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+--- Thread: 2020 Peterbilt 389 / Cummins X15 – Brake pedal always shows depressed after ECM swap, (/showthread.php?tid=10615)
2020 Peterbilt 389 / Cummins X15 – Brake pedal always shows depressed after ECM swap, - Ripon_guy - 05-29-2026
Hi everyone,
I’m hoping to tap into the collective knowledge here. I bought a 2020 Peterbilt 389 with a Cummins X15 at an auction. The truck came without an ECM.
2020 Peterbilt 389 Vin 1XP-XA48X-4-LD732535
Ecm I’m using
ESN 80140981
P/N 4384413
S/N 22357078
D/C 01252019
E/C HD10357,00-60000
00000
CM2350
5532
I got a used Cummins ECM from a 2020 International with the same CPL. I had it rewritten using a calibration from a similar year Peterbilt with similar specs. After installation, everything works except the brake pedal signal.
The problem:
· In Cummins Insite, the brake pedal status is always “depressed.”
· In ESA (Electronic Service Analyzer), the brake pedal status changes correctly between “depressed” and “released” when commanded.
· The brake lights work normally.
· The truck won’t regenerate and is in derate.
What I’ve tried so far:
1. Checked the brake valve and brake pedal switch – both are functioning properly.
2. Sent the ECM to Peterbilt to have it bench-updated and rewritten to match my Peterbilt’s VIN and specs. No change.
3. Swapped in another ECM from a known working Peterbilt with the same X15 specs. The problem remains exactly the same.
At this point, I’m confident the issue is not the ECM itself, but maybe a mismatch in parameters, wiring, or how the brake signal is being interpreted by the engine ECU.
Has anyone else run into a similar situation after an ECM replacement across different chassis (International to Peterbilt)? Could this be a configuration issue in Insite (e.g., brake switch input type, CAN vs hardwired, or something in the vehicle parameters)? Any advice on what to check next would be greatly appreciated.
Thanks in advance for any guidance.
RE: 2020 Peterbilt 389 / Cummins X15 – Brake pedal always shows depressed after ECM swap, - Rawze - 05-30-2026
(05-29-2026 )Ripon_guy Wrote: ...
2. Sent the ECM to Peterbilt to have it bench-updated and rewritten to match my Peterbilt’s VIN and specs. No change.
...
my first thoughts...
it could still be in the ecm. - Many stealers$hits will use the default options in Insite (re-use the existing data in the ecm) when re-flashing the software instead of manually cancelling it and pulling from their database like they should.
I.E.> You should have completely blanked out the ecm or flashed it with the blank versions of the correct program according to enigne ser#, and NOT saved/restored any data/template/work orders ... then send it to them to recover the vehicle data into it on that vin#.
that, or purchased an official replacement ecm from the stealers$it and had them pre-flash it with engine software and vehicle-specific settings, etc. before accepting it.
and yeah, those switches and addresses for buttons, etc. change year to year and model to model on those petes.
Personally, I would not have purchased the truck unless you had the extra moneys to inframe it. Who knows what kind of bad things may have happened to it if it had a bad delete or something in that ecm they took off it.
RE: 2020 Peterbilt 389 / Cummins X15 – Brake pedal always shows depressed after ECM swap, - Ripon_guy - 05-30-2026
Thanks for replying. I think so seems like peterbilt didn’t even touch it.