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anthony920
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Any ideas? Checked continuity and voltage on all wires at VECU. Also, checked continuity and voltage on all wires at ECU. Checked all fuses and relays - all good and voltage good. Ohm'ed J1939 wires all good. Installed good test VECU and ECU still no start. Have good fuel pressure. Computer will not talk to data link. Any suggestions will be appreciated.

Ok my gynisis computer wont talk with going to try prolink tomorrow. I have also tried a new cam sensor still no start. First day checked out wiggled wires and disconnected plugs on trans and after a bit it started. Drove to yard and died at yard. Next day cleaned all battery terminals and positive and negative on chassis. Truck started, killed it and then would not restart.

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Any ideas? Checked continuity and voltage on all wires at VECU. Also, checked continuity and voltage on all wires at ECU. Checked all fuses and relays - all good and voltage good. Ohm'ed J1939 wires all good. Installed good test VECU and ECU still no start. Have good fuel pressure. Computer will not talk to data link. Any suggestions will be appreciated.

Ok my gynisis computer wont talk with going to try prolink tomorrow. I have also tried a new cam sensor still no start. First day checked out wiggled wires and disconnected plugs on trans and after a bit it started. Drove to yard and died at yard. Next day cleaned all battery terminals and positive and negative on chassis. Truck started, killed it and then would not restart.

I think trying to use the Prolink on step 10 software and higher is supposed to corrupt module data. Is you diagnostic connector 6 pin or is it 9 pin? I've seen some problems with the 9 pin connectors not communicating due to damaged or unseated pins. If your EML is flashing a 6-4 the problem is likely in the wiring to the engine or in the power up sequence of the modules. You probably have no communication on the J1587 datalink as well as on the J1939. It kind of sounds like power relay #3 may be sticking which causes incorrect power up of the modules or no power up at the engine ECU.

"Mebbe I'm too ugly and stupid to give up!"

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It is a 9 Pin. I have checked the voltage across all 4 of the big relays with key on and they are ok. Does this have a timing sequence that may be off.

The modules have to power up in sequence, VECU first EECU second.

Check fuse 16 for power with the key on. This is the fuse that supplies switched power to the VECU. The VECU puts this power out on wire VJ3-13 as the control wire to the coil on the power relays. If you have power at the fuse with the key on check to see if you also have power at pin 85 on the power relays (you should). Next check that there is no power at pin 85 of the relays with the key off (you shouldn't have power there with the key off). If everything so far is ok, check pin 86 for continuity to ground (should have continuity to ground). If the coil wires (pins 85 and 86) are correct then check to see if you have power at fuse 40 (EECU power). This fuse outputs power to the EECU on wires EJ2-10, EJ2-22, and EJ2-41. If you get power here with the key on check for continuity to ground on wires EJ2-12, EJ2-24, and EJ2-43

If you don't want to do all of these checks you might try replacing the power relays and checking the female terminals in the fuse panel for a loose fit, I've seen that happen more than once.

"Mebbe I'm too ugly and stupid to give up!"

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I have checked all fuses and they have power with key on. Also VJ3-13 it has voltage,fuse 40 is good. I think I check for voltage on the EJ2 at pins at the middle three large pins i believe, and check for continuity on the bottom three. I have removed all harness protectors and checked all wires from bulkhead to EECU. Sorry I have tried to check all this, I am just at wits end don't know what else to check, thanks for your response. Could these relays just be sticking as you said, and be coming on but too late. I also switch all four of them around several times.

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I have checked all fuses and they have power with key on. Also VJ3-13 it has voltage,fuse 40 is good. I think I check for voltage on the EJ2 at pins at the middle three large pins i believe, and check for continuity on the bottom three. I have removed all harness protectors and checked all wires from bulkhead to EECU. Sorry I have tried to check all this, I am just at wits end don't know what else to check, thanks for your response. Could these relays just be sticking as you said, and be coming on but too late. I also switch all four of them around several times.

I wouldn't think all four power relays would go out at once. It's more likely that the pins in the fuse panel are loose, but that's not necessarily the problem either. Try checking the grounds at the engine block, frame rail, cab ground breaker, etc. Check the 15 pin connector that is over the top of the transmission too. If you have another truck you might try swapping the ECU's around.

"Mebbe I'm too ugly and stupid to give up!"

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I cleaned the grounds at the block frame the cab ground braker on post is good although I wenta ahead and put the two wires together. I swapped the ECU with one from salvage yard not sure if its good for sure though. I checked all fuses by removing and checking for voltage then raising fuse and checking voltage on both sides. I also removed the positive cables at the frame and cleaned, they were loose and corroded so I thought I had finally found the problem. I checked the pin connector over trans and ohm'ed wires on each side of plug all ok.

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Tried ProLink today and it won't talk to it. Also, Engine Shut Down Light does not come on.

If you can't communicate with it your J1587 is not functioning either. One or the other of the datalinks has to be operational to start the engine. Check for worn wires on both datlinks that may be shorting out. I am doing the same thing right now. The datlink wires for the J1939 were still intact but the insulation was rubbed through allowing an intermittant short that was causing a fault.

"Mebbe I'm too ugly and stupid to give up!"

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I replaced the VECU with a 1999 model and this is a 2006 - could that be the problem?

The VECU software will not match with the EECU software and will cause a 6-4 code unless the VECU is programmed with the software and datafile for the truck by a dealer.

"Mebbe I'm too ugly and stupid to give up!"

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  • 8 years later...
4 hours ago, C1065 said:

I’m having the same problem.After the starter motor was replaced,the engine just cranks and will not start.Fuses good.Power and ground to VECU and EECU good.Any help would be appreciated.Thanks.

Go back in the chassis, dig around and find the power leads or ground run you did not attach to the starter post. Not everyone is getting fed.

Edited by Mack Technician
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  • 10 months later...

I have the same problem but I can jump start my truck through the starter. The problem started with my vecu back two weeks ago I had a blown fuse for air suspension and def lock so I went took out the fuse I didn’t had matching 15a fuse so I put 20a then oh boy some nasty smoke came out of my vecu and ya i fried my vecu still don’t know what cause that but I went out got the vecu from same truck as mine and everything worked fine just have check engine light on all the time but no problem running the truck I know I had to go to dealer to clear all the codes and have them put my Chasee number all that and all the sudden I was driving my R light for reverse gear comes and go while I’m going 115km and then it stopped every thing was fine until I pulled over in the rest area and took nap woke up I had grade gripper malfunction light on and thunder bolt light on so i thought let’s turn the truck off which was bad idea and it will not start I mean no power to starter and my mdrive start flashing ** no gears and I played with some relays and got the truck started and moved right of way from there lights comes and goes and no gear displayed got to the flaying j so I thought turn it back off this time nothing worked truck is off unless I go jump starts from the starter which I did but m drive not responding any ideas already spent $40000 on this truck this year don’t have the money to spend more any help please let me know 

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  • 4 months later...

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