2014 Jeep Wrangler JK Factory Service Manual 28 - DTC-Based Diagnostics

P0108-MANIFOLD ABSOLUTE PRESSURE SENSOR CIRCUIT HIGH

For a complete wiring diagram, refer to the Wiring Information.


Theory of operation

The Manifold Absolute Pressure (MAP) sensor is a transducer that varies resistance according to changes in altitude and atmospheric conditions. The MAP reading gives the Powertrain Control Module (PCM) an indication of the current air pressure within the intake manifold. The PCM uses this information to calculate fuel delivery. The MAP sensor has a 5 Volt reference circuit, a low reference circuit and a signal circuit. The PCM supplies 5 Volts to the MAP sensor on a 5 Volt reference circuit and provides a ground on a low reference circuit. The MAP sensor provides a voltage signal to the PCM on a signal circuit relative to the pressure changes.


Possible Causes

(F856) 5-VOLT SUPPLY CIRCUIT SHORTED TO VOLTAGE
(K1) MAP SIGNAL CIRCUIT SHORTED TO VOLTAGE
(K1) MAP SIGNAL CIRCUIT SHORTED TO THE (F856) 5-VOLT SUPPLY CIRCUIT
(K1) MAP SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE
(K900) SENSOR GROUND CIRCUIT OPEN OR HIGH RESISTANCE
MAP SENSOR
POWERTRAIN CONTROL MODULE (PCM)

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).


1. DTC IS ACTIVE

1. Start the engine and allow it to reach normal operating temperature.

WARNING:

When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

2. With the scan tool, select View DTCs.


Is the status Active for this DTC?

Yes


No


2. (F856) 5-VOLT SUPPLY CIRCUIT SHORTED TO VOLTAGE
1. Turn the ignition off.
2. Disconnect the Manifold Absolute Pressure (MAP) Sensor harness connector.
3. Disconnect the PCM C2 harness connector.
4. Turn the ignition on.
5. Measure the voltage of the (F856) 5 Volt Supply circuit in the Manifold Absolute Pressure Sensor harness connector.


Is there any voltage present?

Yes


No


3. (K1) MAP SIGNAL CIRCUIT SHORTED TO VOLTAGE
1. Measure the voltage of the (K1) MAP Signal circuit in the MAP Sensor harness connector.


Is there any voltage present?

Yes


No


4. (K1) MAP SIGNAL CIRCUIT SHORTED TO THE (F856) 5-VOLT SUPPLY CIRCUIT
1. Measure the resistance between the (K1) MAP Signal circuit and the (F856) 5-Volt Supply in the MAP Sensor harness connector.


Is the resistance below 100 Ohms?

Yes


No


5. (K1) MAP SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE

1. Turn the ignition off.
2. Measure the resistance of the (K1) MAP Signal between the MAP Sensor harness connector and the PCM C2 harness connector.


Is the resistance below 5.0 Ohms?

Yes


No


6. (K900) SENSOR GROUND CIRCUIT OPEN OR HIGH RESISTANCE
1. Measure the resistance of the (K900) Sensor Ground circuit between the MAP Sensor harness connector and the PCM C2 harness connector.


Is the resistance below 5.0 Ohms?

Yes


No


7. MAP SENSOR
1. Turn the ignition off.
2. Connect the PCM C2 harness connector.
3. Connect a jumper wire between the (K900) Sensor Ground circuit and the (K1) MAP Signal circuit in the MAP Sensor harness connector.
4. Turn the ignition on.
5. With the scan tool, read the MAP Sensor signal voltage.


Is the voltage below 1.0 volt with the jumper wire in place?

Yes


No


8. POWERTRAIN CONTROL MODULE (PCM)

1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Manifold Absolute Pressure Sensor and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals.
4. Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.
5. Look for the data to change or for the DTC to reset during the wiggle test.
6. Perform the Technical Service Bulletins that may apply.


Were any problems found?

Yes


No