Code
P1122
MINI
P — Powertrain
Accelerator pedal position (APP) sensor 1 - low input
Views:
UK: 1
EN: 3
RU: 2
AI status
Completed
Completed
100%
Causes
- Damaged, corroded, or disconnected harness/connector to APP sensor 1
- Short to ground on the sensor 1 signal wire
- Open or high-resistance signal wire between pedal and ECU
- Faulty APP sensor (pedal assembly)
- Loss of reference 5V supply or ground to the sensor
- ECU input circuit fault
Symptoms
- Check Engine MIL illuminated
- Reduced engine power / limp mode or throttle derate
- Unresponsive or inconsistent throttle response
- Hesitation on acceleration or inability to accelerate
- Stored related throttle/pedal codes and possibly other APP/TP sensor codes
What to check
- Scan for all stored codes and freeze frame data; note any related throttle or CAN faults
- Visually inspect pedal assembly connector and wiring for damage, corrosion, or pin push-out
- Backprobe APP sensor 1 signal, 5V reference, and ground with key ON (engine off) and record voltages
- Compare APP sensor 1 signal to APP sensor 2 (if present) and observe live data while depressing pedal
- Check continuity and for short-to-ground on the signal wire between pedal connector and ECU with key OFF
- Wiggle test harness while monitoring live data to detect intermittent faults
Signal parameters
- Reference supply (5V) present at sensor with key ON; typical ~4.8–5.2 V
- Sensor ground near 0 V
- APP sensor 1 output typically varies across pedal travel (approx. 0.2–4.5 V depending on design); 'low input' usually < ~0.2–0.5 V
- APP sensor 1 and sensor 2 should show correlated increasing voltages with pedal travel; absolute values and slope depend on the vehicle
Diagnostic algorithm
- Retrieve freeze frame and all DTCs. Note whether code is continuous or intermittent.
- Perform a visual inspection of the pedal module harness and connector for damage, moisture, or corrosion. Repair any obvious issues and retest.
- With the key ON (engine off) backprobe the pedal connector: verify 5V reference, ground, and APP1 signal voltage. If reference or ground missing, trace to power/ground source and repair.
- Compare APP1 signal to APP2 (if present) on a scan tool while slowly depressing the pedal. Look for expected change in voltage and correct correlation between sensors.
- If APP1 is stuck low, disconnect the pedal connector and check signal wire continuity to the ECU. Check for short to ground on the signal wire using an ohmmeter.
- Repair any wiring faults (replace damaged section, repair connector pins). After repairs, clear codes and verify proper live data behavior.
- If wiring and power/ground are good but APP1 remains low, replace the accelerator pedal module/sensor assembly and re-check.
- If replacement does not clear the issue, test/inspect the ECU input for that channel or consult manufacturer service information for ECU bench tests.
- After repair, perform throttle adaptation/relearn procedures if required by the manufacturer, then road-test and confirm the fault is cleared.
Likely causes
- Wiring damage at pedal harness (rubbed through, pinched, or broken)
- Corroded or loose connector pins at pedal or ECU
- Failed pedal position sensor 1 inside accelerator pedal module
- Short to ground in signal circuit
- Poor ground or missing 5V reference supply
Fault status
Status
APP sensor 1 signal below expected threshold. Possible wiring short to ground, missing 5V reference/ground, or failed pedal sensor. Causes throttle response issues and may trigger limp-home mode.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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