1991 Ranger PCM

[oolbreeze]

Hello
I have a bad PCM on my 91 ranger Vulcan 3.0 I have a 92 ranger with the same motor can I just switch them out or do they have to be programmed?

 

[RonD]

Welcome to TRS

Computers(PCMs) rarely fail, not never, just rarely

Pre-1995 Rangers use the EEC-IV 60-pin computers, which are more compatible between years.
What needs to match are:
Transmissions, manual and automatics used different software
EGR or no EGR

Other than that the 3.0l Rangers were pretty much the same until 1995

Yes, swapping '92 3.0l computer with the '91 3.0l computer should be plug and play.

Make sure to unhook the battery first, computers do not like power surges

 

[adsm08]

Add to all that, the EEC-IV computers can't be programmed.

 

[oolbreeze]

Right on guys . the codes are for the h20s the wide open throttle the brake on and off and master sensor but the keep alive memory wire failed test code made me think bad PCM. those are behind left side panel right? anyway the donor truck had a rebuild so I scored on parts with that and got a working transmission plus one to rebuild so I grabbed on the sensors as well. thanks again

 

[Tedybear]

Right on guys . the codes are for the h20s the wide open throttle the brake on and off and master sensor but the keep alive memory wire failed test code made me think bad PCM. those are behind left side panel right? anyway the donor truck had a rebuild so I scored on parts with that and got a working transmission plus one to rebuild so I grabbed on the sensors as well. thanks again

With several sensor inputs failing, I'd start by checking reference voltages and grounds. Sure it 'could' be a failed voltage regulator within the ECU/PCU. But these EEC-4 computers are actually pretty stout.

S-

 

[RonD]

If you post the code numbers it would be better.
There are several codes that are "test" codes, that means when you put computer into "communications mode" with jumper wire it expect you to open and close the throttle("goose test"), put your foot on and off the brake("BOO test") and other driver inputs, then it gives you the codes, if you don't do these tests then you get codes that the tests failed, so not "problem codes" just you didn't do the test codes,

O2 sensor codes can just be blown fuse for the O2 heater

 

[oolbreeze]

ok so the pcm had a broken pin so that was an issue the 92 pcm uses 3 digit instead of 2 digit codes and did not rev up the motor or show cylinder count gave me mass airflow low volts code with the other it was h2os low volts and gave me the 998 operating in failure mode. it runs smooth then just dies. I think these readings are off because transmission is fine tthe motor did not stutter or shake and was driving it the other day. do I need to drive it and let the new pcm get some miles on it?

 

[oolbreeze]

I mentioned transmission becaus I got I got a shift solenoid code when testin with motor off

 

[adsm08]

It may not idle real well (or at all) when the computer is first installed. I had to put a reman computer in my 87 around the 175K mark and it would start and die at first. I had to hold the throttle open and run it at about 2K RPM for a few minutes until the computer started learning.

 

[RonD]

998 (R) Did not pass Key On Engine Off test yet (Get 111 in KOEO first)


Have a look here for Ranger 3 digit codes: http://www.therangerstation.com/tech_library/3digitcodes.shtml

 

[oolbreeze]

So it idles fine for a few minutes also rechecked codes they are for no 02 sensor found that's because it has no 02 sensor at the moment well may be plug in the motor but not exhaust. this truck had serious issues when it was given to me things like JB welding the rear brake lines into the drums.

 

[oolbreeze]

ok guys I got all transmission solenoids reading bad the mas airflow reading bad and a 998 from the alternate pcm but after it warms up it runs strong and not to rich cause cant smell it. should I just ride with it?