P2640

Torque Management Request Input Signal A Low

P2640 is a generic OBD-II powertrain diagnostic trouble code: Torque Management Request Input Signal A Low. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P2640
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P2640 means

P2640 is stored when the PCM/ECM detects that the torque management request signal on circuit A is below the expected minimum threshold. This signal is used by the powertrain control module to coordinate torque reduction requests from subsystems such as the transmission control module, traction control, or stability control system.

The fault typically indicates an open circuit, short to ground, or a failed signal source on the torque request input line. The PCM monitors the voltage or digital signal on this line continuously and sets the code when it falls outside calibrated limits for a defined period.

Drivability impact varies by vehicle: some systems operate in a reduced-performance mode while the fault is active, limiting torque output as a precaution. Clearing the code without repairing the underlying wiring or module fault will result in the code returning quickly under normal driving conditions.

Common causes

Most-frequently reported root causes when P2640 is logged.

  • 1
    Open or broken wire in the torque management request signal circuit A.
  • 2
    Short to ground on the torque request signal wire.
  • 3
    Faulty transmission control module (TCM) not outputting the torque request signal.
  • 4
    Corroded or damaged connector at the PCM or TCM harness junction.
  • 5
    Failed traction or stability control module that shares this signal network.
  • 6
    PCM internal input circuit fault causing incorrect signal reading.

Symptoms drivers notice

MIL (check engine light) illuminated.
Reduced engine torque or power limitation active.
Traction control or stability control warning light may also be on.
Harsh or abnormal automatic transmission shift behavior.
Possible loss of traction control functionality.

How to diagnose P2640

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool and record all stored DTCs; note any TCM or ABS/ESC codes present alongside P2640.
  2. 2
    Review freeze frame data to identify operating conditions when the fault was set.
  3. 3
    Inspect the wiring harness and connectors between the TCM and PCM for damage, corrosion, or chafing.
  4. 4
    Using a multimeter, check the signal circuit A wire for continuity and absence of short to ground with connectors unplugged.
  5. 5
    With the ignition on and connectors reconnected, use the scan tool to observe live torque request signal data from the TCM.
  6. 6
    If wiring is intact and the TCM appears to not be sending the signal, check TCM power and ground supplies before condemning the module.
  7. 7
    Replace or repair the faulty component and retest; clear codes and verify the fault does not return under normal driving.

Related powertrain codes

Frequently asked questions

Can I drive with P2640 active?

Short-term driving is generally possible, but torque may be limited and traction/stability control may be impaired, increasing risk in adverse conditions. Diagnose and repair promptly.

Is P2640 always a wiring problem?

Wiring faults are the most common cause, but a failing TCM or PCM can also produce this code. Always check wiring and connectors first before replacing modules.

Will P2640 cause the transmission to shift differently?

Yes. Because the TCM uses the torque signal to coordinate shifts, abnormal shift quality or firmness may be noticed when this code is active.

Does P2640 affect fuel economy?

Indirectly. If the system defaults to a conservative torque strategy, the engine may not respond optimally to throttle inputs, potentially affecting efficiency.

Disabling P2640 in software

RaceTune can permanently disable P2640 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

ECUs with a P2640 disable in our catalogue

Confirmed coverage from our recipe database — we support many more families. Upload your file and our identifier will match it automatically.

  • Bosch MD1CS001 verified 1 software version

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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