P0069 Manifold Absolute Pressure – Barometric Pressure Correlation
P0069 – Manifold absolute pressure (MAP) sensor/barometric pressure (BARO) sensor correlation
By Mia Bevacqua
ASE Master Tech
Trouble Code Fault Location Probable Cause P0069 Manifold absolute pressure (MAP) sensor/barometric pressure (BARO) sensor correlation MAP sensor, mechanical fault
By Mia BevacquaASE Master Tech
| Trouble Code | Fault Location | Probable Cause |
|---|---|---|
| P0069 | Manifold absolute pressure (MAP) sensor/barometric pressure (BARO) sensor correlation | MAP sensor, mechanical fault |
What Does P0069 Mean?
The manifold absolute pressure (MAP) sensor is used to measure engine load. The powertrain control module (PCM) sends the MAP sensor a reference voltage and the sensor varies the voltage according to manifold vacuum. The PCM then uses this information to adjust ignition timing and fuel delivery.
An example of a MAP sensor
(Courtesy: autozone.com)
Vacuum and pressure are inversely proportional (when vacuum goes up, pressure goes down). Because of this, the MAP sensor is able to measure the pressure in the intake manifold to gauge vacuum. Manifold vacuum is a good indicator of engine load. With the engine off, manifold pressure and atmospheric (barometric) pressure are the same. With the engine running, the movement of the pistons and restriction of the throttle plates create vacuum (reduce pressure). When the engine is under heavy load at wide open throttle (WOT), vacuum is nearly zero. At this time, engine pressure and atmospheric pressure are almost the same.
Depending on the elevation, barometric pressure is usually between 28 to 31 inches of mercury (Hg). By comparison, engine vacuum at sea level is between 17-22 in-Hg. This drops approximately 1 in-Hg for every 1000 ft. of elevation. On some vehicles, when the engine is first started, the PCM looks at the MAP sensor to determine barometric pressure. There are other vehicles, however, that use a dedicated BARO sensor. Others still use a combination BMAP sensor.
There are two types of MAP sensors: analog and frequency. The analog type uses a diaphragm and is connected to the intake manifold by a vacuum line. The sensor monitors the movement of the diaphragm and sends a corresponding analog signal back to the PCM. This type of sensor will have three wires: reference, signal and ground. The other type of MAP sensor is the digital, or frequency type, which produces a digital voltage signal instead of an analog signal.
A cut away of an analog MAP sensor
(Courtesy: autozone.com)
As was mentioned, some vehicles use an independent BARO sensor. These devices are designed to measure only barometric pressure. The BARO sensor is similar to the MAP sensor in design but is more sensitive to changes in atmospheric pressure.
The code P0069 stands for manifold pressure/barometric pressure correlation. The PCM compares BARO sensor and MAP readings at idle. If the difference between the two is greater than specified, the PCM will set a diagnostic trouble code (DTC).
Symptoms
The most common symptom, of course, is an illuminated check engine light. Other symptoms may include surging, rough idle, detonation and loss of power.
Troubleshooting
The following steps will help you diagnose a code P0069:
- Visually inspect the sensors and wiring
The first step is to visually inspect the MAP sensor, its connector and wiring. If the vehicle uses a dedicated BARO sensor you’ll want to inspect that too. Look for corrosion, broken wiring, loose connections, etc. Also check the vacuum line to the sensor for cracks.
- Check MAP sensor operation
Testing the MAP sensor varies depending on which type of sensor you have. This can be determined by measuring the signal voltage; if it never changes from 2.5 volts, the sensor is most likely a frequency type.
- Analog MAP sensor
Analog MAP sensors can be tested with a digital multimeter (DMM) and a handheld vacuum pump. Leave the electrical portion of the MAP sensor connected and disconnect the MAP sensor vacuum hose. Attach the handheld vacuum pump to the MAP sensor nipple.
Next, back probe the MAP sensor signal wire with the red DMM lead and touch the black lead to ground. Pump the vacuum pump while simultaneously watching the DMM. Generally, voltage should decrease as vacuum increases. Consult the manufacturer’s repair information for exact specifications.
