MAP sensor output voltage too low?

Here is an explanation from the manual for the 4.3L spark control:

Description & Operation The HEI (EST) distributor uses a modified ignition module. The module has seven or eight terminals instead of the four used without EST. Different terminal arrangements are used, depending upon engine application.
To properly control ignition/combustion timing, the ECM needs to know the following information:

• Crankshaft position
• Engine speed (rpm)
• Engine load (manifold pressure or vacuum)
• Atmospheric (barometric) pressure
• Engine temperature
• Transmission gear position (certain models)

The ECM uses information from the MAP and coolant sensors in addition to rpm to calculate spark advance as follows:

• Low MAP output voltage would require MORE spark advance.
• Cold engine would require MORE spark advance.
• High MAP output voltage would require LESS spark advance.
• Hot engine would require LESS spark advance.

Incorrect operation of the EST system can cause the following:

• Detonation-low MAP output or high resistance in the coolant sensor circuit.
• Poor performance-high MAP output or low resistance in the coolant sensor circuit.

The EST system consists of the distributor module, ECM and its connecting wires.
Copyright ©2020 by Chilton, an imprint of Cengage Learning

Code 54 is fuel pump circuit, Low voltage,will cause car not to start. Wiring open circuit/short circuit to ground, fuel pump relay, engine oil pressure warning lamp switch
Code 33 is MAP sensor,voltage high, low vacuum indicated.
Wiring short circuit to positive, hose blocked/leaking, MAP sensor, ECM
Check the attached links,
"I hope this helped you out, if so let me know by pressing the helpful button. Check out some of my other posts if you need more tips and info."
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wow , you actually tried to look it up, a 1st time here.

the MAP is a baro sensor used to calculate fuel injection RATES.

if you have gross air leaks to the system the engine IDLE screams.

is it?

108 means the voltage is too high.

usually its unplugged, or bad sensor.

otential 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



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



http://www.obd-codes.com/p0108



and last. but before ECU.

low engine compression, is 1 more, causes , many



what i do is reseat the MAP sensor

i then make sure he vacuum port is not clogged. (both sides)

i then measure the output , keyon, and idle and gunning throttle.

any Voltmeter works here,

key on is 5v or near.

idle 1.8v

gun engine as the RPMs fall like a rock the volts tries to hit 0.5vdc.



http://www.fixkick.com/look/odds-ends/jeep/MAP-sensor-output-real.jpg



very very easy to find with a voltmeter

if the meter agrees with vacuum gage, then the MAP is ok

and you have air leaks or low vacuum for (VAST reasons)

ask.

Chrysler codes,. only.

p0106,

on newer Chysler, cars they have many codes with 106, leaving out the prefix is bad idea.

Like U0102

or C0106?

P0106 is MAP performance failure. (that dont mean replace it)

the puter has no IDEA what is wrong, only that tests failed.

here are the conditions.

When Monitored and Set Condition

• When Monitored: Engine running for at least 30 seconds and no fault in the throttle valve actuator.



• Set Condition: Low limit: The Manifold Absolute Pressure (MAP) Sensor reading is below a calculated value when the throttle valve angle is greater than 80F for approximately 5 seconds. High limit: The MAP Sensor reading is greater than a calculated value that is determined by engine speed and throttle valve angle for approximately 5 seconds.

now in gringo or bar stool.

1: the puter brain saw you go near wide open throttle and the

map sensor (vacuum sensor) do not show new zero vacuum.

even a clogged air filter could do this, causing a false high vacuum







POSSIBLE CAUSES




MANIFOLD ABSOLUTE PRESSURE SENSOR SIGNAL CIRCUIT OPEN




MANIFOLD ABSOLUTE PRESSURE SENSOR SIGNAL CIRCUIT SHORT TO GROUND




MANIFOLD ABSOLUTE PRESSURE SENSOR SIGNAL CIRCUIT SHORT TO VOLTAGE




5-VOLT SUPPLY CIRCUIT OPEN




5-VOLT SUPPLY CIRCUIT SHORT TO GROUND




5-VOLT SUPPLY CIRCUIT SHORT TO VOLTAGE




5-VOLT SUPPLY CIRCUIT SHORT TO SENSOR GROUND CIRCUIT




MANIFOLD ABSOLUTE PRESSURE SENSOR SIGNAL CIRCUIT SHORT TO SENSOR GROUND CIRCUIT




MANIFOLD ABSOLUTE PRESSURE SENSOR SIGNAL CIRCUIT SHORT TO 5-VOLT SUPPLY CIRCUIT




SENSOR GROUND CIRCUIT OPEN




ENGINE OIL SENSOR




MANIFOLD ABSOLUTE PRESSURE SENSOR




POWERTRAIN CONTROL MODULE






then the FSM goes to step by step tests. to find above reasons.

