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Have a 2016 Canyon with 77k. Ever since about 20k I have been getting this code on and off. Hasn't really affected drivability, other than when the Check Engine Light is on the engine brake doesn't work when towing.

The code is "ECM/PCM Power Relay Control Circuit Low" . I've read several posts about how the charging system on these trucks keep the battery at a lower voltage than most other vehicles. In the mornings when I crank it, the voltage on the dash readout is usually 12.0-12.2. I'm wondering if the actual voltage drops when cranking to below the threshold to trigger the code.

I haven't load tested the battery yet. Bought the truck in Nov. 2016, so the battery is 3 years old. But it has been throwing this code since 2017. My fault for not taking it in while it was still under warranty.

I've swapped around relays in the fuse box, but I'm not sure if the actual ECM/PCM relay is there or somewhere else. Internet searches have failed to tell me the exact relay, and I haven't seen any posts with others having the same issue.
 

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There is a known wire chafing issue on the trucks. Could be your issue. I posted about it somewhere on here. Use the search feature and look for “wire chafing” and you should find it. Might be your issue, might not.
 

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I recently started getting this code also. Haven't checked to see if wire chafing could be the issue yet, but about the same time this started, the remote start went inop. I started monitoring the voltage before starting and have seen it as low as 11.5, but typically 11.7-11.8 in the mornings and higher when it doesn't sit overnight. No issues starting it though - doesn't seem sluggish or anything.

Could the low battery voltage cause both the P0686 and remote start issue or is chafing still the primary suspect?
 
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