's onboard mask ROM contents by hand. So far it looks like the reset handler and I/O configuration/setup and I'm 99% sure the part I'm working through at present is the serial comms handler.

My hope is to help answer any unanswered questions as to what sections of the serial comms output data means for the REM project and ideally improve RENIX tuning availability, though it will almost certainly require ECU modification as the 8kB EPROM is an OTP type (One Time Programmable) which means it will have to be desoldered and replaced with a socket or EEPROM device on any ECU that is to be tuned. There is a tiny chance that the 2kB SRAM can be used for small amounts of tuning patch code... but don't cross your fingers. I would like to crack this thing wide open and allow full tuning (HONDATA style - mod your ECU hardware, write whatever tune you want to it) and possibly add better diagnostics features to the ECU, for example broken sensor/wire detection, stored codes, etc etc. The ECU only has 32 bytes of nonvolatile RAM and I'm not sure how much of it is used by the existing codebase, so stored codes may be an impossible pipe dream, though I haven't found any use of the nonvolatile address range yet.

I won't speculate further until we have more solid information, and I'd like to thank Mark Nelson and Chris from Christuned for the opportunity to help work on this. Last time I got to reverse engineer something like this was far too long ago, it's fun.

Quote:
Originally Posted by NickInTimeFilms View Post
That. sounds. awesome! I'd love to chat sometime about your work if you're interested. I've been doing tons of work decoding the data streams lately, but I'd love to know what else is hiding in those chips.
Would love to discuss it once we have better data. The last thing I want to do is mislead anyone with preliminary information that may be entirely wrong.
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  #153  
Old January 29th, 2019, 18:43
Cwburrell Cwburrell is offline
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Re: Testing Jeep O2, Oxygen sensors

Quote:
Originally Posted by Ecomike View Post
Good news!!!

The 86-90 XJ, 2.5L, 4 banger, seems to have been a throttle body injection system (it is not multi-port injection) using the other style O2 sensors, the ones that generate there own voltage, 0-1 volt. The ECU does not feed a voltage to the O2 sensor on the 2.5 Liter per Nick, and I seem to vaguely recall hearing this about the 86 four banger and he looked it up in the manual.

So your ECU may be OK!!!! Your O2 sensor may be bad, or may even be the wrong type????

So tell us the whole story on your rig, new sensor? Part number and source? Did they sell you 4.0 sensor by mistake?

The test method for your O2 sensor will be the same as for the 91-01 HO 4.0's.

I actually just purchased this jeep and the previous owner mentioned the hard starting in cold weather. I havenít changed the O2 sensor so I have no idea what is actually in it. Iíll have to dig out my old analog meter and see what the voltage does.
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  #154  
Old January 29th, 2019, 19:14
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Re: Testing Jeep O2, Oxygen sensors

Cold starting with renix is common with old batteries, corroded battery/ground contacts, and low battery cranking voltage. ECU must see 10 volts minimum from the battery at the ECU. Mine needed at least 11.5 or so cranking volts at the battery posts for the engine to turn fast enough for the CPS to produce enough voltage for the ECU to see the crank signal, otherwise the ECU does not wake up and fire spark and inject fuel.

Also today's CPS's are need to be moved closer to the crank shaft to boost the cranking voltage of the CPS. It generates its own voltage, from a permanent magnet at the tip and induction coil. As the teeth and teeth gaps fly by the magnet tip, it induces an EMF force that creates the crank signal. Needs to be at least .50 volts AC to always start. That voltage changes, with cranking rpms, that change with battery condition and engine temp...etc

Quote:
Originally Posted by Cwburrell View Post
I actually just purchased this jeep and the previous owner mentioned the hard starting in cold weather. I havenít changed the O2 sensor so I have no idea what is actually in it. Iíll have to dig out my old analog meter and see what the voltage does.
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  #155  
Old February 6th, 2019, 18:50
Cwburrell Cwburrell is offline
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Re: Testing Jeep O2, Oxygen sensors

Quote:
Originally Posted by Ecomike View Post
Cold starting with renix is common with old batteries, corroded battery/ground contacts, and low battery cranking voltage. ECU must see 10 volts minimum from the battery at the ECU. Mine needed at least 11.5 or so cranking volts at the battery posts for the engine to turn fast enough for the CPS to produce enough voltage for the ECU to see the crank signal, otherwise the ECU does not wake up and fire spark and inject fuel.

