2016 Pete 389 interior/cecu problems
12-01-2020, (Subject: 2016 Pete 389 interior/cecu problems ) 
Post: #1
2016 Pete 389 interior/cecu problems
2016 Pete 389 w/ cummins

I noticed that my cab is not grounded by using my power probe. So I started checking grounds and I noticed that the cab, frame and starter grounds all show 0.25 volts. The batteries all show good ground, but when I turn the key off and close the doors, once the interior lights turn off they all show good ground. Also, a select half dozen or so gauges and switches have backlights on at all times. Unless batteries are disconnected of course. The backlights have been like this for almost two years now since we owned the truck. The grounding/voltage scenario just started this week.

Any help is appreciated. TIA
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12-03-2020, (Subject: 2016 Pete 389 interior/cecu problems ) 
Post: #2
RE: 2016 Pete 389 interior/cecu problems
Pete and kw (paccar) cecu's are notoriously flaky. Disconnecting ALL batteries and power sources to the truck for 30 minutes + so that the residual power and memory on the circuit boards in them finally dies will hard reset them and cure many ailments they get themselves caught up into.. Dash gauge lights not operating as intended, speedo sometimes acting up, and a lot more ghost problems. It is a well known issue that has been around for years now and also has been discussed on here many times in the past. You would think that by now every damnned stealers%$it and repair shop in the usa should know this .. yet they all seem to have some kind of amnesia when it comes to this issue.


Unlike older trucks and cars of yester-year ... The cab and chassis grounds are not used by the electrical system at all on all modern trucks ... The fact that it has some electrical noise in it is mostly meaningless outside of ensururing they are grounded properly. Just ensure some moron did not connect a gauge, device, or other thing that did not come with the truck from the factory to the chassis to get a ground... ALL grounds should come from the wiring harness alone and none of them should reference or draw current off any of the metal surfaces of the cab, chassis, etc.

The chassis and cab and other things do have a ground wire going to them to prevent static voltage buildup, etc. but that is their only purpose. Nothing should be connected so that it draws (negative voltage feed) and be power by it though.


If some moron hooked up a CB-radio or e-log device and tied the negative wire to the chassis somewhere instead of the grounds in the wiring harness, this could be some issue... or in the extreme case, for all anyone knows, the used truck stealers$it or someone else could have installed a GPS tracking device hidden way up into the dash of the truck to track it and sell the information online or to track it in case you decide not to make truck payments... and they could have tied the ground wire to the chassis like a fool.... i cannot tell you how many dozens of hidden tracking devices I have found inside people's trucks that have come over here to visit... who had no clue that someone had installed one into the truck before they purchased it... many of which are wired up half-arsed like this.

Lastly, as far as measuring slight voltage differences on the chassis ... most digital modern volt meters are notoriously bad at picking up static garbage (like a radio antenna would) when connected to large metal surfaces vs. an old analog type of meter...use an old style analog style of volt meter when you think you are chasing electrical noise to eliminate the static differences the large metal surfaces might be imposing on a digital meter.


User's Signature: ->: What I post is just my own thoughts and Opinions! --- I AM Full Of S__T!.
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 Thanks given by: indian_richard , Waterloo , Coronado126
12-05-2020, (Subject: 2016 Pete 389 interior/cecu problems ) 
Post: #3
RE: 2016 Pete 389 interior/cecu problems
Thank you rawze for the feed back! Much appreciated. I’m using a power probe to reference the voltage, or lack of. I’m gonna disconnect the batteries for a few hours tomorrow and see how that works. If that doesn’t change anything, what would you do next? I don’t have the software for these yet, but I’m working on it.
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12-05-2020, (Subject: 2016 Pete 389 interior/cecu problems ) 
Post: #4
RE: 2016 Pete 389 interior/cecu problems
Like Rawze was saying, the CECU is not a very robust module. I've had to change a couple handfuls over the years due to various failures. Gauge backlighting being one or two of them.

