P2551 code meaning
Torque Management Request Input Signal B High
Powertrain system Generic code P25xx codes Check engine light
What P2551 means
P2551 is the high-side fault of torque request B: the signal sits above the top of its valid window. Typical electrical causes would be a line touching a battery feed, an interrupted reference ground or a sender that drives its output to full scale. Because an unexpectedly high request could translate into unwanted torque, the engine module discards it and works without channel B. No maker documents P2551 publicly. GM's ECM table 17OBDG04 shows that a vehicle can fill channel B with the brake and traction module's request and validates it with protection value and message counter under P2548, with no separate high code. CARB requires monitoring of such electronic inputs whenever a failure could raise emissions or blind another monitor. P2550 is the low-side fault, P2547 the high fault on input A.
P2551 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P2551
- Check engine light depending on make
- Traction control warning, engine ignores intervention requests
Common causes of P2551
- PossibleRequest line shorted to battery voltage
- PossibleOpen ground or reference at the sender
- Less likelyRequesting module drives its output to full scale
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Torque management input b
What each part of P2551 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| 51 | The exact fault in that area. |
What to do next
- Note P2551 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P2551
What does P2551 mean?
P2551 means "Torque Management Request Input Signal B High". P2551 is the high-side fault of torque request B: the signal sits above the top of its valid window. It is a generic code, so it means the same on every make.
Is it safe to drive with P2551?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P2551 fail an emissions test?
Yes, it can. P2551 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P2551 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P2551 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.