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the engine runs smooth. no hesitation and no ruff idel runs great but the service engine soon kicked on today. i retreived the code it was a P0108 Manifold Absolute Pressure/Barometric Pressure Circuit High Input. what i read with this there should be ruff idle amd hesitation. since mine is running fine other then the service engine soon light coming on whats the most likeable cause and fix. i have read mass air sencor bad and bad ecm to what ever whats the most like able cause and fix. since its running fine. thanks. and stay dirty eric ha ha i am.
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What does that mean?
The MAP (Manifold Absolute Pressure) sensor measures engine manifold negative air pressure. It’s usually a three wire sensor: a ground wire, a 5 volt reference wire from the PCM (Powertrain Control Module) to the MAP sensor, and a signal wire that informs the PCM of the MAP sensor voltage reading as it changes. The higher the engine vacuum, the lower the voltage reading. The voltage should range between about 1 volt (at idle) to about 5 volts (WOT wide open throttle).
If the PCM sees the voltage reading from the MAP sensor is greater than 5 Volts, or if the voltage reading is higher than what the PCM considers normal under certain circumstances, a P0108 DTC will set.
Symptoms
Symptoms of a P0108 DTC code may include:
MIL (Malfunction Indicator Lamp) will likely be on
Engine may run poorly
Engine may not run at all
Fuel mileage may decrease
Presence of black smoke at exhaustCauses
Potential causes of a P0108 code:
Bad MAP sensor
Leak in vacuum supply line to MAP sensor
Engine vacuum leak
Short on signal wire to PCM
Short on reference voltage wire from PCM
Open in ground circuit to MAP
Worn engine causing low vacuumPossible Solutions
A good way to diagnose if the MAP sensor is to blame would be to compare the KOEO (key on engine off) MAP sensor reading on a scan tool with the Barometric pressure reading. They should be the same because they both measure atmospheric pressure.
If the MAP reading is greater than 0.5 volt off of the BARO reading, then replacing the MAP sensor would likely fix the problem. Otherwise, start the engine and observe the MAP reading at idle. It should normally be about 1.5 volts (varies according to altitude).
a. If it is, the problem is likely intermittent. Check all the vacuum hoses for damage and replace as necessary. You can also try wiggle testing the harness and connector to reproduce the problem.
b. If the scan tool MAP reading is more than 4.5 volts, check the actual engine vacuum reading with the engine running. If it is less than 15 or 16 in. Hg, then the PCM is probably not seeing enough vacuum (due to a worn engine, perhaps) for a given operating condition (which causes a higher than normal voltage signal to the PCM) and setting the code. Repair the engine vacuum problem and retest.
c. But, if the actual engine vacuum reading is 16 in. Hg or more, then unplug the MAP sensor. The scan tool MAP reading should indicate that there is no voltage present. Check that the ground from the PCM is intact and also that the MAP sensor connector and terminals are tight. If the connection is good, then replace the map sensor.
d. However if, with KOEO, & the MAP sensor unplugged, the scan tool shows a voltage reading, then there may be a short in the harness to the MAP sensor. Turn the ignition off. At the PCM unplug connector and remove the MAP signal wire from the connector. Re-attach the PCM connector and see if with KOEO, the scan tool MAP reading shows voltage. If it still does, replace the PCM. If not, check for voltage on the signal wire you just removed from the PCM. If there is voltage on the signal wire, find the short in the harness and repair.Source : http://www.obd-codes.com/p0108
here is a link for some help.
Ok here’s an update I rescanned I have a p1106 and a p0108 from what I read both the codes kinda go together and it revoles around the map sensor voltage being to high should I replace map sencor or what you think. I’m not seeing nothing broke in wiring plug is clean oh the p1106 from what I read is change in intake manifold vacuum but it kinda ties into that p0108 they say if that code is present to diagnose it first. What you think guys.
High voltage readings usually mean an open somewhere. There may be a connection problem somewhere. If it were me I would first reset the code to see if it comes back. Sometimes just doing this is enough to get rid of the code. Low battery voltage, or other electrical anomalies can cause such things. If the code comes back I might look for an open before replacing the sensor, there could be a wiring issue somewhere that’s causing the code to set. Keep us posted.
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