Alternately, you can test MAP sensor operation on the vehicle. Back probe the MAP sensor connector with the red meter lead and touch the black meter lead to ground. Turn the ignition key on; the DMM should generally read between 4.6 to 5.0 volts. Next, start the engine and let it idle. The MAP sensors voltage reading should drop to approximately 1 to 2 volts. These readings will vary slightly depending on the altitude. The manufacture’s repair information should be consulted for the exact specifications.
- Digital MAP sensor
Digital MAP sensors can be tested with a digital multimeter (DMM) and a handheld vacuum pump. Leave the electrical portion of the MAP sensor connected and disconnect the MAP sensor vacuum hose. Attach the handheld vacuum pump to the MAP sensor nipple.
Next, back probe the MAP sensor signal wire with the red DMM lead and touch the black lead to ground. Set your meter to the frequency (Hz) setting. Pump the vacuum pump while simultaneously watching the DMM. The frequency should change in regard to the change in vacuum (in most cases Hz will decrease as vacuum increases). Consult the manufacturer’s repair information for exact specifications.
Digital MAP sensor operation is bested with an oscilloscope if one is available. Back probe the MAP sensor connector with the red meter lead and touch the black meter lead to ground. This way the sensors voltage can be read directly. If the sensor is working properly, the voltage signal should change in response to change in manifold vacuum.
Testing digital MAP sensor
(Courtesy: riboparts.com)
- Check the MAP sensor circuit
There should be three wires going to the MAP sensor regardless of whether you’re testing an analog or digital sensor. As was stated earlier, these wires are signal, reference and ground. Start by consulting the wiring diagram for your vehicle to determine which pin on the connector is which. Next, connect the red DMM lead to the battery positive terminal and the black lead to the ground pin. You should see a reading of about 12 volts indicating a good ground. Then, check that the 5-volt reference is getting to the sensor by connecting the red DMM lead to the reference voltage pin and the other to ground. You should see a reading of about 5 volts indicating a good reference voltage. Finally, check that there is continuity to the PCM. You can do this by touching one meter lead to the return signal pin on the sensor connector and the other to signal pin on the PCM. Set your meter to the ohms setting – you should see a value appear on the screen. If instead, your meter read OL, you have an open circuit and will need to trace the factory wiring diagram.
An example of a MAP sensor circuit
(Courtesy: alldata.com)
- Check the BARO sensor circuit (if equipped)
If the vehicle you’re testing includes a separate BARO sensor, it can be tested in the same fashion as the MAP sensor. Follow the MAP sensor and circuit testing procedures outline above for BARO sensor testing.
Common Causes
- MAP sensor circuit problem
- BARO sensor circuit problem
- Faulty MAP sensor
- Faulty BARO sensor
- Faulty PCM
Related Codes
BAT Team Discussions for P0069
- 2005 Stratus Coupe throwing codes and Service Engine light...
Ok...just the other day my car started throwing a 'Service Engine Soon' light and I got it read at AutoZone and they came up with a P0108 and P0069 code that was firing the light. Any help on this would be great. I do have a cold air intake and it never had this problem until recently! I had recentl...
Ok...just the other day my car started throwing a 'Service Engine Soon' light and I got it read at AutoZone and they came up with a P0108 and P0069 code that was firing the light. Any help on this would be great. I do have a cold air intake and it never had this problem until recently! I had recentl...
To find the right fix, begin your diagnosis at the air intake. Open the air box and look for blockages. A dirty air filter can trigger this code, but so could a blockage further into the intake (so be sure to trace airflow from the airbox all the way to the intake manifold). Many times, simply replacing the filter and clearing the code will resolve a P0069 in your Dodge.
However, if no problems are found and a new air filter does not do the job, then the problem is very likely in the IAT (intake air temperature) sensor.
