P2550 Torque Management Request Input Signal B Low

P2550 marks the second torque request input, B, as stuck below its lower limit. A hard-wired line would be pulled to ground by chafed insulation or a fault in the sending stage; in a networked design the sender would be reporting a value that lies under the bottom of the defined range. The engine module then disregards input B and keeps running on its own torque calculation. No maker documents P2550 publicly. GM's 2019 table 19OBDG03A assigns the B channel to the traction request of the electronic brake and traction control module, sent in messages $1C8/$237, and checks it only with the general code P2548. CARB requires electronic inputs to be monitored for out-of-range values when they influence emissions. P2551 is the high-side fault, P2546 the low fault on input A.

Likely causes

Symptoms

• Check engine light depending on make
• Traction-related torque reduction no longer applied

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

Related codes

References: law.cornell.edu, gsi.ext.gm.com.