- 679
- 983
- 93
- Location
- Texas Hill Country
Unless you install an old controller in a newer truck; then you may run a foul the J1939 circuit instead—Default pressure is different for different trucks. 55 psi on most. M1088 and M1089 run 81 psi for highway. There is no standard default - it depends on the chassis harness configuration so that if you swap modules between trucks it will load the correct pressure for that chassis. That's what the option pins are for - to tell the controller what chassis it's installed in.