The IAT sensor is located on the intake, and it records the temperature of the air coming into the intake manifold. If this sensor becomes faulty, it can trigger a MAP BPC and a P0069 trouble code. Replacing the IAT sensor is a relatively simple and straight-forward job, and fortunately the parts are not expensive.
NOTE: P0069 and other codes can also be triggered when an after-market chipset has been installed on a Cummins engine computer. This can cause a short or default in the system, setting off codes like P0069. If your Dodge has after-market chips installed, and if your air filter seems clean, you might try diagnosing this code by first uninstalling the non-OEM chips and resetting the system.
If you find your after-market chip is the cause of the problem, it might make sense to remove it permanently. While some after-market programmers and tools can add real power to your diesel, cheap products that promise big horsepower gains for less than $100 should probably be avoided.
After all, if the after-market could figure out a way to boost horsepower by adding a really cheap computer chip to your diesel, don't you think Dodge or Ram would be putting these chips on at the factory?
IN other words, if it seems too good to be true, it probably is.
Author Jason Lancaster is the editor of ExhaustVideos.com, a website that helps vehicle owners find the best after-market exhaust system. Jason also works with WeRMopar.com, a website that offers discounted OEM Dodge Parts online – click herefor more info.
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Manifold Absolute Pressure MAP Sensors
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The Manifold Absolute Pressure (MAP) sensor is a key sensor because it senses engine load. The sensor generates a signal that is proportional to the amount of vacuum in the intake manifold. The engine computer then uses this information to adjust ignition timing and fuel enrichment.
When the engine is working hard, intake vacuum drops as the throttle opens wide. The engine sucks in more air, which requires more fuel to keep the air/fuel ratio in balance. In fact, when the computer reads a heavy load signal from the MAP sensor, it usually makes the fuel mixture go slightly richer than normal so the engine can produce more power. At the same time, the computer will retard (back off) ignition timing slightly to prevent detonation (spark knock) that can damage the engine and hurt performance.
When conditions change and the vehicle is cruising along under light load, coasting or decelerating, less power is needed from the engine. The throttle is not open very wide or may be closed causing intake vacuum to increase. The MAP sensor senses this and the computer responds by leaning out the fuel mixture to reduce fuel consumption and advances ignition timing to squeeze a little more fuel economy out of the engine.
. .
Typical MAP sensor outputs for an older GM application.
HOW A MAP SENSOR WORKS
MAP sensors are called manifold absolute pressure sensors rather than intake vacuum sensors because they measure the pressure (or lack thereof) inside the intake manifold. When the engine is not running, the pressure inside the intake manifold is the same as the outside barometric pressure. When the engine starts, vacuum is created inside the manifold by the pumping action of the pistons and the restriction created by the throttle plates. At full open throttle with the engine running, intake vacuum drops to almost zero and pressure inside the intake manifold once again nearly equals the outside barometric pressure.
Barometric pressure typically varies from 28 to 31 inches of Mercury (Hg) depending on your location and climate conditions. Higher elevations have lower air pressure than areas next to the ocean or someplace like Death Valley, California, which is actually below sea level. In pounds per square inch, the atmosphere exerts 14.7 PSI at sea level on average.
The vacuum inside an engine's intake manifold, by comparison, can range from zero up to 22 inches Hg or more depending on operating conditions. Vacuum at idle is always high and typically ranges from 16 to 20 inches Hg in most vehicles. The highest level of vacuum occurs when decelerating with the throttle closed. The pistons are trying to suck in air but the closed throttle chokes off the air supply creating a high vacuum inside the intake manifold (typically four to five inches Hg higher than at idle). When the throttle is suddenly opened, as when accelerating hard, the engine sucks in a big gulp of air and vacuum plummets to zero. Vacuum then slowly climbs back up as the throttle closes.
When the ignition key is first turned on, the powertrain control module (PCM) looks at the MAP sensor reading before the engine starts to determine the atmospheric (barometric) pressure. So in effect, the MAP sensor can serve double duty as a BARO sensor. The PCM then uses this information to adjust the air/fuel mixture to compensate for changes in air pressure due to elevation and/or weather. Some vehicles use a separate "baro" sensor for this purpose, while others use a combination sensor that measures both called a BMAP sensor.
