3.1. What circuit to check for MAP sensor to computer?

Basically, the vehicle's computer is not detecting the required pressure change in the manifold.

Possible causes
Faulty Manifold Absolute Pressure (MAP) Sensor
Restricted MAP Sensor
MAP Sensor harness is open or shorted
MAP Sensor circuit poor electrical connection
Faulty Engine Control Module (ECM)

I'm not sure I understand your question. When I first read it I thought you were saying you had an error code that the engine idle is low, but the error code you've given is for a MAP sensor problem which you mentioned in your post also. I'm going to guess that you've observed the low idle yourself, and when you ran the diagnostics the engine computer was complaining of a bad MAP sensor signal. This is triggered when the engine computer sees a change in another sensor that should correlate with a certain change in the MAP sensor, but the MAP sensor signal doesn't change as expected. Idle problems are a possible symptom of a bad MAP sensor, so this is not unreasonable. What your engine is telling you is that you should check the MAP sensor and its related wiring and hose connections to try to find your problem. If you fix the problem with the MAP sensor then your idle may start working properly again.

Hi there,

If you are correct with your code reader, this condition should trigger fault code: P0107.

This relates to your MAP/BARO Sensor's signal voltage is too low (below 0.25v).

This condition will cause all sorts of engine running issues....

First, using your scan tool with the Key on and engine running, monitor the MAP Sensor voltage. If it is reading less than 5 volts, turn engine off, unplug the MAP sensor and, using a DVOM (Digital Volt/Ohm Meter) check for 5Volts on the 5 Volt reference circuit.

1. If there is not 5 Volts on the reference circuit, then check for the reference voltage at the PCM connector. If it is present at the PCM connector but not the MAP connector, repair the open in the wiring loom between the PCM and MAP harness connector.

If 5 Volt reference is NOT present at the PCM connector, check powers and grounds of PCM and repair/replace as needed.

2. If you have a 5 Volt reference at the MAP connector, jumper the 5 volt reference circuit to the signal circuit. Now check the MAP voltage on the scan tool. It should be 4.5 to 5 Volts. If it is, replace MAP sensor. If not, repair open/short in the signal circuit wiring and re-check.

3. If all appears okay, perform a wiggle test. Start engine and manipulate the harness, connector and tap on the MAP sensor. Note any changes in voltage or engine speed. Repair connector, harness, or sensor as needed.

4. If the wiggle test checks out, use a vacuum pump (or just use your lungs) to draw a vacuum on the MAP sensor vacuum port. As you add vacuum the voltage should decrease. With no vacuum, the MAP sensor should read approximately 4.5 volts. If there is no change in MAP sensor reading on the scan tool, replace MAP sensor.

Cheers,

you will need to some testing to islate problem

Turn ON the ignition, with the engine OFF.
Disconnect the MAP sensor.
Connect a voltmeter between the MAP sensor 5-volt reference circuit and a good ground.
Measure for a proper range of 4.8-5.2 volts between the MAP sensor 5-volt reference circuit and a good ground.
If the voltage is less than the specified range, then test the circuit for a high resistance. If the is normal, replace the ECM. If the voltage is more than the specified range, then test the circuit for a short to voltage. If the circuit is normal, replace the ECM.With the MAP sensor still disconnected, use the scan tool to observe the MAP Sensor parameter for the proper value of less than 12 kPa.
If the MAP Sensor parameter is more than 12 kPa, then test the MAP sensor signal circuit for a short to voltage. If the circuit is normal, replace the ECM.Connect a jumper wire between the MAP sensor 5-volt reference circuit and the MAP sensor signal circuit.
Use the scan tool to observe the MAP Sensor parameter for the proper value of more than 103 kPa.
If the MAP Sensor parameter is less than 103 kPa, then test the MAP sensor signal circuit for a high resistance. If the circuit is normal, replace the ECM.Turn OFF the ignition, and all electrical accessories. Allow sufficient time for the control module to power down before taking a resistance measurement.
Measure for a proper value of less than 5 ohms of resistance between the low reference circuit of the MAP sensor and a good ground.
If the resistance is more than 5 ohms, then test the circuit for a high resistance. If the circuit tests normal, replace the ECM.If the MAP sensor circuits test normal, then replace the MAP sensor.

