jnissen started following 2020 Sierra 1500 AT4 Duramax Cross-Country Towing Experience/Performance review, Chip.....ugh, Duramax 3.0 and and 4 others
Yeah sounds like assembly issues have not necessarily gone away. I wonder if better positioned strain relief on the harnesses and grounds are needed or just improper assembly to begin with? Did the engineer find this? Good to hear your up and running again. Better tow with it ASAP to determine if the engine movement will make it return.
Try an automotive incandescent bulb between the power and ground of the 7 pin. I suspect it’s looking at ground currents. Unless you have a fuse blown for the trailer power (possible) then you should at least see continuity through the bulb and see it light and remain lit. Make sure you use the 7 pin ground and not the bumper or other spot. If this works I suspect the computer needs to see some minimal current on the ground. You can try to find that minimum with various resistance loads. Sort of a PIA to debug it that way.
Call IPA at 888-786-7899. I don’t see anywhere in their literature about using the tool to test a 4 pin connector with an adapter. If your 4 pin trailer has been tested on other vehicles (recently) and it works then I’d look if that trailer may have LED lamps. The Denali may not detect enough current. Just a guess. Thought I read somewhere that a software update was in the works or already out to lower the brake current detection.
Why not use the standard 4 pin connector already on the truck? Not sure how this works using an adapter from the 7 to 4. Repeat with the 4 pin connector and let us know. Update: Believe you said you did test it. Just not clear if you were talking the adapter out or the default 4 out? BTW I’ve had no issues using either a 7 wire trailer or a simple 4 wire trailer. Both did the correct lighting. I’d verify what type of load that tester is applying for the 4 wire.
Around 3K miles on mine. No issues and tows awesome. Just keep an eye on the DEF if you tow as it can be thirsty under heavy load.
Where are you located? I’ve pulled my large dual axle enclosed trailer often and never had issues. I’m in Texas where it’s been 100+ heat. If your further west in the desert perhaps an under hood heat issue? We know the 3L generates a lot of heat under load. I’d push hard on your dealer to check the fuse block connectors. An intermittent fail at elevated temp and load sounds plausible.
LOL. He just has a different perspective. IMHO - If GM had more GrumpyBears we likely would have a better truck. I’ve been happy with my 2020 3L Duramax. That certainly will trigger a response.
Great report and lots of good advice.
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