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

P0102-MASS AIR FLOW SENSOR CIRCUIT LOW

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


Theory of Operation

The Intake Air Temperature (IAT) Sensor is combined with the Mass Air Flow Sensor. It is located on the Air Cleaner Box and is used to monitor the temperature of the air entering the intake system. The Intake Air Temperature Sensor operates as a typical two wire sensor. It receives a 5-Volt signal on the (K362) Intake Air Temperature Sensor Signal circuit and uses the (K916) Sensor Ground circuit. When this fault code is active the EGR system will be disabled.



Possible Causes

INTAKE/EXHAUST SYSTEM PROBLEMS
(F888) MASS AIR FLOW SENSOR 5-VOLT SUPPLY CIRCUIT OPEN/HIGH RESISTANCE
(K157) MASS AIR FLOW SENSOR SIGNAL CIRCUIT OPEN/HIGH RESISTANCE
(K157) MASS AIR FLOW SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
(K157) MASS AIR FLOW SENSOR SIGNAL CIRCUIT SHORTED TO THE (K957) MASS AIR FLOW SENSOR GROUND CIRCUIT
MASS AIR FLOW 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



NOTE: If any Sensor Reference DTCs are present, perform the applicable diagnostic procedure before continuing with this test.
1. Ignition on, engine not running.
2. With the scan tool, clear DTCs in the Powertrain Control Module (PCM).
3. Start the engine and allow it to reach normal operating temperature.
4. With the scan tool, select View DTCs.


Is the status Active for this DTC?

Yes


No


2. CHECK FOR INTAKE AND EXHAUST SYSTEM RESTRICTIONS

1. Turn the ignition off.
2. Inspect the exhaust system for damaged components that could cause exhaust flow blockage.
3. Inspect all air intake, crankcase vent and turbocharger related hoses/tubes and connections for damage, air leaks or blockage.
4. Inspect the Charge Air Cooler hoses/tubes and connections for damage, air leaks or blockage.
5. Inspect the air filter for excessive dirt, soiling or other problems that may cause restricted air flow.


Were any problems found?

Yes


No


3. CHECK THE (K157) MASS AIR FLOW SENSOR SIGNAL CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Turn the ignition off.
2. Disconnect the Mass Air Flow Sensor harness connector.
3. Disconnect the PCM C1 harness connector.
4. Measure the resistance of the (K157) Mass Air Flow Sensor Signal circuit between the Mass Air Flow Sensor connector and the PCM C1 harness connector.


Is the resistance below 5.0 Ohms?

Yes


No


4. CHECK THE (F888) MASS AIR FLOW SENSOR 5-VOLT SUPPLY CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Measure the resistance of the (F888) Mass Air Flow Sensor 5-Volt Supply circuit between the Mass Air Flow Sensor harness connector and the PCM C1 harness connector.


Is the resistance below 5.0 Ohms?

Yes


No


5. CHECK THE (K157) MASS AIR FLOW SENSOR SIGNAL CIRCUIT FOR A SHORT TO GROUND
1. Measure the resistance between ground and the (K157) Mass Air Flow Sensor Signal circuit in the Mass Air Flow Sensor harness connector.


Is the resistance above 10k Ohms?

Yes


No


6. CHECK FOR HE (K157) MASS AIR FLOW SENSOR SIGNAL CIRCUIT SHORTED TO THE (K957) MASS AIR FLOW SENSOR GROUND CIRCUIT
1. Measure the resistance between the (K157) Mass Air Flow Sensor Signal circuit and the (K957) Mass Air Flow Sensor Ground circuit in the Mass Air Flow Sensor harness connector.


Is the resistance above 10k Ohms?

Yes


No


7. MASS AIR FLOW SENSOR

1. Reconnect the PCM C1 harness connector.
2. Replace the Mass Air Flow Sensor in accordance with the service information.
3. Turn the ignition on.
4. With the scan tool, clear DTCs.
5. Start the engine and allow it to reach normal operating temperature.
6. With the scan tool, select View DTCs.


Is the status Active for this DTC?

Yes


No


8. POWERTRAIN CONTROL MODULE

1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Mass Air Flow 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 any Technical Service Bulletins that may apply.


Were any problems found?

Yes


No