Powertrain
Manufacturer-specific
OBD-II Fault Code
P1111: Intake Air Temperature (IAT) Sensor Circuit Intermittent High Voltage
Meaning, symptoms, likely causes, diagnostic checks and repair guidance for P1111.
Power supply / charging
Use this category to narrow your checks before replacing parts.
High
Severity is a general guide. Confirm with scan-tool data and vehicle symptoms.
What P1111 usually means
Intake Air Temperature (IAT) Sensor Circuit Intermittent High Voltage.
Common symptoms
Check Engine light; Poor drivability or reduced fuel economy depending on fault
Likely causes
Weak battery; Charging system fault; Loose/corroded terminals; Poor ground; High signal voltage; Open ground; Short to voltage; Failed sensor; Loose connector; Moisture/corrosion; Harness vibration fault
Diagnostic checks
Scan all modules and record freeze-frame data before clearing codes; Check battery voltage and related fuses; Test battery state of charge and charging voltage; Inspect terminals and ground straps; Check sensor ground and signal circuit for short to voltage; Wiggle-test harness while watching live data; Inspect for water intrusion/corrosion
Repair guidance
Clean/tighten terminals, replace weak battery, repair alternator/charging circuit as needed; Repair ground/signal circuit or replace confirmed faulty sensor; Clean/secure connector and repair damaged harness
Verification after repair
Clear code, road-test through the same drive condition, then rescan