P2108

Code

HUMMER P — Powertrain

Throttle Actuator Control (TAC) Module Performance

Brand: HUMMER

Type: P — Powertrain

Views: UK: 13 EN: 24 RU: 14

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Page language: EN

Causes

Faulty throttle actuator control (TAC) module / electronic throttle body
Open, shorted, corroded or damaged wiring/connectors between PCM, TAC module and accelerator pedal sensors
Low battery voltage or weak charging system
Faulty accelerator pedal position (APP) sensor(s)
PCM software, calibration, or internal fault
Mechanical binding of throttle plate or carbon buildup preventing movement

Symptoms

Check Engine Light (MIL) illuminated
Reduced engine power / limp-home mode
Erratic idle, surging or stalling
Poor throttle response or no throttle response
Stored multiple throttle-related DTCs
Unusual throttle plate movement or failure to return to idle

What to check

Retrieve all DTCs and freeze frame data with a scan tool; note related codes (APP, TPS, communication)
Verify battery voltage and charging system under load (should be ~12.6V at rest, ~13.5–14.5V running)
Inspect connectors and wiring at throttle body, TAC module and pedal assembly for corrosion, damage or poor pins
Check for proper grounds at engine and PCM
Use scan tool to compare commanded throttle position vs actual throttle position and monitor APP sensor values
Check for CAN/serial bus errors or lost communication events in scanner data

Signal parameters

Accelerator pedal sensor voltages: typically 0.5–4.5 V (two sensor circuits with different slopes); exact values vary by model
Throttle position feedback voltage: typically 0.2–4.8 V depending on position sensor design
Actuator supply voltage: switched 12 V (battery) when commanded; expected near battery voltage under test
Command signal: PWM/duty-cycle or serial command from PCM — duty cycle or commanded position will vary by throttle demand
CAN / communication bus nominal voltage: around 2.5 V idle on each network line; monitor for error frames

Diagnostic algorithm

Capture and record all codes and live data (commanded vs actual throttle, APP sensors, battery voltage, freeze frame).
Verify battery state and charging system; charge battery or perform load test if voltage is low or unstable.
Visually inspect wiring and connectors at the throttle body, TAC module and accelerator pedal for damage, corrosion or loose pins; repair as needed.
With a scan tool, monitor APP sensor voltages while operating the pedal; ensure smooth, correlated changes and no duplicates/crossed signals.
Compare commanded throttle position and actual throttle plate position during various throttle demands. Note any lag, nonlinearity or failure to follow command.
Check actuator power and ground circuits with key on / engine off and while commanding throttle from a scan tool. Verify appropriate supply and ground continuity.
If available, use an oscilloscope to observe PWM command and feedback waveforms for noise, dropouts or abnormal duty cycles.
Inspect throttle plate for mechanical obstruction; clean throttle body if heavy carbon is present and re-test.
Clear codes and perform throttle relearn / adaptation procedure per manufacturer instructions, then retest under road or controlled conditions.
If tests indicate internal TAC module or PCM fault (no valid actuator response, internal diagnostics failing), consider replacement of the throttle body/TAC module and program/relearn as required. Re-scan and verify repairs.
If intermittent or network-related faults persist, investigate CAN/communication wiring and modules on the same bus.

Likely causes

Corroded/damaged connector or wiring to throttle body
Throttle body actuator motor or internal position sensor failure
Failed or out-of-spec accelerator pedal position sensor
Low battery/poor ground affecting actuator performance
Failed TAC module or PCM requiring reflash or replacement

Fault status

⚠️ Status

P2108 — Throttle Actuator Control (TAC) Module Performance: PCM detected performance/discrepancy in throttle actuator control; further diagnosis required.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours

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