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2001 Dodge Ram Van 2500 Question: "No bus"-Message in Odometer

 

Question

TimMoellenberg, 5.2L V8, Miami Beach, FL, November 18, 2009, 03:19
 Rookie

How can i check the pcm-module for correct function? Is the pcm-module the problem or are any other sensors the reason for this message?

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    backyard tech November 18, 2009, 04:35
     Master

    Symptom: Engine will not start. Gauges are inoperative. "No BUS" message displayed on odometer.



    System: Body/Chassis Electrical, Emissions/PCM/Fuel, Engine Electrical



    Codes: N/A



    Problem 1 of 2: The 5v power supply from the Powertrain Control Module (PCM) is shorted due to a shorted Crankshaft Position (CKP) Sensor.



    Test & Fix: If the 5v power supply circuit is shorted to ground, the bus is unable to transmit messages and the Powertrain Control Module (PCM) appears to be dead. The PCM is not damaged when the 5v power supply gets shorted to ground, but does need to be reset by turning the key off for 10 seconds after the short is removed. Using a Digital Volt Ohm Meter (DVOM) or labscope, measure the voltage on the 5v reference wire at the Throttle Position Sensor (TPS) or Manifold Absolute Pressure (MAP) sensor. If 5v is not present, unplug the Crankshaft Position (CKP) Sensor. Turn the key off for 10 seconds. Turn the key on and measure the voltage on the 5v power supply circuit. If the voltage is now 5v, replace the CKP sensor.



    Problem 2 of 2: The 5v power supply from the Powertrain Control Module (PCM) is shorted due to a shorted Camshaft Position (CMP) Sensor.



    Test & Fix: If the 5v power supply circuit is shorted to ground, the bus is unable to transmit messages and the Powertrain Control Module (PCM) appears to be dead. The PCM is not damaged when the 5v power supply gets shorted to ground, but does need to be reset by turning the key off for 10 seconds after the short is removed. Using a Digital Volt Ohm Meter (DVOM) or labscope, measure the voltage on the 5v reference wire at the Throttle Position Sensor (TPS) or Manifold Absolute Pressure (MAP) sensor. If 5v is not present, unplug the Camshaft Position (CMP) sensor. Turn the key off for 10 seconds. Turn the key on and measure the voltage on the 5v power supply circuit. If the voltage is now 5v, replace the CMP sensor.

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    Visitor, March 24, 2011, 16:34

    After replacing the crank senso the vehicle runs for 5- 10 minutes and stalls. It re starts instantly with no codes???

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  • Answer #2

    Visitor, February 02, 2011, 08:28

    IT MEANS THAT THE COMPUTER WIRES ARE NOT GETING A GOOD CONNECTION. TRY WIGGLING THE WIRES AT THE PCM

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