Code
P1108
OLDSMOBILE
P — Powertrain
BARO To MAP Sensor Circuit Comparison Too High
AI status
Completed
Completed
100%
Causes
- Faulty MAP sensor
- Faulty BARO sensor or malfunctioning BARO circuit
- Leaking, collapsed, missing or disconnected MAP vacuum hose or intake leak
- Wiring problems: short to voltage/ground, open, high resistance or poor connector
- Contaminated or clogged MAP sensor port
- PCM (engine control module) input circuit fault or internal failure
Symptoms
- Check Engine Light (MIL) illuminated
- Reduced engine performance or hesitations
- Rough idle or stalling at idle
- Poor drivability under load
- Possible hard starting in extreme cases
What to check
- Retrieve DTC and freeze-frame data with a scan tool
- Compare live BARO and MAP sensor values (key-on engine-off, at idle, and under load)
- Visually inspect MAP sensor, BARO sensor (if separate), connectors and wiring for damage or corrosion
- Inspect MAP vacuum hose and intake manifold for leaks, cracks or disconnection
- Perform wiggle tests on harness while monitoring live data for intermittent faults
- Check for related stored codes (MAP, MAF, vacuum system codes)
Signal parameters
- Key ON engine OFF: BARO and MAP should be nearly equal (within sensor tolerance)
- At idle: MAP should read lower than BARO (vacuum present); BARO should remain near ambient and vary only with altitude/temperature
- Typical MAP/BARO voltage span (vehicle dependent): roughly 0.2–4.8 V depending on pressure; check factory specs for exact numbers
- When applying vacuum to MAP sensor, MAP voltage should change smoothly and correspond to pressure change
Diagnostic algorithm
- Connect a scan tool, record freeze-frame and live BARO and MAP values at key‑on engine‑off, idle and during load. Note when discrepancy occurs.
- Visually inspect MAP and BARO connectors and wiring; repair any damaged insulation, pins or corrosion.
- Check MAP vacuum hose and intake for leaks. Smoke-test intake system if available. Repair any leaks and re-test.
- With engine off, compare BARO and MAP at key‑on: if they differ significantly, suspect BARO or wiring. If they match at key‑on but diverge under engine operation, suspect MAP sensor, vacuum leak, or harness.
- Backprobe MAP sensor and measure voltage (or use a lab scope) while applying known vacuum: signal should move smoothly and within spec. Verify sensor reference 5V and ground circuits are good.
- If wiring and vacuum path are good but sensor signal is incorrect, swap with a known-good MAP (or BARO if separate) per manufacturer procedure and re-test.
- Clear codes and perform a road test to verify resolution. If code returns, consider PCM input circuitry as last resort and consult technical service info.
- If intermittent, perform wiggle tests and monitor live data to capture transient faults.
Likely causes
- MAP sensor signal lower than expected due to vacuum leak or failed sensor
- Damaged or corroded connector/wiring between MAP/BARO and PCM
- BARO sensor reporting incorrectly high (less common)
Fault status
Status
BARO-to-MAP sensor comparison out of range — BARO reading higher than MAP beyond allowed tolerance. Inspect MAP/BARO sensors, vacuum/ intake system, wiring and connectors.
Repair difficulty: Medium
Diagnostic time: 0.5 - 2.0 hours
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