Also today's CPS's are need to be moved closer to the crank shaft to boost the cranking voltage of the CPS. It generates its own voltage, from a permanent magnet at the tip and induction coil. As the teeth and teeth gaps fly by the magnet tip, it induces an EMF force that creates the crank signal. Needs to be at least .50 volts AC to always start. That voltage changes, with cranking rpms, that change with battery condition and engine temp...etc
The jeep has a new battery and I even hooked jumper cables to my truck but it didnít change anything. I put my timing light on the number one plug wire so I could observe the spark. It took a few revolutions before the light would blink and then the engine would fire. I measured the voltage coming from the CPS and it was only showing .0-.1 volts while cranking. There is no adjustment on the CPS mount to move it closer to the flywheel. I figured the CPS was bad so I got a new one from NAPA. When I went to move the jeep into my shop it wouldnít start at all so I changed it right where it sits. It still wouldnít fire with the new CPS installed. I measured the voltage coming from the new CPS while cranking and it shows .0 volts. After cranking it numerous times it finally fired. The new CPS acts just like the old one did. Takes a few revolutions to See a spark in the timing light if it starts at all. Iím pulling my hair out over this starting issue.
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  #156  
Old February 7th, 2019, 03:54
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Re: Testing Jeep O2, Oxygen sensors

Not all test meters are super accurate. I have seen 50% + variations in the meter readings for the CPS. First you must use AC not DC setting on the meter. Second the CPS must be disconnected from the harness.

The CPS can be moved closer by drilling the CPS mounting holes to a larger hole size. One drill size larger helps a lot. I found on my 87, that putting a super thin washer between the bell housing and the CPS mounting arm, think 1/32" thick shims doubled my CPS output from .24 (with the larger holes already) to .60 volts AC.

Also I was in a recent chat with someone who we think had dirt/rust stuck in the flywheel spaces (windows if you will) that trigger the CPS signal.

Not sure why you posted on the O2 sensor thread????

Also what year is your rig? Renix 87-90???? If it is newer HO 91-01 the CPS does produce any voltage. The ECU supplies it...

Quote:
Originally Posted by Cwburrell View Post
The jeep has a new battery and I even hooked jumper cables to my truck but it didnít change anything. I put my timing light on the number one plug wire so I could observe the spark. It took a few revolutions before the light would blink and then the engine would fire. I measured the voltage coming from the CPS and it was only showing .0-.1 volts while cranking. There is no adjustment on the CPS mount to move it closer to the flywheel. I figured the CPS was bad so I got a new one from NAPA. When I went to move the jeep into my shop it wouldnít start at all so I changed it right where it sits. It still wouldnít fire with the new CPS installed. I measured the voltage coming from the new CPS while cranking and it shows .0 volts. After cranking it numerous times it finally fired. The new CPS acts just like the old one did. Takes a few revolutions to See a spark in the timing light if it starts at all. Iím pulling my hair out over this starting issue.
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34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091
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  #157  
Old February 7th, 2019, 07:11
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kastein kastein is offline
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Re: Testing Jeep O2, Oxygen sensors

The discrepancy is probably because of true RMS vs non true RMS and/or sample rate. Cheap meters typically use lower sample rates and non true RMS (they assume the signal is a perfect sine, read the peak voltage and multiple by square root of 2 to get volts RMS) while a good meter will have a higher sample rate and true RMS which will give you a different answer from true RMS if the signal is not a perfect 50 or 60hz sine wave.

