P1172

Code

VOLKSWAGEN P — Powertrain

Throttle Actuation Potentiometer Signal 2 Signal Too Low

Brand: VOLKSWAGEN

Type: P — Powertrain

Views: UK: 33 EN: 105 RU: 47

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Page language: EN

Causes

Short to ground in throttle potentiometer #2 signal circuit
Open or high-resistance wiring or connector to the sensor
Failed throttle position potentiometer (internal fault)
Poor reference voltage or ground at the throttle body
Corroded or damaged connector pins or wiring harness
Faulty throttle body assembly or control module (less common)

Symptoms

Check Engine Light (MIL) illuminated
Reduced engine power / limp-home mode
Poor or unpredictable throttle response
Engine may idle poorly or stall in extreme cases
Throttle pedal may feel normal but throttle response is limited

What to check

Read and record freeze frame / live data for both throttle sensors and compare values
Verify battery and charging system voltage (ECM reference must be stable)
Visual inspection of throttle body connector and wiring for damage, corrosion, or moisture
Backprobe the sensor connector with ignition ON (engine OFF) to measure reference, signal, and ground
Scan for additional related DTCs (other throttle/pedal sensor or CAN/communication codes)
Wiggle test wiring while monitoring live data to reproduce fault

Signal parameters

Sensor reference (VREF): typically ~5.0 V (approx. 4.8–5.2 V) with ignition ON
Sensor ground: near 0 V (check for continuity to chassis/ECM ground)
Potentiometer #1 typical output: ~0.5–1.5 V at closed throttle to ~4.0–4.5 V at wide open (varies by model)
Potentiometer #2 typical output: usually inverted to #1 (e.g., ~4.0–4.5 V at closed throttle to ~0.5–1.5 V at wide open) on many VW throttle bodies
Fault threshold (approx): signal below ~0.2–0.4 V often flagged as 'too low' by ECM

Diagnostic algorithm

Retrieve freeze-frame and live data: record sensor #1 and #2 voltages and values at key ON (engine OFF) and at idle/commanded throttle.
Confirm charging/battery voltage stable (12.5–14.5 V). An unstable supply can affect sensors.
Visually inspect connector and wiring to throttle body for damage, corrosion, or water. Repair any obvious issues.
With ignition ON (engine OFF), backprobe the throttle sensor connector: verify VREF ~5 V, signal for pot #2 is measured, and ground is good. If VREF or ground is missing, trace to ECM.
If VREF and ground are correct but signal is low, test for short to ground: disconnect throttle connector and measure continuity between signal pin and chassis ground; low resistance indicates short.
Perform wiggle/pressure tests on wiring from throttle to ECM while monitoring live data to locate intermittent faults.
If wiring and connectors test OK, remove throttle body and bench-test or replace throttle assembly (follow manufacturer procedures).
After repair or replacement, clear codes and perform throttle adaptation / relearn procedure as required by manufacturer, then road-test and recheck for reoccurrence.
If problem persists after wiring and throttle body are verified, consider ECM input circuit failure and evaluate ECM replacement only after confirming upstream wiring/sensor fault is not present.

Likely causes

Damaged/shorted signal wire from throttle potentiometer #2 to ECM
Loose, corroded or bent connector pin at throttle body or engine harness
Failed potentiometer element inside the throttle body (sensor #2)
Loss of ground or 5 V reference to the sensor

Fault status

⚠️ Status

Throttle actuation potentiometer signal 2 voltage below minimum threshold; ECM registers fault and may limit throttle control.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours

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P1172 — Throttle Actuation Potentiometer Signal 2 Signal Too Low