Ok I got a tough one. 2002 Dodge Durango

1. Turns over just fine but will not start.
2. Odometer blinks and displays no buss.

CHECKS

I have unplugged the throttle position sensor and the cam position sensor and checked the three plugs for voltage with the igintion switch on.

Results:

5v reference WITH the connector UNPLUGGED.

I have disonncected the battery first unplugged the power control module all three connectors reconnected the battery. Then unplugged the throttle position sensor and the cam position sensor and checked the three plugs for voltage with the igintion switch on.

Results:

2.1 v reference WITH the connector UNPLUGGED.


Questions:

1. Should I have unplugged the connectors on the throttle position sensor and the cam position sensor before checking for the reference voltage or left them plugged in?

2. Should I find the 2.1v with the power control module unplugged?

 

no bus means that the PCM (powertrain control module) is not communicating with the dashboard correctly, afaik the tps and cam sensors only communicate with the PCM which then relays any necessary information to to the dashboard.

5v at the TPS is the correct reading w/ the module connected (i believe this should be with the throttle plate held all the way open tho, not sure how you are taking the reading) although im not sure why you are checking for this,

and i would expect you to get 0 volts at any sensors w/ the PCM disconnected since the PCM is supposed to be regulating the 12v down the 5v sensor rail before it sends it out to the sensors.

 

do you hear the starter motor when you turn the ingnition?

 

yes he does

 

Ok per the directions below I am trying to isolate the problem causing the NO BUS
fault displayed on the dash where you normally see the odometer reading. Yes I do hear the starter turning and the entire engine turning over. In fact it sounds exactly like what you would expect to hear if you had no spark or no fuel.

So in trying to follow these instructions I checked to see if I had 5 volts reference voltage with the connectors unplugged.

Why? Because I wanted to make sure the 5 volts was getting to the sensor in question.

I also checked for the same 5 volt reference with the Power Control Module unplugged.

Why? Because I was trying to verify the five volt reference siganl was coming from the Power Control Module. For the record I expected to get zero volts. What baffled me was I got 2.1 volts with the Power Control Module unplugged. So now I am wondering if the 2.1 volts might indicate where the problem is? Anyone? Buelar? Buelar?

Problem 1 of 6: 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 CCD 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 second after the short is removed. Using a 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 6: 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 CCD 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 second after the short is removed. Using a 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.

Problem 3 of 6: The 5v power supply from the Powertrain Control Module (PCM) is shorted due to a shorted Manifold Absolute Pressure (MAP) Sensor.

Test & Fix: If the 5v power supply circuit is shorted to ground, the CCD 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 second after the short is removed. Using a DVOM or labscope, measure the voltage on the 5v reference wire (5v power supply) at the Throttle Position Sensor (TPS) or Manifold Absolute Pressure (MAP) Sensor. If 5v is not present, unplug the MAP 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 MAP sensor.
Problem 4 of 6: The 5v power supply from the Powertrain Control Module (PCM) is shorted due to a shorted Throttle Position Sensor (TPS).

Test & Fix: If the 5v power supply circuit is shorted to ground, the CCD 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 second after the short is removed. Using a DVOM or labscope, measure the voltage on the 5v reference wire (5 volt power supply) at the Throttle Position Sensor (TPS) or Manifold Absolute Pressure (MAP) Sensor. If 5v is not present, unplug the TPS. 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 TPS.

Problem 5 of 6: The 5v power supply from the Powertrain Control Module (PCM) is shorted due to a shorted wire.

Test & Fix: If the 5v power supply circuit is shorted to ground, the CCD 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 second after the short is removed. Using a 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 all sensors that are connected to the 5v power supply and disconnect the PCM. Check if either 5v power supply circuit is shorted to ground using a DVOM. If the circuit is found to be shorted to ground, repair the wire and the cause of the short.

Problem 6 of 6: The 5v power supply from the Powertrain Control Module (PCM) is shorted due to a shorted Governor Pressure Sensor.

Test & Fix: If the 5v power supply circuit is shorted to ground, the CCD 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 second after the short is removed. Using a 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 large round connector on the driver's side of the transmission. 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, remove the transmission pan and check for shorted wiring inside the transmission. If the wiring is OK, replace the Governor Pressure Sensor.

 

problem 1,2): i have heard of the crank and/or cam sensor shorting to ground and taking down the entire sensor bus, must have been having a moment to not think thats what you were testing, my bad.

as for 3,4,6 i have never heard of but if this came out of a FSM its accurate.

i would suspect that you since you have the correct voltage w/ the PCM connected that there is a short into the 5v rail which is giving you the 2.1 volts, i dont know where that would be, but if it were me that is what i would be looking for.

you could also PM a user by the name of master tech who should be able to narrow it down more for you since he is a dodge tech for a living.

im sorry i couldnt be any more help

 

shrpshtr325 thanks for the reply!

Ok I tried the cam sensor and the crank sensor and really thought I had it fixed alas, the old dodge ran 16 miles and quit on me.


As for the mysterious 2.1 Volts I was able to trace the source to the transmission computer. I realize that is not the correct mopar term. Perhaps someone can correct that for me?

So that brings up another question. Should the transmission computer be supplying 2.1 Volts? How about it master tech? Is that the next piece I can expect to replace?

 

Try putting a bag of ice on the PCM and see if that gets it to start (i know it sounds stupid, but here is reason). If it starts and runs, an internal component in the PCM is bad and overheating. I just had to replace my PCM 2 months ago, and had identical symptoms as you are describing.

 

the transmission computer (usually referred to as the TCM or transmission control module) should supply voltage to the transmission sensors, and i would expect to recieve data from the tps, cam and crank sensors to determine when to shift based on engine speed, road speed (recieved from the abs system) and engine load (tps data). however some or all of this data could be sent to the TCM by the PCM instead of it monitoring directly so the exact path is unknown to me.

 

When my pcm went out it would work until the engine heated up and the pcm started to overheat and then I got the no bus error. I just replaced my pcm with another one and everything worked fine again. I think I got it at autozone and they had to find one with matching numbers. I still have my old bad one that overheats, but it was for the 5.9 not the 4.7 so you couldnt even use it to test.