omitted. (too long )



the word low is ambiguous in all FSM.

it can mean, low plenum pressure,

or low vacuum (opposite)

and low voltage, its a pain in the xxx to find this fact out.

the map outputs high voltage for low vacuum (same as high absolute pressure)



the fsm tests are inane.

we check the voltage out of the map

at keyon

running

and wide open throttle for 1 second. just gun it and watch.

here is what it does.

left side is wide open throttle, idle is 20 inchs. key on is, WOT.

so, what is that

4.5v is keyon

start engine, get about 1.5v

the gun engine, then drop throttel to zero throttle fast

the causes,. huge vacuum about 24 inches, or 1v or less

this is a working MAP. if those tests pass.

the test (OBD2 monitor) fails for about not getting near 4vdc from MAP output pin, DOES THIS HELP?

Manifold Absolute Pressure Sensor

• OPERATION
• TESTING
• REMOVAL & INSTALLATION

Print

OPERATION

See Figures 1, 2 and 3

Fig. Fig. 1: MAP sensor location-2.4L engine

Fig. Fig. 2: MAP sensor location-3.0L engine

Fig. Fig. 3: MAP sensor location-3.3L and 3.8L engines
The PCM supplies 5 volts of direct current to the Manifold Absolute Pressure (MAP) sensor. The MAP sensor then converts the intake manifold pressure into voltage. The PCM monitors the MAP sensor output voltage. As vacuum increases, the MAP sensor voltage decreases proportionately. Also, as vacuum decreases, the MAP sensor voltage increases proportionally.
With the ignition key ON , before the engine is started, the PCM determines atmospheric air pressure from the MAP sensor voltage. While the engine operates, the PCM figures out intake manifold pressure from the MAP sensor voltage. Based on the MAP sensor voltage and inputs from other sensors, the PCM adjusts spark advance and the air/fuel ratio. The MAP sensor is mounted to the intake manifold, near the throttle body inlet to the manifold. The sensor connects electrically to the PCM.

TESTING

See Figures 4, 5, 6 and 7

Fig. Fig. 4: Disengage the MAP sensor connector-3.0L engine shown

WARNING When testing the MAP sensor, make sure the harness wires do not become damaged by the test meter probes.

1. Visually check the connector, making sure it is attached properly and that all of the terminals are straight, tight and free of corrosion.

Fig. Fig. 5: MAP sensor connector terminal identifications: (A) 5-volt supply, (B) sensor signal, (C) ground-3.0L engine shown

Fig. Fig. 6: MAP sensor connector terminal identifications-2.4L, 3.3L and 3.8L engines

Fig. Fig. 7: Using a digital volt-ohmmeter, test the MAP sensor voltage-3.0L engine shown

1. Test the MAP sensor output voltage at the sensor connector between terminals B and C (2.4L, 3.3L and 3.8L engines), or A nd B (3.0L engine).
2. With the ignition switch ON and the engine not running, the output voltage should be 4-5 volts. The voltage should fall to 1.5-2.1 volts with a hot, neutral idle speed condition. If OK, go to the next step. If not OK, go to Step 5.
3. Test the PCM terminal 36 for the same voltage described in the previous step to make sure the wire harness is OK. Repair as necessary.
4. Test the MAP sensor ground circuit at the sensor connector terminal A (2.4L, 3.3L and 3.8L engines) or C (3.0L engine) and PCM terminal 43. If OK, go to the next step. If not OK, repair as necessary.
5. Test the MAP sensor supply voltage between the sensor connector terminals A and B (2.4L, 3.3L and 3.8L engines) r A and C (3.0L engine) with the ignition key in the ON position. The voltage should be about 4.5-5.5 volts.
6. There should also be 4.5-5.5 volts at terminal 61 of the PCM. If OK, replace the MAP sensor.
7. If not, repair or replace the wire harness as required.

REMOVAL & INSTALLATION

See Figures 1, 2, 3 and 4
The MAP sensor is mounted on the intake manifold near the throttle body inlet to the manifold.

1. Disconnect the negative battery cable.
2. On the 3.0L engine only, disconnect the vacuum hose from the MAP sensor.
3. Detach the electrical connector from the MAP sensor.
4. Unfasten the mounting screws, then remove the MAP sensor from the vehicle.

