Code
P1108
SATURN
P — Powertrain
BARO To MAP Sensor Circuit Comparison Too High
AI status
Completed
Completed
100%
Causes
- Faulty BARO sensor (internal failure or contamination)
- Faulty MAP sensor
- Short or open in wiring between sensors and PCM (power, ground, signal)
- Poor sensor connector contact or corrosion
- Intake manifold vacuum leak or clogged MAP reference port
- Sensor reference voltage (5V) loss or poor ground
Symptoms
- MIL (check engine light) illuminated
- Possible rough idle, hesitation or reduced drivability under load
- Abnormal fuel trim values (high or unstable long/short-term trims)
- Hard starting or poor cold start behavior (if module uses BARO for trim)
- Decreased fuel economy
What to check
- Retrieve freeze frame and live data: compare BARO and MAP sensor readings with key ON engine OFF and at idle
- Visual inspection of sensor connectors, wiring, and vacuum hoses for damage or contamination
- Backprobe sensor connector and verify reference voltage (typically ~5 V) and ground
- Measure sensor output voltages or kPa readings at known conditions (key ON, engine OFF = ambient pressure)
- Check for intake vacuum leaks and blocked MAP port/lines
- Wiggle wiring harness while monitoring live data for intermittent faults
Signal parameters
- Both BARO and MAP typically share a 5 V reference and ground
- Sensor outputs commonly range ~0.5–4.5 V corresponding to low–high pressure (varies by sensor)
- Ambient pressure at sea level ~101 kPa (BARO reading should approximate MAP with engine off/doors closed)
- Typical correlation threshold: sensors should agree within a small margin (often ~0.2–0.5 V or ~5–15 kPa); larger differences can trigger the code
Diagnostic algorithm
- Read and record freeze frame data and live sensor values (BARO and MAP). Note conditions when code set.
- With ignition ON engine OFF, verify BARO and MAP outputs — they should match or be very close (ambient pressure). If BARO is high relative to MAP, proceed.
- Inspect connectors, wiring, and MAP vacuum/vent hoses for damage, kinks or contamination; repair as needed.
- Backprobe each sensor: verify 5 V reference present, good ground, and sensor output voltage. Compare outputs to expected ambient values.
- If wiring and reference are good but one sensor output is out of expected range, disconnect sensor(s) and measure resistance if service info available or substitute a known-good sensor to confirm.
- Check intake for vacuum leaks and verify MAP port is clear (blow through hoses carefully or visually inspect).
- If sensors and wiring test good, inspect PCM connector pins for corrosion or damage and consider PCM diagnostic/repair per manufacturer guidance.
- Clear codes and perform road/idle test to confirm repair. If intermittent, perform wiggle/stress tests while monitoring data to reproduce.
Likely causes
- Damaged or contaminated BARO sensor
- MAP sensor fault or clogged vent/reference hose
- Wiring short to power on BARO signal (raising BARO vs MAP)
- Open/poor ground for sensors or intermittent connector contact
- Intake leak causing MAP lower than BARO (while BARO reads ambient)
Fault status
Status
BARO to MAP sensor circuit comparison too high — BARO and MAP sensor readings differ beyond allowed limits; MIL set.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email