augsterformula Posted February 12, 2022 Share Posted February 12, 2022 We have a 2002 Mack CL with the ETEC 460 that is giving us an occasional blink code 6-4. When the electrical malfunction light comes on, the truck stays running but has no throttle and rpms go to 900. We discovered by accident that if you tap on the kick panel on the passenger side, the code will always clear and the truck will run fine again, but you can never get the code to set by tapping the kick panel. We checked the wiring plugs on the ECU and VCU and everything looks good. It seems to be extremely random and some days the truck is completely fine and some days the code comes and goes. Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted February 12, 2022 Share Posted February 12, 2022 Hey bud, 6-4 is a communication code for the 1939 line... it's the yellow and green 'twisted pair'.. check the pin condition and tension at the VECU, and at the Diagnostic port, under the dash above the clutch pedal.. check voltage at these 2 pins,, low side is about 2.5 volts and high line is about 5+ volts... I dont remember the exact volts but im pretty close.. there is also a triangular duetch plug on the firewall along with the many harness's near where the steering shaft comes out of the wall.. I know you said you can kick the panel and it changes the truck.. so maybe you missed something during inspection.. jojo Quote Link to comment Share on other sites More sharing options...
augsterformula Posted March 19, 2022 Author Share Posted March 19, 2022 Thanks @Joey Mack. Checked the plugs you mentioned, took them apart and looked at them. Everything looked good, pins were all clean. Put it back together and it hasn't acted up since. Hard to troubleshoot when it happens so random and never acts up long. Weirdest thing the last time it did it was you couldn't shut the truck off, if you turned the key off if would shut down but just before it stopped completely, it would fire back up and stay running. Did that a couple times that we cycled the key, then the code cleared and everything worked fine again. Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted March 19, 2022 Share Posted March 19, 2022 so to be clear is it fixed now? if so, my guess would be that you improved a connection when you plugged things back in... jojo Quote Link to comment Share on other sites More sharing options...
augsterformula Posted March 19, 2022 Author Share Posted March 19, 2022 It was very random before, some days it would act up and the next day you could run it all day and it would never do it. It always would go away as soon as you started to try to diagnose it. Hasn't done it since we checked all the wiring, although we haven't used it much since, so we will see. Hoping that fixed it. We don't use the truck every day and sometimes it goes a couple of weeks without being used. Thanks for the help 1 Quote Link to comment Share on other sites More sharing options...
augsterformula Posted April 30, 2022 Author Share Posted April 30, 2022 Well the truck sat unused for a couple of weeks. Used the truck again the other day and the issue is back. Put probably 3-4 hours on the truck and it did it once while pulling a pretty good hill. Smacked the kick panel on the passengers side and it cleared up and ran fine the rest of the day. This thing is making me pull my hair out. Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted April 30, 2022 Share Posted April 30, 2022 Man I wish I had been in one recently.. to refresh my memory. I know there is a group of ground wires left of the fuse panel behind the panel that says CL 700.. Have you checked it? Quote Link to comment Share on other sites More sharing options...
Hans Remmers Posted May 1, 2022 Share Posted May 1, 2022 I dealt with a similar issue with the transmission controller on a Cat D5 dozer. It would lock up and the machine wouldn't move, smack the TCM with a wrench and all is fine. Never had to deal with it any further but would've replaced the trans module if had to. I wouldn't rule out the possibility that the VCU behind that kick panel is going bad. 1 Quote Link to comment Share on other sites More sharing options...
augsterformula Posted May 1, 2022 Author Share Posted May 1, 2022 @Joey MackI will check, I think you are right and there is a group of ground wires in there. @Hans RemmersI am beginning to question the VCU also, may have to look for another VCU. Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted May 1, 2022 Share Posted May 1, 2022 Hans, there is only one in the kick panel... the other is ABS.. your right.. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.