Jeep Grand Cherokee will crank but not start

Check Engine light ON,  Vehicle will crank but not start

2003 Jeep Computer Scan Showed following codes: P0122, P0320 and P1763

As per the error codes mentioned i will provide the details about the codes :----


Starting with  OBD error code P0122 .

• These code is for the throttle position sensor and won't be related to  no start condition which you are facing. 
• OBD code P0122 sets when the voltage signal  from the sensor goes to or near 0 Volts. 
• This code can be caused by the faulty throttle position sensor itself or it's signal wire being shorted to ground. 
• As per our Auto garage repair experience, i will say that most often it's just the sensor itself and replacing it would take care of the code. 

For your 2003 Year model jeep grand Cherokee  the throttle position sensor is mounted on the back of the throttle body and held on with two Torx screws.Its not very difficult to locate and replace.



Moving to the other error code that is P0320 ...............

The OBD error code P0320 can be related to no start problem.
I will explain with more explanation,to make you understand the occurring of these error code.

Its related to Crankshaft sensor. P0320 sets when the engine controller isn't seeing an input from the crankshaft position sensor but it knows the engine is turning.

As per our garage repair experience i will say .........

• The crank sensor goes down into the transmission bellhousing at about the 11:00 position.
• It can be  viewed from behind and it reads off a tone wheel on the flexplate. 
• The purpose of crank shaft sensor is to read the position and speed of the crankshaft.
• Another  main  reason of crank sensor is that it calculates the spark, without it's signal the engine can't start. When you start the engine engine cranks and spark plugs provides required spark, and these spark is sensed by crank sensor and it gives signal to engine thast spark is received.
• But if crank shaft sensor is faulty then it will not sense the spark,even though the spark plugs are working right.

Again this could be the sensor or it's wiring, but it's almost surely the sensor. Crank sensor failures are not uncommon.I will say at our garage we have deal with many vehicle no start issues,due to faulty crank shaft sensor.


Now moving to the another code that is P1763 .............

OBD code P1763 is related to vehicles gear shift issues.

As you have received P1763 code,so first confirm do you actually notice any kind of gear shift issues.


As per our car repair experience i will say the crank sensor won't be related to these other issues. With the TPS or the P1763 you wouldn't really notice a miss. You might notice a hesitation at the exact time the P0122 sets, possibly not.


Related to error code P1763  i will say


The P1763 is indication to monitor the governor pressure transducer in the trans.

• On your jeep vehicle the trans has an electronic governor using a solenoid and a transducer to control governor pressure for upshift and downshift timing. 
• For transducer, it is the plastic pressure sensor mounted off to the right side of the valve body, it's just to the right of the filter when the pan is removed. 

This code could be caused by the transducer or it's wiring, but the transducer is a common repair and will almost surely be your issue.

So without your vehicle running,you cannot confirm the actual gear shift issues.

What i suggest, is replace the crank sensor and get it running again.
Then  clear the codes and wait to see if the engine light comes back on.
If the Engine light is again ON,then re-scan the vehicle to see if same error codes are coming up or not.
If yes then governor transducer or the TPS are to be inspected and replaced.
but mostly as per our regular vehicle repair deals i think these codes will get cleared once the vehicle starts running.



Hope these details will help you.
Thanks.

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Crankshaft Position Sensor Operation?

The details are as follows :---

Crankshaft Position (CKP) Sensor

OPERATION

7X Crankshaft Position Sensor
EXCEPT 3.5L (VIN H) AND 3.8L ENGINES

The 7X Crankshaft Position (CKP) sensor provides a signal used by the ignition control module. The ignition control module also uses the 7X CKP sensor to generate 3X reference pulses which the PCM uses to calculate RPM and crankshaft position.

The 7X CKP sensor is the most critical part of the ignition system. If the sensor is damaged so that pulses are not generated, the engine will not start!

The 7X CKP sensor is a Hall-Effect switch, mounted on the outside of the engine block, close to the crankshaft. The interrupter ring is a special wheel cast on the crankshaft that has seven machined slots, six of which are equally spaced 60 degrees apart. The seventh slot is spaced 10 degrees from one of the other slots. As the interrupter ring rotates with the crankshaft, the slots change the magnetic field. This will cause the 7X Hall-Effect switch to ground the 3X signal voltage that is supplied by the ignition control module. The ignition control module interprets the 7X ON-OFF signals as an indication of crankshaft position. The ignition control module must have the 7X signal to fire the correct ignition coil.

The 7X CKP sensor uses a two wire connector at the sensor and a three-way connector at the ignition control module.

24X Crankshaft Position Sensor
EXCEPT 3.5L (VIN H) AND 3.8L ENGINES

The 24X Crankshaft Position (CKP) sensor is used to improve idle spark control at engine speeds up to approximately 1250 RPM. The 24X CKP sensor contains a Hall-Effect switch. The magnet and Hall-Effect switch are separated by an air gap. A Hall-Effect switch reacts like a solid state switch, grounding a low current signal voltage when a magnetic field is present. When the magnetic field is shielded from the switch by a piece of steel placed in the air gap between the magnet and the switch, the signal voltage is not grounded. If the piece of steel (called an interrupter) is repeatedly moved in and out of the air gap, the signal voltage will appear to go ON-OFF-ON-OFF-ON-OFF. Compared to a conventional mechanical distributor, the ON-OFF signal is similar to the signal that a set of breaker points in the distributor would generate as the distributor shaft turned and the points opened and closed.

