Conversion from DS4 to DB2

[buddy]

If you disable the flags, then it shouldnt go into limp mode and just run on one input. Just like I disable the boost code so it ignores the defueling that would normally happen and it never sets DTC78.

 

[ak diesel driver]

wouldn't you run the risk of runaway then?

 

[bobbiemartin]

wouldn't you run the risk of runaway then?

Only if the throttle return spring broke.

 

[buddy]

The PCM will have no real control of the fuel rate, we would just be using the TPS input for tranny shifting. I suppose you could still use the ESO circuit and wire it up into the DB2 ESO and disabling the APP DTCs wouldnt stop it from shutting off fuel. And intially I would still try leaving the APP1 DTCs active so it would tell you if the TPS was out of tolerance. The APP and TPS have very similar voltage ranges so it should work just fine.

 

[WarWagon]

Not easily. I think GM was worried that the APP failed, someone would just jump the wires and be able to use a defective APP. My guess is they were worried about runaway acceleration. Anyway, it uses 3 differently scaled APP inputs. They must match or it sets a code. So that is why you would need some sort of circuit to split the signal into the 3 different APP signals. There really is no easy way to use 1 APP signal on the PCM.

Think of how the APP sensor would fail - drop outs and erratic readings including shorted or partially shorted wires. Thus you need two sensors to verify the APP position and prevent one failure for giving a false WOT reading for example. No way to failure check just one sensor for all possible failure conditions. Run a bypass was the least of their concerns. Different range values add precision with old corroded and dirty sensors.

 

[Acesneights1]

I like this. Perhaps Kojo would chime in on the possiblity of modifing a PCM. Also I'd like more detail on making the cruise work off the existing PCM via a vacuum operated control.

 

[bobbiemartin]

Think of how the APP sensor would fail - drop outs and erratic readings including shorted or partially shorted wires. Thus you need two sensors to verify the APP position and prevent one failure for giving a false WOT reading for example. No way to failure check just one sensor for all possible failure conditions. Run a bypass was the least of their concerns. Different range values add precision with old corroded and dirty sensors.

I guess its hard to say why they did it. Seems like they could have got the same redundancy with three even scales. In any event, it pretty well eliminates using the PCM with a single APP input.

 

[bobbiemartin]

Also I'd like more detail on making the cruise work off the existing PCM via a vacuum operated control.

That is not exactly how it works. You don't use the PCM for the cruise and its not vacuum, its electronic. You would need a factory (or aftermarket) cruise stalk if you don't have cruise now.

You use a Delphi or AC Delco cruise box, like this one. Self contained, all electric, no vacuum required. Junkyards are full of them.

Wouldn't it be nice if all this info was available in one place - maybe in a book? It could tell you everything you needed for a conversion, where to get it and how to hook it all up.
:hmmm:

 

[buddy]

I guess I could test my theory that it will work fine with one TPS input. I could disable everything mentioned and just jumper the wires from APP1 to the pedal. I give it a try this weekend maybe.

 

[Acesneights1]

I realize factory Cruise is electronic but could it be wired to the vac control used on earlier non elec IPs like the one on my 90 burb. I have spares of those.