On turbocharged and supercharged engines, the situation is a little more complicated because under boost there may actually be positive pressure in the intake manifold. But the MAP sensor doesn't care because it just monitors the absolute pressure inside the intake manifold.
On engines with a "speed-density" electronic fuel injection system, airflow is estimated rather than measured directly with an airflow sensor. The computer looks at the MAPsensor signal along with engine rpm, throttle position, coolant temperature and ambient air temperature to estimate how much air is entering the engine. The computer may also take into account the oxygen sensor rich/lean signal and the position of the EGR valve, too, before making the required air/fuel mixture corrections to keep everything in balance. This approach to fuel management isn't as precise as systems that use a vane or mass airflow sensor to measure actual airflow, but it is not as complex or as costly either.
Another advantage of speed-density EFI systems is that they are less sensitive to vacuum leaks. Any air that leaks into an engine on the back side an airflow sensor is "un-metered" air and really messes up the fine balance that's needed to maintain an accurate air/fuel mixture. In a speed-density system, the MAP sensor will detect the slight drop in vacuum caused by the air leak and the computer will compensate by adding more fuel.
On many GM engines that have a mass airflow sensor (MAF), a MAP sensor is also used as a backup in case the airflow signal is lost, and to monitor the operation of the EGR valve. No change in the MAP sensor signal when the EGR valve is commanded to open would indicate a problem with the EGR system and set a fault code.
ANALOG MAP SENSORS
The MAP sensor consists of two chambers separated by a flexible diaphragm. One chamber is the "reference air" (which may be sealed or vented to the outside air), and the other is the vacuum chamber which is connected to the intake manifold on the engine by a rubber hose or direct connection. The MAP sensor may be mounted on the firewall, inner fender or intake manifold.
A pressure sensitive electronic circuit inside the MAP sensor monitors the movement of the diaphragm and generates a voltage signal that changes in proportion to pressure. This produces an analog voltage signal that typically ranges from 1 to 5 volts.
Analog MAP sensors have a three-wire connector: ground, a 5-volt reference signal from the computer and the return signal. The output voltage usually increases when the throttle is opened and vacuum drops. A MAP sensor that reads 1 or 2 volts at idle may read 4.5 volts to 5 volts at wide open throttle. Output generally changes about 0.7 to 1.0 volts for every 5 inches Hg of change in vacuum.
FORD DIGITAL MAP SENSORS
Ford BP/MAP sensors (barometric pressure/manifold absolute pressure) also measure load but produce a digital frequency signal rather than an analog voltage signal. This type of sensor has additional circuitry that creates a 5 volt "square wave" (on-off) voltage signal. The signal increases in frequency as vacuum drops.
At idle or when decelerating, vacuum is high and the BP/MAP sensor output may drop to 100 Hz (Hertz, or cycles per second) or less. At wide open throttle when there is almost no vacuum in the intake manifold, the sensor's output may jump to 150 Hz or higher. At zero vacuum (atmospheric pressure), a Ford BP/MAP sensor should read 159 Hz.
MAP SENSOR DRIVABILITY SYMPTOMS
Anything that interferes with the MAP sensor's ability to monitor the pressure differential may upset the fuel mixture and ignition timing. This includes a problem with the MAPsensor itself, grounds or opens in the sensor wiring circuit, and/or vacuum leaks in the intake manifold (airflow sensor systems) or hose that connects the sensor to the engine.
Typical driveability symptoms that may be MAP related include:
* Surging.
* Rough idle.
* A rich fuel condition, which may cause spark plug fouling.
* Detonation due to too much spark advance and a lean fuel ratio.
* Loss of power and/or fuel economy due to retarded timing and an excessively rich fuel ratio.
A vacuum leak will reduce intake vacuum and cause the MAP sensor to indicate a higher than normal load on the engine. The computer will try to compensate by richening the fuel mixture and retarding timing -- which hurts fuel economy, performance and emissions.