Is there a good vacuum supply to the MAP

P0107 - Manifold Absolute Pressure/Barometric Pressure Circuit Low Input

The Manifold Absolute Pressure (MAP) sensor responds to changes in the intake manifold pressure (vacuum). 5 Volts is supplied to the sensor from the PCM (powertrain control module). Inside the MAP sensor is a resistor that moves in relation to manifold pressure. The resistor varies the voltage between about 1 volt to 4.5 volts (depending on engine load) and that voltage signal is returned to the PCM to indicate manifold pressure (vacuum). This signal is essential for the PCM to determine fuel delivery. A P0107 DTC is set when the PCM sees that the MAP signal voltage is less than .25 volts which is too low.

Potential Symptoms: Anytime the MAP sensor signal is low the vehicle will likely have a very difficult time starting. Other symptoms may include:
* Hard to start
* Long cranking times
* Sputtering/missing
* Blowing black smoke
* Poor fuel economy
* Dies intermittently
* MIL(Malfunction Indicator Lamp) illumination

Causes: The causes of a low MAP sensor signal circuit (P0107) could be any of the following:
* Bad MAP sensor
* Open or short in the signal circuit
* Open or short in the 5 Volt reference circuit
* Ground circuit open or shorted
* Bad PCM

Possible Solutions: First, using a scan tool with the Key on and engine running, monitor the MAP sensor voltage. If it is reading less than .5 volts, turn engine off, unplug the MAP sensor and, using a DVOM (Digital Volt/Ohm Meter) check for 5Volts on the 5 Volt reference circuit.

1. If there is not 5 Volts on the reference circuit, then check for the reference voltage at the PCM connector. If it is present at the PCM connector but not the MAP connector, repair the open in the reference circuit between the PCM and MAP harness connector. If 5 Volt reference is NOT present at the PCM connector, check powers and grounds of PCM and repair/replace as needed. (NOTE: On Chrysler products, a shorted Crank sensor, Vehicle speed sensor or any other sensor that utilizes the 5 Volt reference from the PCM can short out the 5 Volt reference. To fix simply unplug each sensor one at a time until the 5 Volt reference reappears. The last sensor unplugged is the shorted sensor.)

2. If you have a 5 Volt reference at the MAP connector, jumper the 5 volt reference circuit to the signal circuit. Now check the MAP voltage on the scan tool. It should be 4.5 to 5 Volts. If it is, replace MAP sensor. If not, repair open/short in the signal circuit wiring and re-check.

3. If all appears okay, perform a wiggle test. Start engine and manipulate the harness, connector and tap on the MAP sensor. Note any changes in voltage or engine speed. Repair connector, harness, or sensor as needed.

4. If the wiggle test checks out, use a vacuum pump (or just use your lungs) to draw a vacuum on the MAP sensor vacuum port. As you add vacuum the voltage should decrease. With no vacuum, the MAP sensor should read approximately 4.5 volts. If there is no change in MAP sensor reading on the scan tool, replace MAP sensor.

MAP Sensor DTC's: P0105, P0106, P0107, P0108 and P0109.

Hope helps (remember rated and comment this).

The Manifold Absolute Pressure (MAP) sensor responds to changes in the intake manifold pressure (vacuum). 5 Volts is supplied to the sensor from the PCM (powertrain control module). Inside the MAP sensor is a resistor that moves in relation to manifold pressure. The resistor varies the voltage between about 1 volt to 4.5 volts (depending on engine load) and that voltage signal is returned to the PCM to indicate manifold pressure (vacuum). This signal is essential for the PCM to determine fuel delivery. A P0107 DTC is set when the PCM sees that the MAP signal voltage is less than .25 volts which is too low.

