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Dead on Awsomeness....
great discussion.
great discussion.
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Supposedly, you can read active codes on the 3126 using the check engine light. I believe this is done by closing the cruise control set/accel circuit with the cruise control circuit open/not enabled. Cruise control is native to the 3126 engine ECU. Now wether that feature was enabled on the engines delivered to the military is a question. The pins that need to be jumpered would be accessed in the ECU connectors. Broke overland over on youtube just detailed how to install a cruise control and he shows very well how to access the appropriate pins on the ECU. I do not know if he had to have his ECU programmed to enable cruise control, but he has cruise controlFrom what I have read and understand so far, a code reader is necessary to retrieve engine codes on the 3126 (I'd be delighted to learn that I'm wrong). I read a technical manual for the 3126 that was discussing buses, but what it described for buses was the same on our truck. The manual said that codes can be read out on a 3126 if the vehicle is equipped with cruise control. I do not think LMTVs have cruise control. If they do, mine seems to be missing.Thanks for your insight. I will look into getting a code reader.
Cruise control is in the ECM on the 3126 Adding a simple switch to power it up and put a circuit break off the brake light switch.Supposedly, you can read active codes on the 3126 using the check engine light. I believe this is done by closing the cruise control set/accel circuit with the cruise control circuit open/not enabled. Cruise control is native to the 3126 engine ECU. Now wether that feature was enabled on the engines delivered to the military is a question. The pins that need to be jumpered would be accessed in the ECU connectors. Broke overland over on youtube just detailed how to install a cruise control and he shows very well how to access the appropriate pins on the ECU. I do not know if he had to have his ECU programmed to enable cruise control, but he has cruise controlYou can find the pins on a 3126 ECU wiring diagram as they are listed/labeled. there are also some youtube vids showing guys reading codes in civillian trucks with the cruise switches on their dash...
yes it would be good not to need a code reader out in the boonies. One reason I like the 3116, especially given the 3126 ECU’s track record of just loosing its brain when it’s internal battery craps![]()
.Supposedly, you can read active codes on the 3126 using the check engine light. I believe this is done by closing the cruise control set/accel circuit with the cruise control circuit open/not enabled. Cruise control is native to the 3126 engine ECU. Now wether that feature was enabled on the engines delivered to the military is a question. The pins that need to be jumpered would be accessed in the ECU connectors. Broke overland over on youtube just detailed how to install a cruise control and he shows very well how to access the appropriate pins on the ECU. I do not know if he had to have his ECU programmed to enable cruise control, but he has cruise controlYou can find the pins on a 3126 ECU wiring diagram as they are listed/labeled. there are also some youtube vids showing guys reading codes in civillian trucks with the cruise switches on their dash...
yes it would be good not to need a code reader out in the boonies. One reason I like the 3116, especially given the 3126 ECU’s track record of just loosing its brain when it’s internal battery craps![]()
would assume one would clip in a (for sure charged) aux battery to keep power to the unit while remove old/replace new battery. Though info storage as backup for plethora of purposes would be good. Maybe on old eprom??.
So, I have to ask...
You mentioned "3126 ECU’s track record of just loosing its brain when it’s internal battery craps".
Stupid question I guess - but is there an internal battery (somewhere) that needs to be replaced? On some schedule?
AND if this battery is keeping some electronic component powered with important information...
How do you (we) store that data while the battery is replaced?
.
The battery is not replaceable, that is the problem. You must replace the ECU, and cat will program it based on your engine s/n....
So, I have to ask...
You mentioned "3126 ECU’s track record of just loosing its brain when it’s internal battery craps".
Stupid question I guess - but is there an internal battery (somewhere) that needs to be replaced? On some schedule?
AND if this battery is keeping some electronic component powered with important information...
How do you (we) store that data while the battery is replaced?
.
.would assume one would clip in a (for sure charged) aux battery to keep power to the unit while remove old/replace new battery. Though info storage as backup for plethora of purposes would be good. Maybe on old eprom??
Okay, so does that mean that you should have a new ECU sitting in a sealed box waiting for the day you need it?The battery is not replaceable, that is the problem. You must replace the ECU, and cat will program it based on your engine s/n...
PhooeyThe battery is not replaceable, that is the problem. You must replace the ECU, and cat will program it based on your engine s/n...
Phooey, Yeah like out in the forest that not happeningThe battery is not replaceable, that is the problem. You must replace the ECU, and cat will program it based on your engine s/n...
Is the board potted ? (Sealed in epoxy or ?) I wonder if it could be back fed or tapped in to.The battery is not replaceable, that is the problem. You must replace the ECU, and cat will program it based on your engine s/n...
You could. You could also pre-emptively replace it. I have been dealing with ECU’s for decades now and have never encountered an ECU failure. It supposedly does happen, but I have never personally experienced or heard from anyone who has had an ECU issue, working on a lot of Toyota, Honda and Mitsu... Normally removing power only wipes out stored codes and learned data, not the base program, This is what appears to happen to the cat, as the ECU failures I have read about and helped troubleshoot usually occured after a loss of vehicle battery power.Okay, so does that mean that you should have a new ECU sitting in a sealed box waiting for the day you need it?
.
I think it is, yeah.Is the board potted ? (Sealed in epoxy or ?) I wonder if it could be back fed or tapped in to.
IDK, since it is mounted outside on the engine block, I would assume so...Is the board potted ? (Sealed in epoxy or ?) I wonder if it could be back fed or tapped in to.
Thanks Ronmar !You could. You could also pre-emptively replace it. I have been dealing with ECU’s for decades now and have never encountered an ECU failure. It supposedly does happen, but I have never personally experienced or heard from anyone who has had an ECU issue, working on a lot of Toyota, Honda and Mitsu... Normally removing power only wipes out stored codes and learned data, not the base program, This is what appears to happen to the cat, as the ECU failures I have read about and helped troubleshoot usually occured after a loss of vehicle battery power.
From what I have read(probably mostely here on SS), cat quietly admitted it made a design error and supposedly changed the design to be more foolproof(main program in non-volatile memory?) like other manufacturers apparently do...
unpredictability is part of the problem. Cumulative time without vehicle power may be a factor, age of the internal battery may be a factor, who knows but the person who designed it... I once worked on a radar system that used a keep alive battery on the main processor board. To change the battery you wrote the programming parameters specific to your installation(a lot of info) to a non volatile location, then replaced the battery, then you loaded the parameters back into working memory. But the basic program Operating System was in non volatile memory so the processor would reboot after the battery change. Why they didn’t make this an automatic process and skip the battery altogether is not clear...Thanks Ronmar !
Loss of (Main Batt) power for a couple of weeks didn't appear to have harmed my truck when it went through the battery theft and trying to figure out how to properly connect it back. It still doesn't appear to be the way it was - but now it has been so long ago - who knows.
Seems that if the MainBatt was a problem there would be all kinds of problems on the "sale yards" too.
Does the ECU have a port that receives programming? And if so, is that information CAT confidential? Maybe reading and pushing it onto an old ECU with a repaired battery? Just fishing. I would like to help if there are parts to play with...
THANKS for the info.