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Daniel Wilson
Daniel Wilson,
Category: Medium and Heavy Trucks
Satisfied Customers: 4663
Experience:  Owner at DJ Wilson
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I've got a 97 freightliner with a m11. I sold the truck

Customer Question

I've got a 97 freightliner with a m11. I sold the truck and it had a bad ecm from internal moisture. I removed the ecm of my truck that I was driving and replaced it with the one I sold. Now my engine temp light is coming on at 150 to 160 . I have changed
temp sensor both of the and the thermostat. The truck are identical vin numbers and engine serial number are staggered one being 34618945 and the other 34618946. Esn. What am I looking for I have no bent pins on my ecm.
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Customer: replied 1 year ago.
Let me clear I removed the ecm off the truc I was driving and put it on the truck I sold now my temp light is coming on on the truck I sold where it wasn't coming on before on the other truck. I replaced the thermostat and both temp sensors the one in the therm housing base and the neck. But I'm still getting a light and buzzer. Infared temp light indicated the temp is around after driving on all hose and housings .
Customer: replied 1 year ago.
Temp 160 - 170 after driving
Expert:  Daniel Wilson replied 1 year ago.

Hi my name is***** will be glad to try to help. First let me be sure I understand correctly.... Your current truck you swapped ECMs with the truck you sold which had moisture issues? So you kept the faulty ECM and put your good ECM on the truck to sell it?

Expert:  Daniel Wilson replied 1 year ago.

I recommend having your ECM reflashed if the problem never existed before the swap and all your connector pins look good as well as the harness. It sounds like it has to be a software issue if nothing else was done besides the ECM swap. Let me know

Customer: replied 1 year ago.
True in sold the truck which had a new recon ecm on it. But after it sat since 2007 the truck wouldn't start. We found the ecm had moisture. I swapped the ecm out to make good on the sell. Now I have the pro lem of the buzzer going off at 160 degree. Truck runs fine no engine shUT down. Just the temp buzzer. I trucks are identical. I mean literally they are both old maverick unit came off the assembly li e from freightliner one behind the otherapist even the engine serial numbers are one behind the other. My question is why would the ecm need reflashing if the tricks are spec exactly the same. I am looking logical reason to this.
Expert:  Daniel Wilson replied 1 year ago.

Thanks for the info. If the ECM had problems from moisture it is likely that there is corrosion internally that is now showing up with this problem you are having now. It is possible it is shorting this part of the circuit. Reflashing the ECM will help confirm if it can be resolved with the software and if not you will be replacing this ECM. You can have the ECM bench tested and reflashed.

Expert:  Daniel Wilson replied 1 year ago.

It is also possible that the ECM might be condemned on the bench test and attempted reflash.

Customer: replied 1 year ago.
When I put the ecm back on my truck I don't have the problem. So you think it could be corrosion in the harness?
Expert:  Daniel Wilson replied 1 year ago.

When you put the ECM back on a different truck? Or you remove the ECM and after reinstallation the problem is gone temporarily?

Customer: replied 1 year ago.
sir 2hen I put the ecm back on the truck it came off it doesn't come on. This trick I run qbck and forth to ky from arkansas weekly until I needed to make good on this sell. I will take it off again tomorrow and drive the truck about 20 miles to see if I get the same results.
Expert:  Daniel Wilson replied 1 year ago.

Thanks for the info. I would take a close look at the harness for corrosion and bare wiring. If ok and since you still have access to the sold truck check and see if the temp inputs and outputs are on the same pins for both trucks just to be sure. There should be 5v signal out and then the ECM reads the return voltage. Make sure you have good 5v signal as well.

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