RENIX - Volatile Memory - Discussion Only

[Ωhm]

No better place then here, to throw this question on the chopping block. Does RENIX Engine Control Units (ECU) use Volatile Memory? Myself, I think YES.

 

Following are three (3) reasons why:
1) RENIX ECU has "Hot at all times" (C201_B7) circuit. WHY?
2) If ECU doesn't know Closed Throttle (CT) percentage, what happens during the next START, when someone has their fat foot pushing down on the gas pedal. Will that become the new CT percentage?
3) Does Long Term Fuel Trim (LTFT) really just stand for Next Term Fuel Trim (NTFT)? I don't think so. If that was the case, you'd only need Short Term Fuel Trim (STFT).

 

Now are all ECU's created equal (early ECU's vs later ECU's)? As new strategies and improvements came along during the RENIX years, they were incorporated into the ECU's. Could this be the reason why some say YES to "volatile memory", while others say NO? So this is a good time to sharpen up your butcher knife and start swinging away.

[87MJTIM]

There must be some stored memory in the Renix ECU. when I start my truck, the REM shows the previous LTFT.  It doesn’t reset to 128

[Ωhm]

What year is your ECU?

[87MJTIM]

Came from a 90 XJ with a MT

[Kjell]

Ωhm nice topic . After  fixing my truck and going over every inch of the electric system engin, sensors,  and injectors to ECU i agree with you Ωhm, the ECU has some kind of memory

Most times when working on the electric system i disconnect the battery but i forgett this from time to time and if i fix/replace test something whit battery connected

for exampel changing the heat relay and fix connection to O2 sensor the Renix stays in OPEN LOOP/ runs ruff until i disconnect  /reconnect the battery.

Turning of on ignition with the key makes no difference.

 

I'm 100 % sure the Renix has a memory as long as the ECU has power on B7 connection.  And my guess is it have memory even when it has no power and maby replace some of it  with new data at next startup/run if no error accures.

[87MJTIM]

Page 85 of the Renix Fuel Injection Manual describes a KAM (Keep Alive Memory) that the ECU store with the key off.  However, the LTFT is not mentioned as stored in the KAM.  Maybe the combination of sensors stored in KAM default to keep the LTFT settings.  Sensors stored: O2, MAP, TPS, MAT, and ECT.

[Kjell]

Great 87MJTIM!  why didnt i look closer at that page earlier, must have stucked on the ECU connection page.

Have to print out the manual to get a better overview

On page 86 it says KAM Memory ,something about Average learned closed throttle value CATV and Min /Current / Max sensor values over time  (used for road test/ wiggling cables)

 

Also read that Fault codes are stored in memory as long as the problem is present .They will be deleted after a pre-programmed number of engin starts if  not detected again.

 

Thanks 87MJTIM think we safely could say the ECU  definitely have a memory 

 

Now i can concentrate fixing the Truck instead of translating Swedish thoughts in to English technical words

 

 

[Ωhm]

1 hour ago, Kjell said:

Also read that Fault codes are stored in memory as long as the problem is present .They will be deleted after a pre-programmed number of engin starts if  not detected again.

 

Fault Codes or Diagnostic Trouble Codes (DTC) never made it onboard with RENIX. The intent was there, as shown in the 4.0L Multi-Point Fuel Injection (MPI) manual (printed a year or two earlier), but the ability to read and store DTC's never made it to production. DTC's made their appearance with the Single Board Engine Controller (SBEC) on the 4.0L HO.

[omega_rugal]

if i could read the names of those chips we could figure this out

[eaglescout526]

Well I do see two Motorola chips and a Texas Instruments chip but I can't see their numbers.

[Kjell]

6 hours ago, Ωhm said:

 

Fault Codes or Diagnostic Trouble Codes (DTC) never made it onboard with RENIX. The intent was there, as shown in the 4.0L Multi-Point Fuel Injection (MPI) manual (printed a year or two earlier), but the ability to read and store DTC's never made it to production. DTC's made their appearance with the Single Board Engine Controller (SBEC) on the 4.0L HO.

My ECU came out of a XJ 89, some PO changed it . on the ECU someone have writtten the registration number of the xj and a fault code 1220 and that it appears when the ECU gets Warm.

Found a pdf on Cherokee forum whit codes for Renix saying that code 1220 is  no voltage from EGR solenoid to ECU . 

 

[Ωhm]

12 hours ago, Kjell said:

Found a pdf on Cherokee forum whit codes for Renix saying that code 1220 is  no voltage from EGR solenoid to ECU .