To install:

1. Install the sensor onto the intake manifold and tighten the mounting screws to 35 inch lbs. (4 Nm).
2. Attach the sensor electrical connector.
3. On the 3.0L engine, connect the vacuum hose to the MAP sensor.
4. Connect the negative battery cable.

Hi, please use a voltmeter set to VDC to check the inputs and outputs of the MAP sensor as indicated below. Please get back to me with questions or results of your test.

Testing

1. Visually check the connector, making sure it is attached properly and that all of the terminals are straight, tight and free of corrosion. Reinstall the connector and probe the back of the connector where the wires go in to check the output as follows.
2. Test the MAP sensor output voltage at the sensor connector between terminals B and C (2.4L, 3.3L and 3.8L engines), or A and B (3.0L engine).
3. With the ignition switch ON and the engine not running, the output voltage should be 4-5 volts. The voltage should fall to 1.5-2.1 volts with a hot, neutral idle speed condition. If OK, go to the next step. If not OK, go to Step 5.
4. Test the PCM terminal 36 for the same voltage described in the previous step to make sure the wire harness is OK. Repair as necessary.
5. Test the MAP sensor ground circuit at the sensor connector terminal A (2.4L, 3.3L and 3.8L engines) or C (3.0L engine) and PCM terminal 43. If OK, go to the next step. If not OK, repair as necessary.
6. Test the MAP sensor supply voltage between the sensor connector terminals A and B (2.4L, 3.3L and 3.8L engines), or A and C (3.0L engine) with the ignition key in the ON position. The voltage should be about 4.5-5.5 volts.
7. There should also be 4.5-5.5 volts at terminal 61 of the PCM. If OK, replace the MAP sensor.
8. If not, repair or replace the wire harness as required.

Trouble Code: P1297

No Change In MAP Signal From Start To Run Transition
Possible Causes:


Engine vacuum port to MAP Sensor clogged, dirty or restricted MAP Sensor signal is skewed or the Sensor is out-of-calibration MAP Sensor VREF circuit open or grounded (intermittent fault) PCM has failed

Hi,
OBD II Fault Code

• OBD II P0108

Fault Code Definition
The Manifold Absolute Pressure Sensor/Barometric Pressure Sensor measures the rise and fall of the air pressure inside the Intake Manifold. This provides critical data needed for the Power Train Control Module (PCM) to control the Air Fuel Ratio, the Ignition Spark Timing, and many components of the Emissions Control Systems. The Manifold Absolute Pressure/Barometric Pressure Sensor converts the Intake Manifold air pressure into a voltage that is high when the Intake Manifold air pressure is high and low when the Intake Manifold air pressure drops to a vacuum. The P0108 code indicates a high voltage input from the Manifold Absolute Pressure Sensor/Barometric Pressure Sensor to the Power Train Control Module.
Symptoms

• Check Engine Light will illuminate
• In many cases, no abnormal symptoms may be noticed
• In some cases, the engine may be hard starting and/or get poor fuel economy
• In some cases, noticeably poor engine performance may occur

Common Problems That Trigger the P0108 Code

• Manifold Absolute Pressure Sensor/Barometric Pressure Sensor is defective
  
• Intake Manifold vacuum leaks
• Faulty or corroded Manifold Absolute Pressure Sensor/Barometric Pressure wiring or connections

Common Misdiagnoses

• Manifold Absolute Pressure Sensor/Barometric Pressure Sensor is replaced when the real cause is an Intake Manifold vacuum leak
  
• Manifold Absolute Pressure Sensor/Barometric Pressure Sensor is replaced when the real cause is a stuck-open EGR Valve
• Manifold Absolute Pressure Sensor/Barometric Pressure Sensor is replaced when the real problem is a defective Idle Air Control Motor, which causes a very low engine idle

To retrieve OBDII Error codes from your Chrysler/Jeep/Dodge vehicle, do the following sequence with the key: ON-ACC-ON-ACC-ON and look at the odometer, that is where codes will be displayed. Here are the codes that you may/can get.

