P2551
Torque Management Request Input Signal B High
Torque management / module communication
Generic OBD-II
Medium
What it means
P2551 means the "B" torque-management request signal — a line another module uses to ask the engine to reduce torque — is reading higher than expected. Systems like the transmission, traction, or stability control send these requests, so a high signal usually points to a wiring short or a fault in the requesting module. The engine may drop into reduced power until the bad request is resolved.
Medium
Can I keep driving? May run in reduced-power or limp mode — drivable but sluggish; have it diagnosed soon.
Common symptoms
What you'll notice
- Check-engine light on
- Reduced engine power or limp mode
- Hesitation
- Harsh or altered shifting
Common causes
Most likely first
- Wiring shorted to voltage on the torque-request circuitLikely
- Faulty requesting module (transmission, traction, or stability control)Common
- Poor connector or ground between the modulesCommon
- ECM faultLess often
How to diagnose & fix
Work through it in order
- Scan every module for related codes to see which one is requesting torque reduction.
- Inspect the torque-request circuit wiring and connectors between modules.
- Check the grounds shared by those modules.
- Confirm the requesting module is not sending a false high signal.
- Repair the shorted wiring or connector.
FAQ
Quick answers
Is it safe to drive with P2551?+
It will usually still move but may be stuck in reduced power. Drive gently and get it diagnosed rather than ignoring it.
Can I just clear P2551?+
It returns while the signal still reads high. Find the module or wiring sending the bad request first.
Related codes
Often seen with P2551
Read & clear P2551 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX