Cranks But No Start Harness plug?

[Gelder]

My 05 Ram 2500 has an wierd issue, It cranks and wont start, in this condition I have no fuel gauge/amp meter/ lift pump. If i unplug the big harness connector by the cowl while the key is in the on position then plug it back in, everything comes on and the truck starts. I have to do this everytime to start the truck. I found a similar post from the past and a bad ground was the issue but I wasnt so lucky. Checked them all and they are good. Has anyone ran into this issue? Im crossing my fingers someone can help. Thanks Bob. Could it be the ECM?

 

[TCDiesel]

NO its not the ECM ,Its the PCI or J1850 You have a bad connection. PCI (Programmable channel interface)

 

[Gelder]

Since I only got 1 response i thought i would post the solution, it may help someone out in the future.

My problem was a bad clutch fan, it seems the ECM wont come on if the clutch fan is shorted out.

Had no Fuel gauge, Amp gauge, no lift pump, no intake heaters coming on. Did have codes for fan but never thought a fan could cause a no start condition so i was looking at other things thinking it was 2 different problems. Unpluged fan Engine starts. Replaced Fan.

 

[TCDiesel]

Thanks for the update.....

 

[Prairie Dog]

Good to know - I wouldn't have ever thought there would be a connection between the fan and a no-start either.

 

[SDrake]

Good to know - I wouldn't have ever thought there would be a connection between the fan and a no-start either.

WOW!! I seriously think this truck may drive me absolutely crazy. Electrical gremlins. I like mechanical things because they help me escape the electonics world. this truck is dragging me back into electronics. I am going to have to quit thinking in terms of the mechanics if I want to have a long term relationship with this rig.

 

[sag2]

Here is the STAR case from 2005. When the 5v gets shorted by the fan the ECM will not communicate. Had you had a scan tool you would have seen a no response from the ECM. I used to just cut the 5v going out of the ECM when I had a no response and powers and grounds were good. It was a quick way to verify 5v was not shorted.



Case Number K89793694

Vehicle Issue No Start, The DRBIII Shows No Response From The ECM. ;Engine sensors (such as the Engine Coolant Temperature sensor) have 12 volts at the 5 volt supply circuit. The ECM has good power supply and ground.

System or Component Engine Cranks,No Shift / Will not Shift Up or Down;Customer Concern (No DTCs),No Response;ECM;Yes - Intermittent

Recommendation Disconnect the electronic fan clutch connector and check if ECM response returns and the engine starts. Replace the fan clutch assembly if normal operation returns with the fan clutch disconnected.



Modification Date 05/27/05 11:29 AM