duratothemax

so the Cummins ECM doesnt have its own MIL-request wire?

So is it like there are two ECM's so to speak? There is the Cummins ECM, and then it speaks to another Dodge ECM...then the dodge ECM drives the transmission and worrys about sending data to the cluster, and making the cummins ECM talk to the rest of the body...? Seems like kinda a clumsy roundabout way of doing it...why not just have the CTD ECM do all of that directly? I guess its sort of the same situation as the Dmax tho, the Allison has its own separate transmission computer (which is the same one as used on all allison transmissions)...BUT the allison is programmed to not only talk to the dmax ECM, but it can also talk to the GM body computer directly to relay trans temp data to the instrument cluster, MIL request wire, and PRND321 display status along with reverse light data etc...

is it like that or is it something different???

what data protocol does the cummins ECM speak? I would think at the very minimum it would speak sae J-1939 CAN 1, because that is the accepted standard in the medium duty world. Does it also speak something else to the OBD port for EPA compliance? Usually its J1850 VPW (GM), J1850 PWM (ford), ISO9091 (asian vehicles), and then chrysler uses something different, but pretty similar to the ISO bus used by asian and european vehicles...all of these "basic" slow data busses must be present to allow generic OBD code readers to diagnose emmissions problems, not just the chrysler DRB tool or hte GM Tech 2.

just out of curiosity, how many pins does a dodge OBD port have? The bare minimum should be Power, 2 ground pins, and the 4th pin broadcasts the standard OBD-compliant basic data bus.......

ben

5.9Excursion

Yes, you described it correctly. The engine has its ECM. The truck has a PCM for trans control, driving the cluster, talking with all the other body electronics, etc. There is no MIL control wire from the engine ECM.

duratothemax

ahh ok....interesting....so I guess your only option would be to use the dodge PCM....unless you installed separate sensors on the engine just to drive the cluster...how does the ford cluster interperate stuff from the engine? Is it like the GM clusters where everything from oil press to trans temp to rpm to fuel level comes in over a single data bus wire, or are there descrete wires for each guage? Sorry I just started reading this thread and havent really followed it from the first pages...so I might be asking things that were answered on the second page.

ben


EDIT: another quick question....does the cummins ECM and engine "need" the dodge PCM to "survive"? Does anyone have the pinouts for the cummins ECM itself? Only potential problem I see is if the dodge PCM is needed to allow the cummins to start because of security stuff (like GM's VATS, I think chryslers is sentrykey or something??)

second EDIT: nvmind I think I found most of the answers on pages 9 and 10

5.9Excursion

No this wasn't asked or answered earlier. I believe all the sensor signals from the V10 engine were read by the Ford PCM and that drove the cluster with individual wires (I'll have to look again to be sure).

The cummins ECM uses CAN-BUS J1979 I believe (for communication with the Smarty or a DRB scanner). It also uses a PCI-bus for communication with the PCM and other components on the truck. Here's some info out of the service manual on the PCI-bus communication...

The DaimlerChrysler Programmable Communication
Interface (PCI) data bus system is a single wire
multiplex system used for vehicle communications on
many DaimlerChrysler Corporation vehicles. Multiplexing
is a system that enables the transmission of
several messages over a single channel or circuit. All
DaimlerChrysler vehicles use this principle for communication
between various microprocessor-based
electronic control modules. The PCI data bus exceeds
the Society of Automotive Engineers (SAE) J1850
Standard for Class B Multiplexing.

Attached is the pinout of the dataport connector from the manual... Pins 7 & 12 communicate with the ECM. The TCM is the dodge transmission control (normally refer'd to as the PCM). Terminology gets confusing because the manual also covers gassers...

5.9Excursion

It's called the SENTRY KEY IMMOBILIZER MODULE

DESCRIPTION

The Sentry Key Immobilizer Module (SKIM) contains
a Radio Frequency (RF) transceiver and a central
processing unit, which includes the Sentry Key
Immobilizer System (SKIS) program logic. The SKIS
programming enables the SKIM to program and
retain in memory the codes of at least two, but no
more than eight electronically coded Sentry Key
transponders. The SKIS programming also enables
the SKIM to communicate over the Programmable
Communication Interface (PCI) bus network with the
Powertrain Control.

Not sure when it came out or if it was only an option. My engine didn't have it so I didn't have to worry about it.

duratothemax

when you say J1979...did you mean J1939? J1979 simply refers to the OBD standard protocol, the connector that must be used, and other limitations and requirments that must be met for all vehicles sold in the US....its not an actual databus, whereas J1939 is an actual data bus spec, mostly used as high speed comms for tracotr trailers and medium duty apps. This makes sense for the Cummins ECM to speak that because of its medium duty original application. Same goes for teh Allison trans in teh GM pickups...it speaks J1939 just the same because of its original intended app...

The CTD ECM speaks J1939 (the only thing it knows) to the dodge PCM...J1939 isnt allowed in the light duty EPA OBD 2 requirments so the dodge PCM I think just basically acts as a gateway between the CTD ECM and the dodge truck/obd compliance....thats the way Im reading it I think???

5.9Excursion

My mistake, yes I meant J1939. That's the same communication that my transmission controller will accept. I'm trying to get it upgraded to the latest revision so I can directly input this communication to the controller. That way, engine rpm, coolant temp, boost pressure, intake air temp, etc will all be displayed on my laptop realtime (the controller can be a datalogger as well).

I would agree that the dodge PCM is just acting as the middle man in the communication between J1939 and the OBD communication. So what would happen if I hook up my regular OBD code reader to this port? Does it just speak on the PCI bus? If so, I imagine it wouldn't work since the ECM isn't the dominate node on the PCI bus?

duratothemax

ok I found the pinouts and wiring diagrams for the PCM (not ctd ecm) and it appears that it does hardly anything. The CTD ECM has its own PCI bus output, which could technically be hooked directly into a dodge cluster or OBD port. It seems all the PCM does on the cummins trucks is enable this "transmission relay" thing, and distribute power/IGN/run stuff....which could also just be wired directly into the cummins ECM...

Im reading the service manuals over cause I like learning about this stuff and hopefully Ill be able to make sense of it, and Ill look at the ford service manuals too...the dodge system confuses me tho....no offence but its a rats nest, hugely cluttered and confusing as @*#$ system compared to the simple and logically integrated GM electrical systems and data busses, which Im used to messing around with. I think im slowly making sense of it all tho...Ive got some work to do now but I will take a look at it more tonight and try to understand it better, because as I said I get a kick outta this wiring stuff and Id like to help you as much as I can...

Ben

duratothemax

ok, yes at this point im 97% confident you can ditch the dodge PCM altogether and just [obviously] keep the CTD ECM...

dodge PCM controls fuel heater, starter, and that trans contorl relay, but those are driven from signals via the CTD ECM, so you can just mimick that witha simple 12v relay.

You can pick up the wires that need to go to the OBD port directly from the cummins ECM

On the ECM C2 connector...

Pin 28 (should be a white/ppl wire) is the PCI bus wire.
Pin 16 is the SCI transmit wire (pink)
Pin 19 is the SCI receive wire (white lt green)

PCI bus seems to be the low speed data bus that transmits info to the instrument panel cluster. At this point Im not sure how you would decode this info (oil press, rpm, etc) into something the ford cluster could understand, but ill do some more resarch..

SCI seems to be the high speed data bus that the Smarty or whatever reprograms the ECM with. So you will need to plumb all of these wires from te CTD ECM directly to the proper locations on the existing ford OBD port.

5.9Excursion

I appreciate anything you can figure out on this. If you didn't catch it earlier on in the thread, I don't have a dodge PCM at all. Just as you said I am using the signals from the ECM to run my fuel heater (w/ a relay). I am using the ford circuity to energize the starter (w/ a relay). Don't need the transmission relay thing since I have the standalone tranny controller.

I currently have the SCI wires and the PCI bus wire from the ECM run to it's own data port under the dash. I left the ford dataport installed seperate.

The cummins has it's own engine wiring harness that connects to everything on the engine and the ECM. This harness has two connectors that connect the engine wiring harness to the truck. Those are C108 & C110, so all my connections were made right there (no splicing into wires this way).

My trans controller will accept analog or digital inputs and can then drive outputs (analog signals, PWM, etc). It will also allow the input of the parameters using CAN-BUS J1939. So if I can get all of these signals into the controller, I could send outputs out of it based upon this information (possibly a signal to drive the tach for example).

duratothemax

ok so let me just get this straight...your only problems/roadblocks left are controlling the check engine light and engine guages??

ben

5.9Excursion

Currently the only gauge that doesn't work is the tach. I just today (according to the wife) got a box from dakota digital that supposedly will turn the crankshaft position signal into a tach signal for me.

I would love to get the Ford SES light to function based upon if any codes get set in the cummins ECM. Right now this light is controlled by the ford PCM and is on obviously (haven't cut the wire yet).

I would like to get all the engine parameters into my trans controller for datalogging purposes and just because the display looks cooler when all the gauges are working.

Current codes are related to fuel level signal (working on this one yet) and J1850 ckt short to ground. This is related to the PCI bus and how the ECM isn't the dominate node of communication I think. I tried terminating the PCI circuit but I still have the code.

duratothemax

hmmm unfortuantly I dont think you will be able to get the SES light working...the only way its turned on (which I thought was odd) is through the PCI bus sending a data signal to the dodge instrument cluster. If you wanted to get ghetto, you could hack up a dodge IPC and tap into the wiring for the SES light on the dodge cluster..

How did you get the oil press and fuel level guages working?

Are you sure the PCI bus needs terminating tho ? Its a single wire protocol IIRC, floats at 7 volts and is pulled to ground when a bit of data is broadcast (something like that I think), much like GM's Class 2 data. I THINK the only bus that needs terminating is the high speed SCI bus, which has two wires. The termination is to reduce crosstalk and interference between the two bus wires.

Like I said tho, im not 100% sure on any of this..

5.9Excursion

I'm using the ford instrument cluster. All ford gauges are driven by the ford PCM which is receiving the sensor signals the same as before. I mounted the ford coolant temp sensor and oil pressure "switch" on the engine so all gauges work just as they did before.

I read about the PCI termination in the manual, it didn't work though.

What you said has me thinking though, the manual said the dodge PCM is the main node if you will for the PCI bus. So maybe it is what causes the one wire to float at 7 volts. If it isn't there (and it isn't), the one wire is at 0 volts, and causes the cummins ECM to see this as a short to ground somewhere?

Maybe I can just put 7 volts on the line and the code will go away?

xtoyz17

From what I've read, and what I *think* I understand that makes sense. Radioshack probably has something you could rig up to set a voltage output.