P2551

Code

Generic P — Powertrain

Torque Management Request Input Signal B High

Brand: Generic

Type: P — Powertrain

Views: UK: 18 EN: 32 RU: 25

AI status

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Page language: EN

Causes

Open or shorted wiring on Torque Management Request B circuit (short to battery/voltage)
Corroded/damaged connector or bent terminals at the sensor or PCM
Faulty torque management request sensor/switch/module
Poor or missing ground for the sensor or PCM reference
PCM/ECM input stage fault or software anomaly
Water intrusion or contamination at connector or sensor

Symptoms

Malfunction Indicator Lamp (MIL) or check engine light on
Reduced engine power or limp-home mode depending on control strategy
Poor or delayed throttle response
Loss of cruise control or torque-limiting features
Inconsistent engine behavior when accelerator or brake inputs are used

What to check

Use a scan tool: confirm P2551, read freeze frame and related codes, note operating conditions
Perform a visual inspection of harnesses and connectors for damage, corrosion, or water intrusion
Back-probe the torque management request B signal with a multimeter and measure voltage (Key ON, Engine OFF and during cranking/running per service manual)
Disconnect the sensor/switch connector: check if the signal voltage remains high on the harness (indicates short to battery) or drops (indicates sensor fault)
Check reference power and ground circuits for continuity and proper voltage
Wiggle test wiring while monitoring signal for intermittent changes

Signal parameters

Expected: analog/digital request signal normally within a 0–5 V range (vehicle-specific). Typical operating window ~0.5–4.5 V.
Fault condition: signal voltage seen by PCM significantly higher than normal (often >4.5 V or near battery voltage).
Key ON, Engine OFF: reference voltage present on sensor supply (verify expected manufacturer value).
Low resistance expected between sensor ground and chassis ground; no short to battery on signal circuit.

Diagnostic algorithm

Verify the code with a scan tool. Record freeze-frame data and any other stored codes. Clear codes and attempt to re-create fault.
Visually inspect connectors and wiring for the torque management request B circuit; repair any damaged insulation, pins, or clamps.
Back-probe the request B signal at the sensor connector. With Key ON Engine OFF measure voltage; compare to expected range in step 4.
Unplug the sensor/switch. If signal voltage on the harness remains high, suspect a short to battery or PCM fault. If voltage goes to expected default, suspect the sensor.
Check continuity to ground and to battery power on relevant pins. Look for short-to-voltage (between signal and B+) or open/poor ground between signal and PCM reference.
If wiring and connectors test OK, swap or bench-test the torque management request sensor/switch (or replace with known good unit) and re-test.
If fault persists with a known-good sensor and correct wiring, test or replace PCM input or update PCM software per manufacturer guidance.
After repairs, clear codes and perform road/functional test to confirm the issue is resolved and codes do not return.

Likely causes

Damaged harness shorted to battery voltage on the request B signal
Corroded connector pin causing intermittent high voltage
Failed torque management request sensor producing out-of-range output
Missing ground or bad reference causing the PCM to see a high voltage
PCM internal input circuit failure (less common)

Fault status

⚠️ Status

Torque Management Request Input Signal B Circuit High — PCM detected the torque request B input voltage above allowable range, indicating a possible short to battery, sensor failure, wiring fault, or PCM input issue.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours