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Federal Military Parts (763) 310-9340

Throttle Position Sensor (TPS) for Military HUMVEE 6.5L HMMWV 12554488

€200,00 EUR
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For the mechanical-injection 6.5L diesel HMMWV (M998, M1025, M1038, M1097, M1123, etc.), the Throttle Position Sensor (TPS) mounted on the injector pump typically uses:

Description Part Number NSN
Throttle Position Sensor (TPS) 12554488 2990-01-426-4425
Alternate manufacturer number GEP18002829 2990-01-426-4425

The TPS is mounted on the side of the injection pump and sends a variable voltage signal (approximately 0.5V to 4.5V) to the transmission controller for shift timing and torque converter operation.

The Throttle Position Sensor (TPS) part #12554488 is an electronic rotary potentiometer used on military HMMWVs (Humvees) to convert throttle lever movement into a variable voltage signal. 

What Does It Do?

On a military Humvee equipped with a mechanically injected GM/GEP 6.5L diesel engine (DB2 mechanical injection pump), engine fueling is controlled mechanically via the throttle linkage. Because the engine does not rely on a computerized engine control module (ECM) for fuel injection, the TPS is primarily used to provide engine load data to the Transmission Control Module (TCM).
  • It reads the driver's throttle input and sends a 0.5V–4.5V+ signal to the TCM.
  • The TCM uses this voltage alongside vehicle speed to determine shift scheduling, line pressure for gear engagement firmness, and torque converter clutch lockup for the electronically controlled 4-speed 4L80-E transmission.

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    Which Vehicles Use It? (Is It on Every Humvee?)
    No, it is not used on every military Humvee.
  • Where it is used: It is installed on A2-series and later HMMWVs equipped with the 6.5L naturally aspirated or turbocharged diesel engine paired with the 4-speed electronic automatic transmission (4L80-E). Common variants include the M998A2, M1097A2, M1114, M1123, M1151, M1152, M1165, and civilian Hummer H1s.

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  • Where it is NOT used: Early A0 and A1 models (such as original base M998s, M1038s, etc.) equipped with the 6.2L diesel engine and 3-speed TH400 (3L80) transmission do not have a TPS. The 3-speed transmission uses a vacuum modulator/kickdown switch and governor rather than a computer-controlled electronic TPS.
  • Identifiers/Cross-References:
    • GM Part #: 12554488
    • AM General Part #: 5714530
    • NSN (National Stock Number): 2990-01-426-4425 [1]
    • How Do You Know When It Needs to Be Replaced?
    Because the TPS directly governs transmission behavior, symptoms of a failing or miscalibrated sensor show up in how the vehicle shifts and drives
    Harsh or Erratic Shifting: The transmission may bang into gear abruptly, shift up or down unexpectedly, or refuse to shift at the correct RPM.

    Transmission Limp Mode: A failed signal will cause the TCM to default to a failsafe "limp mode," locking the transmission into 2nd gear with maximum line pressure.

  • No Overdrive or Converter Lockup: The vehicle will fail to shift into 4th gear or engage the torque converter clutch, causing high RPMs at highway speeds.
  • Hesitation or "Dead Spots": As the internal resistive track wears, dead spots cause momentary signal loss when depressing the pedal, confusing the TCM.
  • Failed Multimeter Test: Using a digital multimeter across leads B (signal) and C (ground), the voltage should sweep smoothly from approximately ~0.5V at idleup to ~4.5V at wide-open throttle (WOT) without dropping out or spiking. If it drops to 0V or jumps erratically during the sweep, the sensor track is damaged and needs replacement.
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