You're next bet if the battery trick doesn't work, would be tracking and checking every power and ground for that CECU. Let me look around on my laptop I believe I have the proper wiring diagram for it to give you.

If those are good, then your probably looking at replacing the CECU.

One question though, the gauges/switches that stay lit up, is it always one part of gauge cluster? Or does it vary?
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 Thanks given by: indian_richard
12-05-2020, (Subject: 2016 Pete 389 interior/cecu problems ) 
Post: #5
RE: 2016 Pete 389 interior/cecu problems
Have a 2015 Kenworth T660.
Sometimes the mileage, trip and I think hour meter will just show dashes. Turn truck off for a while and will work again. Has happened about 3 times in a year.

Have had interior lights not come on when you open the door. Again turn truck off for awhile and then they will start to work.

Gauge lights not coming on 3 or 4 times in a year. When you turn the headlights on the mileage would dim but the gauge lights doesn't come on. Turn off truck for awhile and then they go back to working.

Also have seen my HVAC not change from defrost to floor heat. If I turn knob to floor and dash vents then it will correct its self. Can turn back to floor and that's where it will blow. Turn to floor and defrost and it goes to all defrost.

Like mentioned Paccar is full of ghosts in the cab.


User's Signature: 2015 Kenworth T660
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 Thanks given by: indian_richard
12-06-2020, (Subject: 2016 Pete 389 interior/cecu problems ) 
Post: #6
RE: 2016 Pete 389 interior/cecu problems
(12-05-2020 )Coronado126 Wrote:  Like Rawze was saying, the CECU is not a very robust module. I've had to change a couple handfuls over the years due to various failures. Gauge backlighting being one or two of them.

You're next bet if the battery trick doesn't work, would be tracking and checking every power and ground for that CECU. Let me look around on my laptop I believe I have the proper wiring diagram for it to give you.

If those are good, then your probably looking at replacing the CECU.

One question though, the gauges/switches that stay lit up, is it always one part of gauge cluster? Or does it vary?

Thank you for sharing your experience with the CECU’s because I have, literally none.
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12-06-2020, (Subject: 2016 Pete 389 interior/cecu problems ) 
Post: #7
RE: 2016 Pete 389 interior/cecu problems
(12-05-2020 )Mattman Wrote:  Have a 2015 Kenworth T660.
Sometimes the mileage, trip and I think hour meter will just show dashes. Turn truck off for a while and will work again. Has happened about 3 times in a year.

Have had interior lights not come on when you open the door. Again turn truck off for awhile and then they will start to work.

Gauge lights not coming on 3 or 4 times in a year. When you turn the headlights on the mileage would dim but the gauge lights doesn't come on. Turn off truck for awhile and then they go back to working.

Also have seen my HVAC not change from defrost to floor heat. If I turn knob to floor and dash vents then it will correct its self. Can turn back to floor and that's where it will blow. Turn to floor and defrost and it goes to all defrost.

Like mentioned Paccar is full of ghosts in the cab.

I have also had this happen too! With the trip/odo showing all dashes! I forgot to mention that too. For whatever it matters I’d like to know if that’s an indicator as well. I disconnected the batteries today at the end of the day so I’ll reconnect them tomorrow and see if that changes anything.
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12-06-2020, (Subject: 2016 Pete 389 interior/cecu problems ) 
Post: #8
RE: 2016 Pete 389 interior/cecu problems
I just wanted to say thank you for all your input on this issue I’m having. The knowledge you guys pass on from your experiences are greatly appreciated.
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02-25-2021, (Subject: 2016 Pete 389 interior/cecu problems ) 
Post: #9
RE: 2016 Pete 389 interior/cecu problems
The unhooking of the batteries for an hour didnt change anything for me... Im still having lighting issues ... and this years focus durring the revenue round up is LIGHTING... Im gonna be screwed.
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