It may also be input impedance related, though even the cheapest meters are typically at least 1 megohm input impedance these days and shouldn't be loading the CPS signal down at all.
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  #158  
Old February 7th, 2019, 09:25
Cwburrell Cwburrell is offline
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Re: Testing Jeep O2, Oxygen sensors

Quote:
Originally Posted by Ecomike View Post
Not all test meters are super accurate. I have seen 50% + variations in the meter readings for the CPS. First you must use AC not DC setting on the meter. Second the CPS must be disconnected from the harness.

The CPS can be moved closer by drilling the CPS mounting holes to a larger hole size. One drill size larger helps a lot. I found on my 87, that putting a super thin washer between the bell housing and the CPS mounting arm, think 1/32" thick shims doubled my CPS output from .24 (with the larger holes already) to .60 volts AC.

Also I was in a recent chat with someone who we think had dirt/rust stuck in the flywheel spaces (windows if you will) that trigger the CPS signal.

Not sure why you posted on the O2 sensor thread????

Also what year is your rig? Renix 87-90???? If it is newer HO 91-01 the CPS does produce any voltage. The ECU supplies it...
I was trying to read it DC so I will go back and try it AC. I also have a better fluke meter that I will use. This jeep is an 89 so the CPS should put out voltage. I originally was thinking this cold starting issue was related to the O2 sensor but Iíve since eliminated that as a cause, but we just kept discussing it on this thread. Thanks for the input.
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  #159  
Old February 8th, 2019, 07:48
Cwburrell Cwburrell is offline
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Re: Testing Jeep O2, Oxygen sensors

Quote:
Originally Posted by Cwburrell View Post
I was trying to read it DC so I will go back and try it AC. I also have a better fluke meter that I will use. This jeep is an 89 so the CPS should put out voltage. I originally was thinking this cold starting issue was related to the O2 sensor but Iíve since eliminated that as a cause, but we just kept discussing it on this thread. Thanks for the input.
I measured the voltage on the CPS AC and it was showing .4 volts. So I did as you mentioned and enlarged the holes in the mount and moved it closer to the flywheel. It started putting out .6 volts which now allows it to fire rather quickly instead of having to crank it for 10 minutes on a cold morning just to get the first fire. But itís still very cold natured. Now it fires quickly but immediately dies. I have to keep doing that 15 or 20 times to get it to stay running. When it does finally get warmed up it seems to run much better so hopefully Iíve made progress. Any tips on how to cure the extremely cold natured starting now?
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  #160  
Old February 9th, 2019, 09:52
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Re: Testing Jeep O2, Oxygen sensors

Well congratulations!!! Well done.

How about we move the remaining cold start question to a new thread? And as you mentioned the O2 sensor is not used in starting or running while cold. ECU ignores it till its warmed up.

Quote:
Originally Posted by Cwburrell View Post
I measured the voltage on the CPS AC and it was showing .4 volts. So I did as you mentioned and enlarged the holes in the mount and moved it closer to the flywheel. It started putting out .6 volts which now allows it to fire rather quickly instead of having to crank it for 10 minutes on a cold morning just to get the first fire. But itís still very cold natured. Now it fires quickly but immediately dies. I have to keep doing that 15 or 20 times to get it to stay running. When it does finally get warmed up it seems to run much better so hopefully Iíve made progress. Any tips on how to cure the extremely cold natured starting now?
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  #161  
Old February 9th, 2019, 21:09
Cwburrell Cwburrell is offline
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Re: Testing Jeep O2, Oxygen sensors

Quote:
Originally Posted by Ecomike View Post
Well congratulations!!! Well done.

