Code
P1108
ACURA
P — Powertrain
BARO Circuit High Input
AI status
Completed
Completed
100%
Causes
- Faulty BARO/barometric pressure sensor
- Short to battery/reference voltage in sensor signal circuit
- Open or high-resistance ground or reference supply
- Corroded, damaged, or disconnected connector/wiring harness
- Blocked or contaminated sensor vent/port
- Faulty ECM (less common)
Symptoms
- Check Engine Light (MIL) illuminated
- Reduced engine performance or poor drivability
- Hard starting or rough idle (depending on other inputs)
- Reduced fuel economy
- Unusual fuel trim/engine management behavior
What to check
- Read and record freeze-frame and live data for BARO, MAP and related sensors.
- Visual inspection of BARO sensor, wiring, and connector for damage, corrosion, or loose pins.
- Compare BARO reading to MAP with key ON / engine OFF — they should be nearly equal (both = ambient pressure).
- Backprobe and measure sensor signal voltage and reference voltage at key ON and running.
- Wiggle test harness while monitoring live data to reproduce fault.
- Disconnect sensor (if safe) to see if code changes or MIL behavior changes.
Signal parameters
- Key ON / Engine OFF: BARO should equal MAP and ambient pressure (sensor voltage typically in nominal sensor range — varies by model).
- Typical BARO sensor voltage range: approximately 0.5–4.5 V (varies by vehicle).
- A sustained higher-than-expected BARO voltage or value compared with ambient/MAP triggers P1108.
- Reference supply usually 5V (check manufacturer spec) and good ground required.
Diagnostic algorithm
- Retrieve freeze-frame and live data. Confirm code is current and note conditions when set.
- Visually inspect sensor and harness for damage, corrosion, or water contamination.
- With a digital meter, verify reference voltage (5V) and ground at the BARO connector with key ON.
- Measure BARO signal voltage with key ON/engine OFF and compare to ambient/MAP reading. BARO should match MAP at this condition.
- If BARO signal is higher than MAP/ambient, inspect wiring for short to power. Repair any damaged wiring or connectors.
- Perform wiggle/connector tap test while monitoring signal to locate intermittent faults.
- If wiring and connector are good, substitute a known-good BARO sensor or bench-test replacement to verify sensor operation.
- Clear codes and test drive to confirm repair. If code returns after sensor and wiring verified, consider ECM diagnosis/repair per manufacturer guidance.
Likely causes
- Sensor internal failure causing excessive output voltage
- Signal wire shorted to 5V/ignition voltage
- Poor connector ground or 5V reference instability
- Sensor vent clogged or exposed to boost (if not intended)
- Intermittent wiring fault or corrosion at connector pins
Fault status
Status
BARO Circuit High Input — BARO sensor signal above expected range or inconsistent with ambient/MAP; possible sensor or wiring fault.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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