Monday, February 18, 2013

Dodge Ram:Charging system, Transmission, A/C and Cruise Control Stopped Working

Dodge Automatic Transmission , slow to shift when cold but all gears work fine

Alternator already replace with no difference in problem.




On dodge vehicle models the charging system, transmission, a/c and cruise control functions all are controlled by PCM. PCM is also called as  powertrain control module. PCM  is the module mounted behind the airbox on the firewall.


  • Now as per what the details are mentioned  transmission shifts and if the fuel gauge still works we can assume the PCM is still up and functional. If the fuel gauge did stop working at the same time as the tach and charging system then most probably the issue is faulty PCM.Still it has to be checked,but mostly its PCM.

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  • Other possibility,it can be faulty alternator,but its said that alternator is replaced,but still alternator will not work, 

REASON WHY?
The alternator receives voltage from the ASD relay and then charging is controlled by the PCM. The PCM turns the ASD relay on only when it knows the engine is running.

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  • Other thing can be faulty Crank Sensor.Which i think is most possible.

REASON WHY?

On the timing cover just above the crank damper is the crankshaft position sensor. The crank sensor runs off the crank damper and tells the PCM the engine's speed. When the PCM sees a signal from the crank sensor it will turn the ASD relay on and the alternator can charge. The crank sensor is also what allows the tach to work, it's the only input for engine speed.

As per your problem also tach and charging system stopped working together
Also  tach and charging functions both rely on the crank sensor's signal and these were the only two things lost at the same time it's very likely that you have a bad crank sensor.


HOW TO TEST CRANK SENSOR?

It can be tested with a digital voltmeter, although it is somewhat hard to get to in the close quarters. If you don't have the means to test it then I would do a visual inspection of the wiring and connection, and replace the sensor if all looks ok.


DETAILS ABOUT PCM AND TIMING COVER?


The PCM is the powertrain control module already mentioned before.Its a silver rectangular module mounted on the firewall behind the airbox. It has three 32-way electrical connectors. This is the best indication to locate it.

The timing cover is the thin black steel cover on the front of the engine. The crank damper is the large pulley on the front of the engine, easiest seen from the bottom. It's the largest pulley and is the one coming directly from the engine itself.



CRANK SENSOR LOCATION AND WIRING DIAGRAM:

You will see some wires coming from a harness at the front of the motor leading down past the waterpump  going to the sensor.

The wiring to the crank sensor will run right down past the water pump area and the sensor mounts to the timing cover below the pump area. The crank sensor is the only thing electrical up there.

View the actual picture of a 12 valve Cummins with an arrow drawn to the crank sensor wiring.

12 valve cummins


Mostly it seems faulty crank sensor but if all control function stopped working then it can also be faulty PCM.
These details will help you.
Thanks.


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