Potential Symptoms Anytime the MAP sensor signal is low the vehicle will likely have a very difficult time starting. Other symptoms may include:

• Hard to start
• Long cranking times
• Sputtering/missing
• Blowing black smoke
• Poor fuel economy
• Dies intermittently
• MIL(Malfunction Indicator Lamp) illumination

Causes The causes of a low MAP sensor signal circuit (P0107) could be any of the following:

• Bad MAP sensor
• Open or short in the signal circuit
• Open or short in the 5 Volt reference circuit
• Ground circuit open or shorted
• Bad PCM

Possible Solutions First, using a scan tool with the Key on and engine running, monitor the MAP sensor voltage. If it is reading less than .5 volts, turn engine off, unplug the MAP sensor and, using a DVOM (Digital Volt/Ohm Meter) check for 5Volts on the 5 Volt reference circuit.
1. If there is not 5 Volts on the reference circuit, then check for the reference voltage at the PCM connector. If it is present at the PCM connector but not the MAP connector, repair the open in the reference circuit between the PCM and MAP harness connector. If 5 Volt reference is NOT present at the PCM connector, check powers and grounds of PCM and repair/replace as needed. (NOTE: On Chrysler products, a shorted Crank sensor, Vehicle speed sensor or any other sensor that utilizes the 5 Volt reference from the PCM can short out the 5 Volt reference. To fix simply unplug each sensor one at a time until the 5 Volt reference reappears. The last sensor unplugged is the shorted sensor.)
2. If you have a 5 Volt reference at the MAP connector, jumper the 5 volt reference circuit to the signal circuit. Now check the MAP voltage on the scan tool. It should be 4.5 to 5 Volts. If it is, replace MAP sensor. If not, repair open/short in the signal circuit wiring and re-check.
3. If all appears okay, perform a wiggle test. Start engine and manipulate the harness, connector and tap on the MAP sensor. Note any changes in voltage or engine speed. Repair connector, harness, or sensor as needed.
4. If the wiggle test checks out, use a vacuum pump
(or just use your lungs) to draw a vacuum on the MAP sensor vacuum port. As you add vacuum the voltage should decrease. With no vacuum, the MAP sensor should read approximately 4.5 volts. If there is no change in MAP sensor reading on the scan tool, replace MAP sensor.

Computers and Control Systems: Diagnostic Trouble Code Tests and Associated Procedures
P0236
SYMPTOM
P0236-MAP SENSOR TOO HIGH TOO LONG
WHEN MONITORED
Engine running.
SET CONDITION
Boost pressure signal indicates boost pressure is high when other engine parameters (i.e. speed and load) indicate boost pressure should be low or
boost pressure is low when other engine parameters indicate it should be high.
POSSIBLE CAUSES
- Other codes
- Checking boost pressure sensor
- Checking the 5-volt supply circuit
- Sensor ground circuit open
- MAP sensor
- MAP signal circuit open
- MAP signal circuit STV
- MAP signal circuit STSG
- MAP signal circuit STG
- ECM

A MAP sensor problem will cause the symptoms you are experiencing. The MAP sensor is critical because you have a speed density type fuel injection system. Without the MAP sensor signal or an inaccurate one, the ECM won't know the engine load for ignition timing and fuel injection adjustments. The engine computer is detecting a high voltage condition on the MAP sensor signal circuit.
Inspect the vacuum hose going to the MAP sensor. Replace it if is looks cracked or if it collapses on itself. Make sure that the MAP sensor has vacuum by disconnecting the hose from the sensor when the engine is running and feeling for vacuum.

If you have vacuum, you can check the MAP sensor and its circuits with a multimeter. There are three wires going to the sensor. I am not sure on the colors, but Yellow should have 5 V on it with the key on. Brown is ground and should read close to 0 ohms. Light Green with a Red stripe should have 5V on it with the key on. If you backprobe the MAP sensor connector with it plugged into the MAP sensor on the light green/red wire and apply vacuum to the sensor, the voltage should drop.