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

P034A-CRANKSHAFT POSITION SENSOR - CRANKSHAFT START POSITION INCORRECT

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


Theory of Operation

The Crankshaft Position (CKP) Sensor is a hall effect type sensor. The sensor produces a 5 Volt digital signal (square wave). The PCM provides a 5-Volt supply, 5-Volt Sensor Signal and ground to the CKP Sensor. The sensor is positioned opposite a magnetic ring at the rear of the crankshaft. The magnetic ring contains internal magnetic strips (electric teeth) that act on the hall-effect switch causing the digital switching of the sensor signal from high (5 Volts) to low (0 Volts).



Possible Causes

(K853) CKP SENSOR 5-VOLT SUPPLY CIRCUIT OPEN/HIGH RESISTANCE
(K24) CKP SENSOR SIGNAL CIRCUIT SHORTED TO VOLTAGE
(K925) CKP SENSOR GROUND CIRCUIT OPEN/HIGH RESISTANCE
(K24) CKP SENSOR SIGNAL CIRCUIT OPEN/HIGH RESISTANCE
(K853) CKP SENSOR 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
(K24) CKP SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
(K925) CKP SENSOR GROUND CIRCUIT OPEN/HIGH RESISTANCE
(K853) CKP SENSOR 5-VOLT SUPPLY CIRCUIT SHORTED TO THE (K925) CKP SENSOR GROUND CIRCUIT
(K24) CKP SENSOR SIGNAL CIRCUIT SHORTED TO THE (K925) CKP SENSOR GROUND CIRCUIT
CRANKSHAFT POSITION 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. VERIFY ACTIVE DTC



NOTE: If any Sensor Reference DTCs are present, perform the applicable diagnostic procedure before continuing with this test.

NOTE: The Timing Belt/Chain must be correctly installed and operational before diagnosis can be made. Refer to the service information to ensure the timing belt is properly installed.

NOTE: If the PCM detects and stores a DTC, the PCM also stores the engine/vehicle operating conditions under which the DTC was set. Some of these conditions are displayed on the scan tool at the same time the DTC is displayed.

NOTE: Before erasing stored DTCs, record these conditions. Attempting to duplicate these conditions may assist when checking for an active DTC.
1. Turn the ignition on.
2. With the scan tool, erase the PCM DTCs.
3. Attempt to start the engine cranking the engine for at least 7 seconds.
4. With the scan tool, read the PCM DTCs.


Does the scan tool display this DTC?

Yes


No


2. TEST DRIVE

1. Turn the ignition on.
2. With the scan tool, erase the PCM DTCs.
3. Test drive the vehicle.
4. With the scan tool, read the PCM DTCs.


Does the scan tool display this DTC?

Yes


No


3. CHECK THE (K24) CRANKSHAFT POSITION SENSOR SIGNAL CIRCUIT
1. Turn the ignition off.
2. Disconnect the Crankshaft Position Sensor harness connector.
3. Turn the ignition on.
4. Measure the voltage of the (K24) CKP Sensor Signal circuit at the CKP Sensor harness connector.


Select the appropriate voltage reading.

Voltage is above 5.2 Volts


Voltage is between 4.8 and 5.2 Volts


Voltage is below 4.8 Volts


4. CHECK THE (K24) CRANKSHAFT POSITION SENSOR SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE
1. Turn the ignition off.
2. Disconnect the PCM harness connectors.
3. Remove the ASD Relay.
4. Connect a jumper wire between cavity 30 and cavity 87 of the ASD Relay connector.
5. Turn the ignition on.
6. Measure the voltage of the (K24) CKP Sensor Signal circuit at the CKP Sensor harness connector.


Is the voltage below 1.0 Volt?

Yes


No


5. CHECK THE (K853) CRANKSHAFT POSITION SENSOR 5-VOLT SUPPLY CIRCUIT
1. Measure the voltage of the (K853) CKP Sensor 5-Volt Supply circuit at the CKP Sensor harness connector.


Select the appropriate voltage reading.

Voltage is above 5.2 Volts


Voltage is between 4.8 and 5.2 Volts


Voltage is below 4.8 Volts


6. CHECK THE (K925) CRANKSHAFT POSITION SENSOR GROUND CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Turn the ignition off.
2. Disconnect the PCM harness connectors.
3. Measure the resistance of the (K925) CKP Sensor Ground circuit between the CKP Sensor harness connector and the PCM harness connector.


Is the resistance below 5.0 Ohms?

Yes


No


7. DAMAGED CRANKSHAFT POSITION SENSOR OR CRANKSHAFT

1. Turn the ignition off.
2. Remove the CKP Sensor.
3. Inspect the CKP Sensor for conditions such as loose mounting screws, damage, or cracks.
4. Inspect the Crankshaft magnetic ring for conditions such as damage, or debris.


Is there any evidence of these conditions?

Yes


No


8. CHECK THE (K853) CRANKSHAFT POSITION SENSOR 5-VOLT SUPPLY CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Turn the ignition off.
2. Disconnect the PCM C1 harness connector.
3. Measure the resistance of the (K853) CKP Sensor 5-Volt Supply circuit between the PCM C1 harness connector and the CKP Sensor harness connector.


Is the resistance below 5.0 Ohms?

Yes


No


9. CHECK THE (K853) CRANKSHAFT POSITION SENSOR 5-VOLT SUPPLY CIRCUIT FOR A SHORT TO GROUND
1. Measure the resistance between ground and the (K853) CKP Sensor 5-Volt Supply circuit at the CKP Sensor harness connector.


Is the resistance above 10k Ohms?

Yes


No


10. CHECK FOR THE (K853) CRANKSHAFT POSITION SENSOR 5-VOLT SUPPLY CIRCUIT SHORTED TO THE (K925) CKP SENSOR GROUND CIRCUIT
1. Measure the resistance between the (K853) CKP Sensor 5-Volt Supply circuit and the (K925) CKP Sensor Ground circuit at the CKP Sensor harness connector.


Is the resistance above 10k Ohms?

Yes


No


11. CHECK THE (K24) CRANKSHAFT POSITION SENSOR SIGNAL CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Disconnect the PCM C1 harness connector.
2. Measure the resistance of the (K24) CKP Sensor Signal circuit between the PCM C1 harness connector and the CKP Sensor harness connector.


Is the resistance below 5.0 Ohms?

Yes


No


12. CHECK THE (K24) CRANKSHAFT POSITION SENSOR SIGNAL CIRCUIT FOR A SHORT TO GROUND
1. Measure the resistance between ground and the (K24) CKP Sensor Signal circuit at the CKP Sensor harness connector.


Is the resistance above 10k Ohms?

Yes


No


13. CHECK FOR THE (K24) CRANKSHAFT POSITION SENSOR SIGNAL CIRCUIT SHORTED TO THE (K925) CKP SENSOR GROUND CIRCUIT
1. Measure the resistance between the (K24) CKP Sensor Signal circuit and the (K925) CKP Sensor Ground circuit at the CKP Sensor harness connector.


Is the resistance above 10k Ohms?

Yes


No