hi guys

did a motor swap - 01 dodge ram 2500 4x4 auto trans 5.9L - removed that motor for a 01 dodge ram 2500 2 wheel drive , auto trans 5.9L

went to crank it over which it did turn, but did not start - noticed no fuel pressure - checked the fuel relay , it does get the + signal from the ign switch, but no neg signal from the pcm - of course i can jumper it and get fuel pressure

i dont think we are getting any spark either - I cranked and sprayed some fuel down the intake hoping for at least 1 pop

inside gauges are not moving, and my mileage flashes and then says "no bus" - any thoughts , i have the PDF manuel but it doesnt seem to be helping

 

you pinched one of the wires for a sensor or didnt plug a sensor in..probly the crank sensor or pick up coil..or you broke the crank sensor putting it in...

 

What you've got going on there is a failsafe event has occurred thus tripping the ASD relay. As a result, this kills all power to the entire EFI system- no spark, no fuel etc etc.

Same for the NO BUS issue- same failure mode.

What will trip that is:

CKPS: if the five volt supply line has SHORTED to ground- it will not only kill the PCM but, it will also produce the no BUS error.

Same thing can be said of the CPS.

HOWEVER, it can be many other things that will also lead to this same exact problem.

First thing that comes to mind when swapping an engine out is that, the grounds must be removed in order to rid the old engine. Chances are, the PCM is not grounded or, another system level ground was left undone.

Go through, check the head grounds to firewall are attached and all the tiny AWG wires on the drivers side inner fender wall. Those are the PCM grounds.

Check the wiring harnesses for the CKPS and CPS for cuts, nicks, thus exposed base metal grounding out the 5-volt supply line. IF that's shorted, it kills power to everything, not just the PCM but, the ABS, the CLUSTER etc. Everything is tied into that CKT in one way or another so, if it's shorted, it's going to take a lot of other systems out with it.

I would start there.


CM

 

I'll check that, we did end upmcutting those wires on the old motor, does the commuter need to then be reset? Also just for a test, could I unplug the sensors to see which one? I don't own a scanner but if u think that it would give me a trouble code I could go buy one

 

Sounds like there's your problem- cut wires that weren't reconnected. The PCM is already reset once all power is removed. If you pull the sensors completely, it will not start but, your cluster will at least power on providing that you reconnect all grounds.

If nothing visible is shorted, it simply may be that all it is is a no power condition due to an OPEN CKT. If and when the PCM is not seeing power at any one of the inputs or, any power at all, no power to the EFI system will be measured and, no codes will be logged due to no power to keep the memory alive.

CM

 

Those wires did get reconnected, but I guess we need to double check to be 100% sure they are correct.

My cluster does have indicator lights on, but I assume that's different.

Would you happen to know, if I could test for voltage at the cpm for both of these sensors, input and return for them...what color wires I should be looking for?

Also ckt, stands for ? Crank position sensor?

If we unplugged that sensor that should create an open condition

 

I disconnected the crank sensor, got 2.5 volts at the sensor plug going across vt/wt which is 5 volt supply from cpm and bk/lb with is sensor ground

 

Should measure 5-volts DC and, it must be left IN CKT in order to measure it accurately. You must backprobe the connector in order to obtain an accurate reading to the sensor. What is backprobing? Just use either the long meter probes or, a paperclip attached to pos. Simply insert the probe FROM THE REAR of the connector. NEVER measure from the front of the connector shell as one slip with a probe and you'll short HOT (+) to ground. Dead short- not good. So, ALWAYS backprobe.

NOTE: If and when you want to measure CKPS output: you can NOT obtain an output voltage on the CKPS without the truck running and using an analog meter. For, it pulses voltage according to the square notch outs at the flywheel making it impossible to hold the reading on a digital type of meter. HOWEVER: what I have done (it works sometimes) is, you SLOWLY rotate the engine (at the crank) very slowly while someone else monitors the analog meter. This does work- sometimes. I've done it once but, I also had trouble doing this on another vehicle where, I could not capture the reading as it went by much too fast. It's just a ON/OFF pulse. Best method is to use a good quality scan tool that has the ability to monitor the CKPS output.

Acronyms:

CKT: circuit
CKPS: Crankshaft Position Sensor
CPS: CAMshaft Position Sensor


CM