Ho2S = heated oxyen sensor, TP = throttle position, MAF = mass airflow, MAP = manifold absolute pressure, TC=turbocharger.P0030 HO2S Heater Control Circuit Bank 1 Sensor 1
P0031 HO2S Heater Circuit Low Voltage Bank 1 Sensor 1
P0032 HO2S Heater Circuit High Voltage Bank 1 Sensor 1
P0036 HO2S Heater Control Circuit Bank 1 Sensor 2
P0037 HO2S Heater Circuit Low Voltage Bank 1 Sensor 2
P0038 HO2S Heater Circuit High Voltage Bank 1 Sensor 2
P0050 HO2S Heater Circuit Bank 2 Sensor 1
P0051 HO2S Heater Circuit Low Voltage Bank 2 Sensor 1
P0052 HO2S Heater Circuit High Voltage Bank 2 Sensor 1
P0056 HO2S Heater Circuit Bank 2 Sensor 2
P0057 HO2S Heater Circuit Low Voltage Bank 2 Sensor 2
P0058 HO2S Heater Circuit High Voltage Bank 2 Sensor 2
P0100 MAF Sensor Ckt. Insufficient Activity
P0101 Mass Air Flow (MAF) Sensor Performance
P0102 Mass Air Flow (MAF) Sensor Circuit Low Frequency
P0103 Mass Air Flow (MAF) Sensor Circuit High Frequency
P0104 Mass Air Flow Circuit Intermittent
P0105 MAP Sensor Circuit Insufficient Activity
P0106 Manifold Absolute Pressure (MAP) System Performance
P0107 Manifold Absolute Pressure (MAP) Sensor Circuit Low Voltage
P0108 Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage
P0109 Manifold Absolute Pressure Circuit Intermittent
P0110 Intake Air Temperature (IAT) Sensor Circuit
P0111 Intake Air Temperature (IAT) Sensor Performance
P0112 Intake Air Temperature (IAT) Sensor Circuit Low Voltage
P0113 Intake Air Temperature (IAT) Sensor Circuit High Voltage
P0114 Intake Air Temperature Circuit Intermittent
P0115 Engine Coolant Temperature (ECT) Sensor Circuit
P0116 Engine Coolant Temperature (ECT) Sensor Performance
P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage
P0118 Engine Coolant Temperature (ECT) Sensor Circuit High Voltage
P0119 Engine Coolant Temperature Circuit Intermittent
P0120 Throttle Position System Performance
P0121 Throttle Position Sensor Circuit Insufficient Activity
P0122 Throttle Position (TP) Sensor Circuit Low Voltage
P0123 Throttle Position (TP) Sensor Circuit High Voltage
P0124 Throttle Position Sensor 1 Circuit Intermittent
P0125 Engine Coolant Temperature (ECT) Insufficient for Closed Loop Fuel Control
P0126 Insufficient Engine Coolant Temperature for Stable Operation
P0128 Coolant Thermostat
P0130 HO2S Circuit Closed Loop (CL) Performance Bank 1 Sensor 1
P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1
P0132 HO2S Circuit High Voltage Bank 1 Sensor 1
P0133 HO2S Slow Response Bank 1 Sensor 1
P0134 HO2S Circuit Insufficient Activity Bank 1 Sensor 1
P0135 HO2S Heater Performance Bank 1 Sensor 1
P0136 HO2S Circuit Bank 1 Sensor 2
P0137 HO2S Circuit Low Voltage Bank 1 Sensor 2
P0138 HO2S Circuit High Voltage Bank 1 Sensor 2
P0139 HO2S Slow Response Bank 1 Sensor 2
P0140 HO2S Circuit Insufficient Activity Bank 1 Sensor 2
P0141 HO2S Heater Performance Bank 1 Sensor 2
P0142 HO2S Circuit Bank 1 Sensor 3
P0143 HO2S Circuit Low Voltage Bank 1 Sensor 3
P0144 HO2S Circuit High Voltage Bank 1 Sensor 3
P0145 HO2S Circuit Bank 1 Sensor 2 Slow Response
P0146 HO2S Circuit Insufficient Activity Bank 1 Sensor 3
P0147 HO2S Heater Performance Bank 1 Sensor 3
P0150 HO2S Circuit Closed Loop (CL) Performance Bank 2 Sensor 1
P0150 HO2S Circuit Bank 2 Sensor 1
P0151 HO2S Circuit Low Voltage Bank 2 Sensor 1
P0152 HO2S Circuit High Voltage Bank 2 Sensor 1
P0153 HO2S Slow Response Bank 2 Sensor 1
P0154 HO2S Circuit Insufficient Activity Bank 2 Sensor 1
P0155 HO2S Heater Performance Bank 2 Sensor 1
P0156 HO2S Circuit Bank 2 Sensor 2
P0157 HO2S Circuit Low Voltage Bank 2 Sensor 2
P0158 HO2S Circuit High Voltage Bank 2 Sensor 2
P0159 HO2S Slow Response Bank 2 Sensor 2
P0160 HO2S Circuit Insufficient Activity Bank 2 Sensor 2
P0161 HO2S Heater Performance Bank 2 Sensor 2
P0162 HO2S Circuit Bank 2 Sensor 3
P0163 HO2S Circuit Bank 2 Sensor 3 Low Voltage
P0164 HO2S Circuit Bank 2 Sensor 3 High Voltage