How about we move the remaining cold start question to a new thread? And as you mentioned the O2 sensor is not used in starting or running while cold. ECU ignores it till its warmed up.
I greatly appreciate your help Ecomike. Iíve posted a new thread ďextremely cold natured YjĒ.
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  #162  
Old May 9th, 2019, 17:44
randy57 randy57 is offline
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Re: Testing Jeep O2, Oxygen sensors

I introduced a tiny squirt of electronics cleaner into the intake and the engine wanted to quit for a brief moment.
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  #163  
Old May 12th, 2019, 18:20
randy57 randy57 is offline
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Re: Testing Jeep O2, Oxygen sensors

Quote:
Originally Posted by Ecomike View Post
This question comes up a lot in threads with O2 sensor trouble codes and threads about bad mileage. I hope to use this post (thread) as an FAQ about how to properly test mounted jeep O2 sensors and the wiring and related hardware.

For the Renix years, 87-90, the O2 sensor has 3 wires, 2 black and 1 orange. The orange wire (largest gauge of the 3) is the 12-14 volt power that comes from the O2 sensor heater relay on the passenger side firewall, and that powers the internal heater in the sensor so that the sensor can work at idle, and almost immedietly after start up. Loss of that power will hurt gas mileage even with a good O2 sensor.

One of the black wires is a common ground for the heater power and O2 signal to the ECU, so a poor ground will give a voltage feedback from the heater power input, to the ECU causing poor mileage even with a good O2 sensor.

The third wire, also black is a voltage feed wire, 5 volts, from the ECU to the O2 sensor. The O2 sensor is an O2 concentration sensitive variable resistor. At optimal O2 concentration the 5 volt input feed to the O2 sensor drops to 2.45 volts due to losses across the O2 sensor to ground. That same wire if disconnected from the O2 sensor will read 5 volts constant to ground.

At idle that voltage should read 1-4 volts oscillating quickly back and forth roughly once every second. At 2000 rpm it should run between 2 and 3 volts max, and is optimally running between 2.3 and 2.6 volts at 2000 rpm (in park). A digital meter can NOT be used for reading the O2 sensor voltage, but it can be used to test the ground and the 12-14 volts to the heater and the 5 volt feed from the ECU with power on and engine off. You must use an old style analog meter with the needle gauge on the display to see the voltage swing back and forth with the engine runing.

If the O2 sensor readings are not right, say they read 4 volts or 1 volt steady, you have a problem. BUT before you blame the O2 sensor make sure it has good wiring, and make sure the proper voltage is feeding it, by turning power on, engine off to read the engine off voltage feeds (12-14 volts on the orange wire, and 5 volts on one of the two black wires), and ensure the ground wire (power off) reads less than 1 ohm to the battery negative post.

A leaky exhaust system or leaky fuel injector(s), or bad compression, bad rings or leaky valves, bad plugs, wires, cap, rotor, HV coil, and so on, or combination of these, can also cause a lean or rich condition that gives you high or low O2 sensor readings that are not the O2 sensors fault, so try and verify those other items also before buying parts like an O2 sensor to fix your problem.

My next post will be about testing the HO years O2 sensors, as they are a different animal.
Where do you get Orange and two black wires?
The 1990 FSM shows the engine side harness wires as Orange at the (A) on the plug, Black (B) on the plug and Grey (C) on the plug.
Orange going to the oxygen sensor relay, Black going to ground and grey going to D9 computer pin.
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  #164  
Old May 12th, 2019, 18:51
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Ecomike Ecomike is offline
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Re: Testing Jeep O2, Oxygen sensors

Good to know, thanks for sharing. My 87 is black on both. Perhaps AMC was using what wire it in 87, Black, LOL. Or the gray one is black with age, LOL. I used an ohm meter
to sleuth out which was the 5 Volt supply and which was ground.
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  #165  
Old May 12th, 2019, 22:17
randy57 randy57 is offline
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Re: Testing Jeep O2, Oxygen sensors

So that's why you had orange and 2 black.. Too bad they could not have been more consitant. Wouldve made it easier.
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