 

Kjell, I doubt very much that this ECU could set a DTC.

[Kjell]

13 minutes ago, Ωhm said:

 

Kjell, I doubt very much that your ECU set a DTC.

I have no idea if it did  

I have a overheated 3 legged thingy ( transistor maby?)on the ECU board ,my guess is that one of the in or output has or had  a fault /short circuit.

 

Everything runs great the only things i'm not sure works are the KNOCK SENSOR can't measure if it work and EGR valve, deleted the EGR valve  i have the HO intake manifold whit no hole for it.

 

Ok ...Facts.. i now there is an error in the ECU , it could be the EGR ,someone has written a note on the ECU saying D1220 appears when it gets warm,

found this pre 91 codes on Cherokee forum Code 1220-No voltage at ECU from EGR solenoid.      LINK (https://www.cherokeeforum.com/f2/diagnostic-code-list-78108/)  

 

I can't see any reason why someone will write D1220  on the ECU and registration number of a 89 xj just for the fun of it .

 

Maybe the codes are in the upgraded version of the  89-90 ECU but Chrysler did now the the odb I was going to replace the Renix and saw no reason to get them out ??

And someone whit Volvo Renault Bendix scan tool here in Sweden did get the D1220 code out of my ECU??

 

 

Anyway interesting topic A pic of my ECU  MNE321(number-plate number) D1220 när ECU:n blir varm (when ECU gets warm)

 

[Ωhm]

Could be what I'm saying is US market only. International stuff is a whole new world to me.

 

On that blown transistor???, is it possible to trace the circuits and determine if one of the legs (transistor) goes to the ECU connectors? Knowing which ECU harness PIN_NUMBER could help in knowing which vehicle circuit is effected.
 

[Kjell]

14 minutes ago, Ωhm said:

Could be what I'm saying is US market only. International stuff is a whole new world to me.

 

On that blown transistor???, is it possible to trace the circuits and determine if one of the legs (transistor) goes to the ECU connectors? Knowing which ECU harness PIN_NUMBER could help in knowing which vehicle circuit is effected.
 

I'm pretty sure there is no special export stuff on the JEEPS for Sweden market accept what the dealer here put on it like ugly turn signals and stuff.

 

 

I'll have a closer look at it!  I had the same idea as you but it doesn't run strait to the connector and it's mounted almost in the middle of the board.  you can see them on the pic above 16 of them mounted in pairs and they are brown on top. I will take some more pics tomorrow , the ECU is back in the Truck now.

Can take some close ups on the E-proms to

[Ωhm]

Gotta love the internet. Not sure, but is this similar or exactly to yours? Might help.

 

 

 

 

[Kjell]

6 hours ago, Ωhm said:

Gotta love the internet. Not sure, but is this similar or exactly to yours? Might help.

 

 

 

 

Thats crazy! LOL  . Fantastic Ωhm 

 

AND guess what, its the EGR canister =A10  

It's the curcit from RelayA/A to Egr canisterthat was overheated i put in a small cable on the back of the board instead, i made a wild guess it was the power supply to the transistor that was bad and not the thingy itself  if it works when cold...

 

Hmm the one to the right at the bottom row  says +5 volt to memory if my order a beer in Spanish skills are right...

 

Do not see anyone say +5 vdc to DTC fault codes do you have more pics Ωhm ? 

 

Ok I'm pretty sure someone got the code 1220 out of that thingy, wonder what they used to get it out .. The truck has been around my neighborhood since 1993  got to do some Sherlock Holms stuff can't bee that many that could have done it, to bad it probably was at least 20 years ago

 

[NickInTimeFilms]

As per request, I have been summoned 

So, seems you guys stumbled onto the Renix MPFI manual and found the KAM page so that's good.
The biggest things I've noticed it saving are the LTFT so it can adjust the fuel map quicker in closed loop, as well as TPS closed position as most users complain of a high idle if they adjust the TPS and don't reset the ECU.

I would like to find out if that sensor key cycle info is accessible in the data stream, but hopes are low. Something I DID find though are some Key-On Self Test bytes which indicate if tests have been run as well as the outcome. So far I've only had time to probe out Injector open faults, but I'm hoping there are more hiding in there. Have a peak! https://nickintimedesign.com/renix-4l-ecu-datastream/

As for those DTC's reported above, correctly assumed they aren't thrown by the ECU, but rather by the scanner. The mystical MS1700 directly probes all wires available in the diagnostic block and can throw all kinds of codes for voltages not being present at appropriate times. Shame they are rare as all hell and clunky at best to use, but certainly a lot to learn from them.