P

recommend you check your MAP sensor. You will need a voltmeter.
If you don't have a vacuum gage, just use your mouth to pull a vacuum on the hose and see if the voltage drops when you do.
Let me know if you have questions.

OPERATION The Manifold Absolute Pressure (MAP) sensor, used on 1996-99 vehicles, measures the changes in intake manifold pressure which result from engine load/speed changes, and converts this information to a voltage output. The MAP sensor reading is the opposite of a vacuum gauge reading: when manifold pressure is high, MAP sensor value is high and vacuum is low. A MAP sensor will produce a low output on engine coast-down with a closed throttle while a wide open throttle will produce a high output. The high output is produced because the pressure inside the manifold is the same as outside the manifold, so 100 percent of the outside air pressure is measured.
The MAP sensor is also used to measure barometric pressure under certain conditions, which allows the PCM to automatically adjust for different altitudes.
The MAP sensor changes the 5 volt signal supplied by the PCM, which reads the change and uses the information to control fuel delivery and ignition timing.

TESTING See Figures 1 and 2

1. Visually check the connector, making sure it is properly connected and that all of its terminals are straight, tight and free of corrosion.
2. With the ignition ON , check the voltage between terminals A and B (probe the back of the connector to connect to these wires). It should be above 4 volts. Apply 15 in. Hg of vacuum at the MAP vacuum port and check the voltage again. The voltage should be 2 volts now.

Fig. Fig. 1: Manifold Absolute Pressure (MAP) sensor circuit
When pumping up and releasing the vacuum, check to make sure the voltage readings are smooth. When applying vacuum to the sensor, the change in voltage should happen instantly. A slow change in voltage could point to a faulty sensor.

Fig. Fig. 2: MAP sensor voltage specifications

1. If the sensor voltage is not within specification, check for a 5 volt reference at terminal C. If the reference signal is found, the sensor is faulty.
2. If the sensor and circuits are functional, the PCM may be faulty.

REMOVAL & INSTALLATION

3.8L (VIN K) Engine
See Figure 4
On these engines, the MAP sensor is mounted to the PCV valve cover.

1. Disconnect the negative battery cable.
2. Detach the MAP sensor electrical connector.
3. Carefully bend the locking tabs holding the MAP sensor to the PCV valve cover, just enough to remove the MAP sensor.
4. Pull the MAP sensor straight out of the PCV valve cover.

Fig. Fig. 4: On the 3.8L (VIN K) engine, the MAP sensor (1) is mounted in the PCV valve cover (2)

To install:

1. Make sure that the seal is installed on the MAP sensor and that it is not damaged.
2. Position and install the MAP sensor to the PCV valve cover. Make sure the locking tabs engage to hold the sensor to the cover.
3. Attach the sensor electrical connector.
4. Connect the negative battery cable.

It could just be a bad signal from the MAP sensor or a poor connection at the sensor. Or a bad MAP sensor itself. Maybe the vacuum line is off or broken.

Manifold Absolute Pressure (MAP) sensor measures the changes in the intake manifold pressure which result from engine load and speed changes, and converts this measurement into a voltage output.

A closed throttle on when the engine is decelerating would produce a relatively low MAP output, while a wide open throttle would produce a high output. Manifold absolute pressure is the opposite of what you would measure on a vacuum gage. When manifold pressure is high, vacuum is low. The MAP sensor is also used to measure barometric pressure under certain conditions, which allows the PCM to automatically adjust for different altitudes.

The PCM sends a 5 volt reference signal to the MAP sensor. As the manifold pressure changes, the electrical resistance of the sensor also changes. By monitoring the sensor output voltage, the PCM can determine the manifold pressure. A higher pressure, low vacuum (high voltage) requires more fuel, while a lower pressure, higher vacuum (low voltage) requires less fuel.

A high or low voltage fault in the MAP sensor circuit should set a DTC P0107 or DTC P0108. If the MAP sensor sends an intermittent zero voltage signal to the PCM, a DTC P0106 will set.