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spankyjr1, Journeyman
Category: Medium and Heavy Trucks
Satisfied Customers: 2612
Experience:  I worked on all types of equipment semis,forklifts,farm,ect.
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I have a 07 freightliner columbia that has a electrical gremlin,

Customer Question

I have a 07 freightliner columbia that has a electrical gremlin, when driving the check engine would come on, oil pressure & coolant temp. gauge go to zero and loose power. I stop then notice when I turn off my headlights the check engine light goes away turn headlight on engine goes back on. It happens when it gets wet but once when completely dry. no fault codes either. Another kicker also when I turn off headlighgs the engine fan kicks on.
Submitted: 2 years ago.
Category: Medium and Heavy Trucks
Expert:  spankyjr1 replied 2 years ago.
Hi, my name is ***** ***** you for your question.
Sorry for delay.
These gage readings you are loosing come from engine ecm (oil pressure & coolant temp)over what is called a data link connection which is a twisted pair of wires from engine ecm to cab ecm.
They go from engine side of firewall into cab through pass through connections.
Remove and clean all pass through connections on firewall engine side.
If there are any open connections clean out with electrical cleaner and cap off so no moisture can get in.
If they get wet they can effect data coming across data link.
This can cause all your issues.
I would also remove and clean all battery cables and engine grounds even by starter and up on firewall.
Since this problem shows up with headlights on it may be low voltage causing issue.
The engine kicks fan on since it can't see engine temp for engine safety.
I would also remove battery negative cables and ecm connectors clean and re install.A poor connection can cause this issue.
If you have questions or problems let me know I'm happy to assist.
Thanks in advance for leaving a positive rating. If you happen to need more help, this question will stay open for weeks.
Customer: replied 2 years ago.
Hello Spanky,
I do appreciate the response, I started driving and it seems either a loose connection on the data link cable or moisture get out, that the issue comes and goes as I drive. I had my mechanic check and said the same thing he said he didnt find anything wrong evidently there is. I dont know if freightliner sells new ecm data link cables or have to manually remove and clean the whole thing. Also how do all these correlate and no codes show?
Expert:  spankyjr1 replied 2 years ago.
You most likely don't need a new cable unless it got worn through somewhere,, so check wiring from cab to engine ecm closely.
Pay close attention around hot or moving parts,,,loom clamps,,,wire ties that are to tight can wear through wire internally from vibration.It sounds like you have either corrosion or loose pin sockets so try moving wiring around while someone watches light for you while engine is running,,this might pin point your issue.
You must have codes stored in engine ecm because anytime check engine light comes on it stores codes.
The codes won't be active but logged into ecm memory.
They must be read by a Detroit scan tool,, not all other scan tools will read the codes.
Any dealer that works on Detroit engines has the correct tool to pull codes.
You can purchase new data link from dealer but I would hold off until you check what I said first.Most times its just a connector issue or corrosion.
Corrosion when wet acts like a conductor connecting pins together in a plug but once it dries out it looses that connection.