DS4 signal to PCM?

[neo]

I honestly figured I could find this someplace, but not so far. I am trying to understand as specifically as possible, the signal that is fed back from the DS4 to the PCM in a OBDII application. As I understand it is a signal from the optical encoder, so it should be a square wave I am assuming. I also assume it is timed with the engine frequency, some multiple I would presume, like the CKP is 4X pulses for every revolution. I was wondering if anyone has this information, or a wiring schematic for the PCM. I need to know the frequency and the amplitude of the signal so I can replicate it.
My intent is to program an Arduino microprocessor to use the CKP, or some other engine speed signal as a trigger for a replicate signal for simulating the DS4 so I can send that to the PCM can fake it in a DB2 conversion to think there is a DS4. I feel this is pretty doable, and am reasonably versed in the Arduino. Any input is appreciated.
Thanks!
Neo

[convert2diesel]

Neo:

I assume this is for your DS4 to DB2 conversion. I do know that prior to 95, the OBD1 computers were chip driven and that after 96 they were all OBD2. What I don't know is if they went to flashable computers after 96.

I too investigated putting dummy loads on the ecm to fool it into thinking all things were right in its world but kept getting stopped at many points. It probably makes more sense to find a pre-96 ECM and wiring and use something like TunerCat, along with a eprom reader/programmer (can be had for less than 30 bucks), to tune out all fuel related parameters or set the tables well beyond the norm so they don't kick in at all. Takes a little understanding on how the DS4 system works, and a handful of eproms (available at your local JY), but based upon your questions, it looks like you have the chops to do the job.

If your ECM is flashable, John Kennedy may be able to flash an ECM for you, specific to this, using the same methodology. Conversely you could also purchase a software package and cable like EFI Live or TunerPro and do it yourself. Best to purchase a couple of ECMs in case you dynamite one (ask me how I know?).

Essentially all you are trying to do is to set the parameters so that the ECM doesn't set a tier one CEL code and go into limp home mode, buggering up the trans program.

Bill

[neo]

THis is a great solution and great informaiton. I really appreciate this.
Do you know if the 96+ ODB-II EPROM is soldered on, if so, is it possible to desolder it and put a socket on the PCB and then swap them out that way? I have never worked on the code for a PCM/ECU but definetley like to try. My programming background is limited to some basic stuff and some PLC programs so I don't know how different an ECU/PCM will be, but presume there is plenty of info out there to lear from. THen, basically take out the "rungs" for checking the DS-4 data. I am getting three real error codes, one for the "timing" and two other DS-4 codes. I am getting a couple "pending" codes, one or two deal with the trans (fluid temp and one other) but I know the fluid temp is fine cause i have a good guage and it is running in the 150/160 range.
So far, the truck has not triggered "limp-mode" unless of course I disconnect the APP, then it limits the fuel to only allow 1000 rpm max. I could eliminate this by not using the old DS-4 Fuel shutoff solenoid wires to pull in a relay powering the DB2 FSS, but that seemed like the most logical way to handle that. Plus, as an aside, it alows me the security if my engine did try and run away, it would limit it to 1000 rpm as long as it was not related to the FSS.
THanks again! I will research this more

[convert2diesel]

After 96 I have no idea what ECM they used. I suspect they went to a flashable ECM as all the gassers did but am not sure. If its flashable, than you don't have to go into the box at all. Just reflash it with the new program. If it still uses an eprom, than would suspect that going to a pre-95 ECM would be easier as it would be OBD 1 and the software is easier to hack and programming software is cheaper (100 bucks including the definition file). Should have all the necessary outputs for speedo, AC etc., just in an OBD1 format.

They did have a standalone computer for just the tranny in the 93-94 "C" chassis trucks with the 6.5/4L80E with the DB2 pump. Have one in the garage but not the harness. Additionally I don't know if they changed the way the 4L80 worked between 93 and 96 so have no idea if it would work on your trans.

Good luck

Bill

[greatwhite]

After 96 I have no idea what ECM they used. I suspect they went to a flashable ECM as all the gassers did but am not sure. If its flashable, than you don't have to go into the box at all. Just reflash it with the new program. If it still uses an eprom, than would suspect that going to a pre-95 ECM would be easier as it would be OBD 1 and the software is easier to hack and programming software is cheaper (100 bucks including the definition file). Should have all the necessary outputs for speedo, AC etc., just in an OBD1 format.

They did have a standalone computer for just the tranny in the 93-94 "C" chassis trucks with the 6.5/4L80E with the DB2 pump. Have one in the garage but not the harness. Additionally I don't know if they changed the way the 4L80 worked between 93 and 96 so have no idea if it would work on your trans.

Good luck

Bill

OBDII PCM's are part number 16216588.

They are all on board "flashable" chips.

There's nothing removable inside the case for a "normal" user. Essentially, it's all surface mount...