MAP SENSOR CHECKS
First, make sure engine manifold vacuum is within specifications at idle. If vacuum is unusually low due to a vacuum leak, retarded ignition timing, an exhaust restriction (clogged converter), or an EGR leak (EGR valve not closing at idle).
A low intake vacuum reading or excessive backpressure in the exhaust system can trick the MAP sensor into indicating there is a load on the engine. This may result in a rich fuel condition.
A restriction in the air intake (such as a plugged air filter), on the other hand, may produce higher than normal vacuum readings. This would result in a load low indication from the MAP sensor and possibly a lean fuel condition.
A good MAP sensor should read barometric air pressure when the key is turned on before the engine starts. This value can be read on a scan tool and should be compared to the actual barometric pressure reading to see if they match. Your local weather channel or website should be able to tell you the current barometric pressure reading.
Check the sensor's vacuum hose for kinks or leaks. Then use a hand-held vacuum pump to check the sensor itself for leaks. The sensor should hold vacuum. Any leakage calls for replacement.
An outright failure of the MAP sensor, loss of the sensor signal due to a wiring problem, or a sensor signal that is outside the normal voltage or frequency range will usually set a diagnostic trouble code (DTC) and turn on the Check Engine light.
MAP SENSOR SCAN TOOL CHECKS
On 1995 and newer vehicles with OBD II self-diagnostics, a DTC code P0105 to P0109 would indicate a fault in the MAP sensor circuit.
P0105....Manifold Absolute Pressure/Barometric Pressure Circuit
P0106....Manifold Absolute Pressure/Baro Pressure out of range
P0107....Manifold Absolute Pressure/Baro Pressure Low Input
P0108....Manifold Absolute Pressure/Baro Pressure High Input
P0109....Manifold Absolute Pressure/Baro Pressure Circuit Intermittent
P0106....Manifold Absolute Pressure/Baro Pressure out of range
P0107....Manifold Absolute Pressure/Baro Pressure Low Input
P0108....Manifold Absolute Pressure/Baro Pressure High Input
P0109....Manifold Absolute Pressure/Baro Pressure Circuit Intermittent
On older pre-OBD II vehicles, the MAP codes are:
* General Motors: Codes 34, 33, 31
* Ford: Codes 22, 72
* Chrysler: Codes 13, 14
On vehicles that provide data stream through a diagnostic connector and allow a scan tool to display sensor values, the MAP sensor's output voltage can be read and compared to specifications. Basically, you want to see a quick and dramatic change in the MAP sensor signal when the throttle on an idling engine is snapped open and shut. No change would indicate a sensor or wiring fault.
If the sensor is reading low or there is no reading at all, check for proper reference voltage to the sensor. It should be very close to 5 volts. Also check the ground connection. If the reference voltage is low, check the wiring harness and connector for looseness, damage or corrosion.
Scan tools that display OBD II data will also display a "calculated load value" that can be used to determine if the MAP sensor is working or not. The load value is computed using inputs from the MAP sensor, TPS sensor, airflow sensor and engine speed. The value should be low at idle, and high when the engine is under load. No change in the value, or a higher than normal reading at idle might indicate a problem with the MAP sensor, TPS sensor or airflow sensor.
If you display the MAP sensor output on a Digital Storage Oscilloscope (DSO), this is
what the waveform might look like as the throttle position, engine load and speed change.
MAP SENSOR TESTS
A MAP sensor can also be bench tested by applying vacuum to the vacuum port with a hand vacuum pump. With 5 volts to the reference wire, the output voltage of an analog MAP sensor should drop, and on a Ford digital MAP sensor the frequency should increase.
An analog MAP sensor's voltage can also be read directly using a voltmeter or oscilloscope. A digital MAP sensor's frequency signal can be read with a DVOM if it has a frequency function, or an oscilloscope. The leads would be connected to the signal wire and ground.
