OBD-II trouble code
P0108: Manifold Absolute Pressure/Barometric Pressure Circuit High Input
SAE J2012 names a high manifold-absolute-pressure or barometric-pressure input. On 2008 GM GRP09 the fail is above 4.85 volts. On the 2004 L61 file it is above 3.80 volts at low throttle and under 1 mph.
Quick facts
- System
- Powertrain
- Category
- Fuel & Air Metering
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $450
- DIY difficulty
- Intermediate DIY
Browse every code in P0100–P0199, or start from the full code library.
What does P0108 mean?
P0108 is Manifold Absolute Pressure/Barometric Pressure Circuit High Input in SAE J2012 APR2002. High means the module pin is above that manufacturer's range. On a voltage MAP sensor the top of the normal scale is already a high pressure, near atmospheric, so a code threshold has to sit above a legitimate wide-open-throttle reading. The charts do not put that threshold in the same place.
GM's 2008 GRP09 sheet says P0108 detects a MAP output out of range high, or a continuous short to high in the signal circuit or the MAP sensor. The threshold is MAP voltage over 97 percent of the 5-volt reference, written as 4.85 volts. The count is 320 failures out of 400 samples, one sample each 12.5 ms. Type B. The only enable words on that cell are that the MAP sensor has deadbands. This page does not add rpm or temperature gates the cell does not state.
The 2004 GM file 2004file2_L61 titles it Manifold Pressure Too High: a continuous short to voltage or a signal out of range high. The threshold is MAP over 3.80 volts, also stated as 82 kPa. It runs only when throttle is under 12 percent, vehicle speed is under 1 mph, and engine run time is past a 20–40 second window. P0122 and P0123 must not be set. The count is 80 failures out of 100, every 125 ms. Type B. A reading of 3.80 volts can be a plausible pressure on another calibration and is already a fail on this one, at idle, in park, after the run-time delay.
The 1999 Ford PCED titles P0108 BARO Sensor High Voltage Detected. Causes are the reference shorted to VPWR, the BARO signal shorted to VPWR, a damaged BARO sensor, and a damaged PCM. The aide says reference voltage should be less than 6.0 volts and that the PID is a frequency. It does not use 4.85 volts or 3.80 volts.
A MAP hose that has come off can hold the reading near atmospheric while the engine idles. On the L61 file that shows up as a voltage already over 3.80 volts with the throttle closed and the vehicle stopped. On GRP09 the electrical fail is higher, over 4.85 volts, which is above a normal atmospheric reading on a 5-volt sensor. A hose-off diagnosis and a short-to-voltage diagnosis are not the same test.
Common causes
- On GRP09, a short to high in the MAP signal or the sensor, once voltage is over 4.85 volts
- On the 2004 L61 file, a short to voltage or an out-of-range-high signal over 3.80 volts (82 kPa) with throttle under 12 percent and speed under 1 mph
- On that L61 enable, a manifold hose or port that leaves MAP near atmospheric at closed throttle, because 82 kPa already fails the test
- On the 1999 Ford PCED, reference or BARO signal shorted to VPWR
- A damaged sensor or PCM after the short-to-voltage test in the chart has passed
Symptoms
- Malfunction indicator lamp with P0108
- On GRP09, MAP voltage over 4.85 volts
- On the L61 file, MAP over 3.80 volts after 20–40 seconds of run time, throttle under 12 percent, speed under 1 mph
- On the 1999 Ford PCED, a frequency BARO PID above the calibrated maximum, with a reference that should be under 6.0 volts
- The GRP09 wording is a short to high, not a description of a rich idle
Diagnostic steps
- 1.Pick the threshold from the matching chart. Over 4.85 volts is GRP09. Over 3.80 volts at the L61 speed and throttle gates is the 2004 L61 file. The 1999 Ford PCED is a frequency BARO sensor whose reference should be under 6.0 volts.
- 2.On the L61 file, do not call a high reading a failure unless throttle is under 12 percent, speed is under 1 mph, and run time is past the 20–40 second window. If P0122 or P0123 is stored, repair that code first. The test is inhibited.
- 3.With the engine at the enable condition, compare the live MAP voltage with the threshold. Then ignition off, disconnect the sensor. Key on, measure the signal pin. If the chart says an open signal should fall to the low end and the pin stays at reference voltage, the wire is shorted to the reference or to another source. Many inputs are biased, so use the open-circuit voltage that chart prints rather than assuming the pin falls to zero.
- 4.On GRP09, a voltage over 4.85 volts is the short-to-high test. A reading that sits near atmospheric at idle but under 4.85 volts has not reached this GRP09 threshold. Look at P0106 on that sheet before replacing the sensor for a stuck-at-atmosphere reading.
- 5.On the L61 file, because 82 kPa already fails at closed throttle, inspect the manifold port and the hose for a disconnect or a split before replacing the sensor. That inspection is not the GRP09 4.85-volt test.
- 6.On the 1999 Ford PCED, check the reference for a short to VPWR and the BARO signal for a short to VPWR. Reference voltage should be less than 6.0 volts. Do not substitute a 4.85-volt MAP limit.
- 7.Replace the sensor only after the short-to-voltage test and, where the chart includes it, the hose inspection have not found the high reading. Clear the code and recheck at the same enable condition. Do not use a wide-open-throttle pull on a public road as the proof.
Repair cost
$100 – $450
An accessible MAP sensor is about $100 to $140 installed, and a Camry-class sensor is about $400 to $450. The chart also has the manifold hose checked before the sensor is bought.
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Related repairs
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.