Gen 2 PCM to gen 3 PCM differences?

[fireguy12117]

What are the major differences between a gen 2 explorer PCM and a gen 3 ranger PCM for the same engine?

Really long story short, i swapped my reman'ed gen3 PCM for a junk yard gen2 explorer PCM and got the 93 to finally run like a normal truck- almost.

what steered me to do it was changing out 3 different MAF's and getting the same DTC 159. after extensive checking of wires and harnesses i swapped the PCM's and now the truck throws a 22 DTC and has detonation when accelerating onto a highway, or other high load/WOT conditions.

According to one source a 22 DTC is a MAP out of range (not sure on that accuracy of that), but id like to narrow down some differences or just get some feedback on anyones knowledge or opionions about what ive done in swapping an explorer PCM for a ranger PCM.

 

[fireguy12117]

according to my own research...well, opening a manual and actually looking really...i did discover that according to a chiltons book a 91 ranger has a MAP, a 91 exploder has a BAP, so it makes sense about the DTC 22 i am getting, but i wonder does anyone know if they calibrate these things down to vehicle specific weights and such?

anyone know exactly what a BAP sensor is? looks like its connected to the two same pins as the MAP on a rangers PCM.

 

[MAKG]

Umm, a 91 Ranger has a MAP only if it has a 2.9L in it. If it has a 4.0L, it has a MAF.

A 2.9L PCM should not be expected to run well (or at all) with a 4.0L. A same-year 4.0L PCM will probably run well, and will certainly run well if it has the same calibration code as the original. A different-year 4.0L PCM may have different equipment (such as EGR).

 

[fireguy12117]

The PCM from the junk yard that is running the ranger right now came from an explorer.

It was most definatly a 4.0 explorer, and it most definatly has a DTC 22 coming out of the PCM as it resides in the ranger.

I suppose the chiltons could be incorrect, but it does show both a MAF and a MAP on the same wiring diagram for a 91 ranger, and a MAF/BAP together on the 91 explorer diagram.

in any case, this all went through before me being aware of there being such important differences between PCM's.

 

[MAKG]

The difference between a MAP and a BAP is only where the air line goes. If it's to the intake manifold, it's a MAP. If it's to the outside (or ahead of the throttle plate), it's a BAP. The sensor itself is exactly the same.

I believe early 4.0Ls had BAPs (not MAPs) as a redundancy.

 

[rickcdewitt]

does your ploder have BAP micheal? mine doesn't. fireguy are both trucks non-egr?

 

[fireguy12117]

pretty sure. i know mine is a non-egr ranger 4.0. im pretty sure i grabbed a non-egr sploder pcm. as many trucks as i looked at the day i got it, i'm pretty sure i saw egr equiped RBV's and so it would have raised a flag when i looked under the hood first- which i did on all trucks- before going for the PCM. if anything, the only code present so far is the 22 for map. no EGR or DP sensor faults have apeared.

it runs fantastic i would say compared to what i had been dealing with, but i took for about 10 miles city highway driving tonight and she pinged rattled and detonated, so this is definatly an issue of getting the right PCM for the right truck, but seems to pretty well confirm i had a bad PCM shortly after swapping motors.

 

[Ranger44]

What exact year did you get the Explorer PCM from?

91, 92' only had one O2 sensor, in 93 they added a one and ran them off each manifold.

EGR didn't appear until 94' on non-cali Rangers.

IIRC, There is also a difference in the injector styles used between the years. Not sure if this would cause a problem.

Your best bet is to find a 93' non-cali 4.0 auto ECM either from an explorer or Ranger.

I CAN get one for you. I'm actually going to snag the engine out of a wrecked 93' Ranger with an auto tranny. I'm going to run a MT, and already have the proper "ANY 1" computer.

 

[fireguy12117]

Ranger44- sent a pm...

i read on here a similar statment, that they went from 14# to 19# injectors or vice-versa around that time. i really cant say if it was a 91 or 92, i just know it was a gen2 body style explorer. i couldnt find ANY gen 3 rangers with 4.0's at this particular yard.

wasnt sure when EGR came into its own, so thats good to know.

i guess what i am really curious to know is how exactly these things are set up. do they actually have a data table stored that says 'this is a ranger, so it weight is X lbs, and needs XYZ added in to its fuel trims", or how even it does its adaptive calculations from baselines given by the engineers...i at least figured out that the PCM actual does shifting signals, so thats a no brainer for MT vs. AT, but all the rest feels like a black box mystery.

 

[Ranger44]

91-94 Explorers are the same body style.

Well, the injectors went from a "needle" pintle to a disc pintle type injector.

Not sure on the flow rate.

 

[UrbanRedneckKid]

sounds to me like you put a sequential efi ecu to a batch fire engine.
check the injector harness, if it has only 3 wires (2powers,1ground) then it's setup for the batch fire system. fires 3 injectors at a time.
your ecu being 95÷ (also 94s w/cali emis) is setup for sequential efi witch fires each injector separately, and utilizes a 7 wire injector harness(6powers1ground)

before you go any further just verify you didn't combine these two systems. i also wouldn't even drive the truck till it's fixed, won't as easy to fix as swapping an ecu, when that ping blows a hole in your piston....

 

[fireguy12117]

the truck i have is batch. the explorer that the PCM came out of is undertermined- i didnt look at that before grabbing the PCM. learning things as i go here...

could a SFI PCM run a batch fired engine? if it can, i'll be parking it till i get the right PCM.

 

[UrbanRedneckKid]

yeah it'll run, like crap, but runs it.
i found all this out when i put a 93 engine in my 94 cali emissions truck. my sequential ecu ran the 93 batch engine. and mine ran the same you say yours does.

 

[fireguy12117]

well poo...

i have the truck at work and i have to drive home, so i'll just take it easy. if i stay off it, it doesnt detonate...what a learning curve! thanks a lot though for pointing that out- and everyone elses input too!