As for the issue at hand, if that power transistor is getting hot, it's possible it's slowly internally shorting and will eventually blow if left unchecked if it's anything like the Injector Drivers. Probably fine with just swapping it out for a new one and see how it does. I can't seem to find the part numbers in my cluster of notes though... so good luck on that hunt.

[Kjell]

12 minutes ago, NickInTimeFilms said:

As per request, I have been summoned 

So, seems you guys stumbled onto the Renix MPFI manual and found the KAM page so that's good.
The biggest things I've noticed it saving are the LTFT so it can adjust the fuel map quicker in closed loop, as well as TPS closed position as most users complain of a high idle if they adjust the TPS and don't reset the ECU.

I would like to find out if that sensor key cycle info is accessible in the data stream, but hopes are low. Something I DID find though are some Key-On Self Test bytes which indicate if tests have been run as well as the outcome. So far I've only had time to probe out Injector open faults, but I'm hoping there are more hiding in there. Have a peak! https://nickintimedesign.com/renix-4l-ecu-datastream/

As for those DTC's reported above, correctly assumed they aren't thrown by the ECU, but rather by the scanner. The mystical MS1700 directly probes all wires available in the diagnostic block and can throw all kinds of codes for voltages not being present at appropriate times. Shame they are rare as all hell and clunky at best to use, but certainly a lot to learn from them.

As for the issue at hand, if that power transistor is getting hot, it's possible it's slowly internally shorting and will eventually blow if left unchecked if it's anything like the Injector Drivers. Probably fine with just swapping it out for a new one and see how it does. I can't seem to find the part numbers in my cluster of notes though... so good luck on that hunt.

Thanks Nick!

Suspected you would have figured out the most of the wrinkles in this French brain!

I'll swap that Power transistor next time i poke around in there... have a bad pic of it .Number on it are  827  and 114-08

 

Whats the right way to reset the ECU would it reset disconnecting/reconnecting + on the battery ?

[Ωhm]

Took myself a journey deep down into the dungeon. Found 1989 Medallion (RENIX/MS1700) diagnostic manual used for Engine Controls, Passive Restraints and MB/MJ Transmissions. Sure enough, all Engine Controlled DTC's are listed as a four digit number generated by the MS1700 tester. No listing for 1220 on the Medallion. Maybe someone has a diagnostic manual for Jeep Engine Controls (RENIX/MS1700)? Medallion manual was printed for Jeep/Eagle dealerships.

[Kjell]

Found  lists of DTC's on different locations on the internet claiming to be for pre 91 / RENIX but not a word of what created them or how.

All have 4 digits ,guess that someone copied them from a manual in the beginning.

It's bad that the scanner  create the DTC  not the ECU ,not much use for the code list whit out the scanner

Think i'll bay the REM from Nickintimedesign and find out if the knocksensor is working and for troubleshooting, instead of hunting down a MS1700.

 

Thanks Ωhm !

Found out lot of interesting stuff so far,it will keep the MJ , Renix running 

 

 

[87MJTIM]

👍👍 for Nicks REM

[Lxs]

  anybody out there got any custom mods for wiring in indicator led for things like signal pulse to fuel inj and a manual kill switch for fuel sys( inj signal& pump)

[cruiser54]

Nick's REM engine monitor does more than the factory scan tool. I have them both.

Do yourselves a favor and visit Nick's website and think hard about purchasing one of his Renix Engine Monitors.  https://nickintimedesign.com/

[NickInTimeFilms]

15 hours ago, Lxs said:

  anybody out there got any custom mods for wiring in indicator led for things like signal pulse to fuel inj and a manual kill switch for fuel sys( inj signal& pump)

I have a benchtop ECU setup with LEDs on each output. It's kinda neat to see, but only mildly useful in very specific use cases. Also lots of wiring cutting involved.
https://www.facebook.com/nickintimefilms/photos/pcb.3515765801820634/3515668145163733

https://www.instagram.com/p/CGJ-GheDbV4/

 

Also, good luck even seeing the injector pulses unless you plan on using a slow motion camera.

Scan tool is going to give you a lot more tangible information, but I'm in the middle of a chip shortage and working on ways around it in the meantime.



As for an injector kill switch, all the Injectors share a common ground so that would be easy to interrupt.