Warning: Do NOT use an ordinary voltmeter to check a Ford BP/MAP sensor because doing so can damage the electronics inside the sensor. This type of sensor can only be diagnosed with a DVOM that displays frequency, or a scope or scan tool.
Another way to check out a Ford digital MAP sensor circuit is to input a "simulated" MAP sensor signal with a tester that can generate an adjustable frequency signal. Changing the frequency of the simulated signal should trick the computer into changing the fuel mixture (look for a change in the injector pulse width signal).
No change would indicate a possible computer problem.
MAP SENSOR REPLACEMENT
If a MAP sensor needs to be replaced, make sure the replacement is the correct one for the application. Differences in calibration between model years and engines will affect the operation of the engine management system.
If a vehicle is more than five years old, the vacuum hose that connects the MAP sensor to the engine should also be replaced.
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P0069 Manifold Absolute Pressure – Barometric Pressure Correlation (Dodge/Ram)
To find the right fix, begin your diagnosis at the air intake. Open the air box and look for blockages. A dirty air filter can trigger this code, but so could a blockage further into the intake (so be sure to trace airflow from the airbox all the way to the intake manifold). Many times, simply replacing the filter and clearing the code will resolve a P0069 in your Dodge.
However, if no problems are found and a new air filter does not do the job, then the problem is very likely in the IAT (intake air temperature) sensor.
The IAT sensor is located on the intake, and it records the temperature of the air coming into the intake manifold. If this sensor becomes faulty, it can trigger a MAP BPC and a P0069 trouble code. Replacing the IAT sensor is a relatively simple and straight-forward job, and fortunately the parts are not expensive.
NOTE: P0069 and other codes can also be triggered when an after-market chipset has been installed on a Cummins engine computer. This can cause a short or default in the system, setting off codes like P0069. If your Dodge has after-market chips installed, and if your air filter seems clean, you might try diagnosing this code by first uninstalling the non-OEM chips and resetting the system.
If you find your after-market chip is the cause of the problem, it might make sense to remove it permanently. While some after-market programmers and tools can add real power to your diesel, cheap products that promise big horsepower gains for less than $100 should probably be avoided.
After all, if the after-market could figure out a way to boost horsepower by adding a really cheap computer chip to your diesel, don't you think Dodge or Ram would be putting these chips on at the factory?
IN other words, if it seems too good to be true, it probably is.
Author Jason Lancaster is the editor of ExhaustVideos.com, a website that helps vehicle owners find the best after-market exhaust system. Jason also works with WeRMopar.com, a website that offers discounted OEM Dodge Parts online – click herefor more info.
DTC P0069: Abnormal Correlation Between Manifold Absolute Pressure Sensor And Barometric Pressure Sensor
TECHNICAL DESCRIPTION
The ECM detects abnormality in the sensor by comparing the manifold absolute pressure sensor output with the barometric pressure sensor output.
DESCRIPTIONS OF MONITOR METHODS
The ECM compares the manifold absolute pressure sensor output with the barometric pressure sensor output while the engine control relay is in "ON" position after the ignition switch is in "LOCK" (OFF) position. When the difference exceeds the specified value between them, the ECM determines whether the manifold absolute pressure sensor / the barometric pressure sensor has malfunction or not.
Check Conditions
Ignition switch is in "LOCK" (OFF) position.
After 2 seconds pass from the time when the engine is stopped.
Engine coolant temperature is higher than 0 °C (32 °F) .
Judgement Criterion
Difference between manifold absolute pressure sensor output and barometric pressure sensor output is more than 9 kPa (2.7 in.Hg) for 2 seconds .
OBD-II DRIVE CYCLE PATTERN
None.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
Manifold absolute pressure sensor failed.
Barometric pressure sensor failed.
ECM failed.
P0108 - MAP Pressure Circuit High Input OBD-II Trouble Code Technical Description Manifold Absolute Pressure/Barometric Pressure Circuit High Input 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 exhaust Causes 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 vacuum Possible 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.
Read more at: http://www.obd-codes.com/p0108
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