In the case of the electronic ignition system, the piece of steel is a concentric interrupter ring mounted to the rear of the crankshaft balancer. The interrupter ring has blades and windows that, with crankshaft rotation, either block the magnetic field or allow it to reach the Hall-Effect switch. The Hall-Effect switch is called a 24X Crankshaft Position sensor because the interrupter ring has 24 evenly spaced blades and windows. The 24X CKP sensor produces 24 ON-OFF pulses per crankshaft revolution.

The 24X interrupter ring and Hall-Effect switch react similarly. The 24X signal is used for better resolution at a calibrated RPM.

The 24X CKP sensor clearance is very important. The sensor must not contact the rotating interrupter rings on the crankshaft balancer at any time, or sensor damage will result. If the balancer interrupter rings are bent, the interrupter ring blades will destroy the sensor. If the 24X CKP sensor replacement is necessary, the crankshaft balancer must be removed first (as outlined in of this guide). When reinstalling the balancer, torque the balancer attachment bolt to specification. This is critical to ensure the balancer stays attached to the crankshaft. If the 24X CKP sensor assembly is replaced, check the crankshaft balancer interrupter rings for any blades being bent. If this is not checked closely and a bent blade exists, the new crankshaft position sensor can be destroyed by the bent blade with only one crankshaft revolution!

Dual Crankshaft Position Sensor
3.5L (VIN H) ENGINE

The Crankshaft Position (CKP) sensor used on this engine is actually two sensors within a single housing. Each sensor has a separate power, ground and signal circuit. The PCM supplies 12 Volts to both sensors. The PCM provides the ground path, or sensor return circuit, from both sensors. These power and ground circuits are also connected to the Camshaft Position sensor. Two separate signal circuits connect the CKP sensor and the PCM. The PCM can use three different modes of decoding crankshaft position. During normal operation, The PCM performs an Angle Based calculation using both signals to determine crankshaft position. The dual sensor allows the engine to run even if one signal is lost. If either signal is lost, the PCM switches to a Time Based method of calculating crankshaft position. If the system is operating in Time A mode, the PCM is using only the signal from Sensor A. Time B indicates that the Sensor B signal is being used. If the lost signal is restored, the PCM will continue to operate in Time based mode for the remainder of the current key cycle. The PCM will revert back to the Angle mode on the next start if the fault is no longer present. A technician's scan tool can display the Crank Position Sensing Decode Mode. A problem with either Sensor A or Sensor B will set a Diagnostic Trouble Code.

The Crankshaft Position Sensor Learn Procedure must be performed after replacing the CKP sensor. Even if the original sensor is reinstalled, the Learn Procedure must be performed. This procedure must be performed with a scan tool. The crankshaft position system variation compensating values are stored in the PCM non-volatile memory after a learn procedure has been performed. If the actual crankshaft position system variation is not within the crankshaft position system variation compensating values stored in the PCM, a diagnostic trouble code may set.

The Crankshaft Position System Variation Learn Procedure should be performed after any of the following conditions:

DTC P1336 is set

The PCM has been changed

The PCM has been reprogrammed

The engine has been replaced

The crankshaft has been replaced

The Crankshaft Position Sensor has been replaced

3.8L ENGINES

On the 3.8L engines, the Crankshaft Position (CKP) sensor provides a signal used by the ignition control module to calculate the ignition sequence. The ignition control module also uses the crankshaft position sensor signals to initiate 18X and 3X reference pulses which the PCM uses as reference to calculate RPM and crankshaft position.

The dual crankshaft position sensor used on 3.8L engines is secured in an aluminum mounting bracket and bolted to the front left side of the engine timing chain cover, partially behind the crankshaft balancer. A 4-wire harness connector plugs into the sensor, connecting it to the ignition control module. The dual crankshaft position sensor contains two Hall-Effect switches with one shared magnet mounted between them. The magnet and each Hall-Effect switch are separated by an air gap. A Hall-Effect switch reacts like a solid state switch, grounding a low current signal voltage when a magnetic field is present. When the magnetic field is shielded from the switch by a piece of steel placed in the air gap between the magnet and the switch, the signal voltage is not grounded. If the piece of steel (called an interrupter) is repeatedly moved in and out of the air gap, the signal voltage will appear to go ON-OFF-ON-OFF-ON-OFF. In the case of the electronic ignition system, the piece of steel is two concentric interrupter rings mounted to the rear of the crankshaft balancer.

Fig. Because of their different blade and window configurations, the two Hall-Effect switches generate 18 and 3 CHP pulses for each crankshaft revolution-3.8L Engines

Each interrupter ring has blades and windows that either block the magnetic field or allow it to close one of the Hall-Effect switches. The outer Hall-Effect switch produces a signal called the CKP 18X because the outer interrupter ring has 18 evenly spaced blades and windows. The CKP 18X portion of the crankshaft position sensor produces 18 ON-OFF pulses per crankshaft revolution. The Hall-Effect switch closest to the crankshaft, the CKP Sync portion of the sensor, produces a signal that approximates the inside interrupter ring. The inside interrupter ring has 3 unevenly spaced blades and windows of different widths. The CKP Sync portion of the crankshaft position sensor produces 3 different length ON-OFF pulses per crankshaft revolution. When a CKP Sync interrupter ring window is between the magnet and inner switch, the magnetic field will cause the CKP Sync Hall-Effect switch to ground the CKP Sync signal voltage supplied from the ignition control module. The CKP 18X interrupter ring and Hall-Effect switch react similarly. The ignition control module interprets the CKP 18X and CKP Sync ON-OFF signals as an indication of crankshaft position, and the ignition control module must have both signals to fire the correct ignition coil. The ignition control module determines crankshaft position for correct ignition coil sequencing by counting how many CKP 18X signal transitions occur, that is, how many ON-OFF or OFF-ON, during a CKP Sync pulse.

This will help.

Thanks.