No Throttle Response, Then Blown Fuse 64 For Ecm

Mark Mobile Technician Ontario Posted   Latest   Edited  
Unsolved
Driveability
2014 Ram 1500 Big Horn 5.7L (T EZH) 8-spd (845RE)
P2100 — Throttle Actuator "A" Control Motor Circuit/Open
P0685 — ECM/PCM Power Relay Control Circuit/Open
P0688 — ECM/PCM Power Relay Sense Circuit/Open
No Throttle Response
Blown Fuse 64

I was helping a shop a couple of weeks ago for a intermittent p2100 ( throttle actuator control motor /circuit open ) ..When the code set, the truck was in limited power mode. The shop replaced the throttle body but the code came back with same problem. I then suggested that the only things remaining for the code is wiring or the computer. I wired in 2 wires for the + and - that the pcm controls the throttle body motor. The vehicle did not act up , the customer took truck and did not act up for a about 10 days.. ..Before this code could be duplicated quite often probably within a day. Today being 10 days after ,the truck was towed in for a no start. Customer bitching and complaining..What else is new.. The tech hooked up scanner and found 2 codes p0685, ecm power relay control circuit open, and p0688 ecm power relay sense circuit open. The tech found fuse 64 blown. ( fuel injector ecm fuse) .

The owner of the shop is trying to say that wiring in the new wires for the throttle body motor could cause the fuse to blow and im saying ,NO DAM WAY, its something else. So to me ,there maybe more gremlins in the wiring .

Where do i start?I guess i start seeing what fuse 64 feeds, all branches and its source of power ..Has anyone see something like this on a truck and close to year and model?

Much appreciated. 

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Glenn Owner/Technician
Texas
Glenn
 

Hi Mark, Ah! The joys of being mobile…. Get the wiring diagrams and flow charts related to all the codes, study them and trace down the harness. I suspect it may lead you back to an SBJ problem, but prove it is the issue (don't go off of a hunch). Any TSB's? The earlier P2100 code was just the "tip of the iceberg". Look for any signs of aftermarket equipment, prior repairs or bodywork. A…

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Mark Mobile Technician
Ontario
Mark
   

thanks glenn. After a bit of a heated discussion with the owner of the shop , hes beginning to believe me when i say the rewiring for the throttle body motor has nothing to do with this fuse 64. It doesnt not make sense to me .If the pcm saw a short , it would not use the circuit and the system would go into limp throttle mode. So he needs to tell the customer we must rewire that circuit for…

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Aaron Technician
Illinois
Aaron
 

Inspect pcm connector for water intrusion

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Timothy Owner/Technician
Wisconsin
Timothy
 

The fuse COULD be involved in this scenario. The PCM feeds the ETC power and ground, so the fuse may be involved (through the PCM circuits internal to it), despite there being no apparent connection outside the PCM. I've seen throttle body circuit codes because one of the feeds to the PCM had an issue. That said, it could be wholly unrelated, and just be a case of “Eversincha”.

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Mark Mobile Technician
Ontario
Mark
 

THANKs.. My thinking is if amperage in that circuits for throttle body motor is to high ,the pcm should stop using it. The pcm will stop using those 2 circuits if there is an open or short because there r codes engineered for that. There should be protection in those circuits . Yes ,in older vehicles ,this could be a problem to blow a fuse but newer technology like this? Fuse 64 is asd output…

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Timothy Owner/Technician
Wisconsin
Timothy
 

That is what I was referring to: the fact that the fuse feeds the PCM. All circuits that need power from the PCM (Chrysler uses high-side drivers more than most OEMs, such as O2 heaters, etc.), get it from outside the PCM through powered (usually fused) circuits, it's not magically produced from nothing. It has to come from somewhere.

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Mark Mobile Technician
Ontario
Mark
 

Yes. The only thing i did was wire in new wires for the throtlle body motor + and - going from the pcm to the throttle motor because i suspected the wiring may be shorted inside the harness because it had an intermittent p2100 with limp mode and throttle body replaced. That problem went away. So if the original problem was not a new throttle body ,in which they replaced first, so r u saying the…

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