Hello everyone,

While I'm not an expert, I have some general knowledge of car repair from helping my friend with his projects. I have a Mazda 4000 that I've neglected for a while, but I've recently started fixing it up again. I've changed the GEM module (the one behind the AC/radio) to try and fix my issue with 4high and 4low not working. However, I'm still encountering some error codes that I need advice on how to remedy.

Additionally, my friend had removed a "loctronics" board that was under the dash, thinking that it was causing issues with the immobilizer not working. I'm not sure if this could be related to my current issues, but I wanted to mention it in case it helps.

Here are the codes that I'm currently seeing, along with what I've tried and what I think they mean:


Module | Code | Info | Status

__________________________________________________ __________________________________________________ ___

PATS | None | N/A | DONE

OBDII | P1506-c | IAC valve higher then expected | indicator

PCM | P1506 | IAC valve higher then expected | indicator

PCM | p1000 | OBD System readiness test Not complete | Cause ?? of above ??
I think I need to run a test manually or drive it more.

RCM | None | N/A | DONE

GEM | P1808 | Four wheel drive low circuit Falue |
check fuse #'s : 10 , 20 , 25 , 28 all at 7.5 amps. advise from - all have continuity
https://www.ranger-forums.com/genera...-codes-152892/


GEM | P1898 | Transmission Transfer case |

GEM | P1832 | Transmission transfer case 4WD Solenoid |

GEM | P1838 | Transmission transfer Case shift Motor cir fal|

GEM | P1891 | Transfer Case Contact Plate Ground Return |

GEM | P1867 | Transmission transfer case contact general fal|

GEM | B1352 | Ignition key in circut fault |

RAP | None | N/A | DONE

If anyone has any advice on how to fix these errors and get my car to pass smog, I would greatly appreciate it. I'm hoping to improve the car as much as I can with my limited knowledge and skills.

Thank you for your help.
Also i attached some pictures of the board that was taken out in case its useful.

Befor was taken out

After taken out

 

Welcome to the forum

1999 Ranger/Mazda 4x4 can only use another GEM from a 1999 Ranger/Mazda 4x4, 3.0l or 4.0l engine won't matter to GEM

P1000 just means Computer was unhooked from power so needs to retest emissions systems, no manual reset for this, it will clear on its own after a few days of driving once other codes are cleared

B1352 just means someone disconnected the "key left in ignition" chime, its the chime that sounds if you open drivers door with key in ignition, people often disconnect it by removing the one wire on the key cylinder
But in any case doesn't effect anything and shouldn't cause a fail for smog as its not an emissions issue, and won't turn on CEL(check engine light)

P1808, check fuse 3 in engine bay fuse box, 20amp

P1505 means idle was high
After engine is fully warmed up let it idle
Unplug the 2 wire connector on IAC Valve
Idle should drop to 600rpm or so, engine barely running, or engine may even stall, either is GOOD it means no vacuum leaks
If idle does not drop then you have a vacuum leak causing higher RPM and P1506 means computer can not lower RPMs using IAC Valve

The B codes shouldn't effect passing smog and shouldn't turn on the CEL, so focus on getting the "P" codes fixed



1995 thru 2000 Ranger 4x4 system does use the GEM module as the 4x4 controller, but there is also a Dual Relay box behind it, in the radio cavity
These relay boxes rarely fail but that's not never

Simple description of how electric 4x4 control works
The shift motor on the transfer case is a 12volt DC motor, same as the electric motor for power windows
It has two wires, if one wire is + and the other - then motor spins clockwise(window up) if you reverse the polarity so one wire is - and the other + then motor spins counter clockwise(window down)
And just like power window motors, transfer case motor has BOTH wires as -, grounded, when system is unused
You can test for that by unplugging transfer case motors 8 pin connector, and testing if the Yellow and Orange wires both show 0 ohms to ground, i.e. transfer case metal or frame metal

These two wires(yellow and orange) come from the dual Relay box behind GEM, one relay for each wire
When these 5 pin relays are OFF, it grounds its wire to shift motor
When GEM is "told" to shift transfer case it only needs to activate ONE relay, which disconnects that wires Ground and connects that wire to 12volts, so shift motor moves, clockwise or counter clockwise, depending on which relay was activated

GEM is connected by 2 wires to the Dash 4WD switch, inside the switch are 3 Resistors, each a different value
With key on the GEM sends the switch 5volts which passes thru one of the resistors, selected by switches position, i.e. 2WD, 4high, or 4low
On the other wire GEM gets back, 4v for 2WD selected, 3v for 4high, and 2v for 4low
These switches never fail, not rarely, never, lol, unless you hit them with a hammer

Key on, when you change switch position you should HEAR a relay click, from behind radio, its not quiet, its easy to hear
That means GEM got the "message" from switch and "tried" to move the shift motor
No relay "click" means switch issue, GEM issue or Dual Relay box issue

If you do HEAR a click then switch, GEM and Dual Relay box are most likely OK

Shift motor and its Position system, the other 5 wires on the 8 pin plug
Inside the shift motor housing is a Contact Wheel and 6 contact bars(only 5 are used)
The contact wheel has metal traces, as the shift motor turns the transfer cases shift rod, these traces connect and disconnect from the contact bars
These connections and disconnections "tell" the GEM module the position of the shift motor and transfer case shift rod
Pics of all this in this article: https://www.therangerstation.com/tec...e-shift-motor/

If the GEM activates a relay and does not "see" the contacts changing instantly it immediately STOPS(deactivates relay), and GEM should then start to Flash 4WD lights on dash
This would happen if Dual Relay box was bad as well, as motor wouldn't move so no contact changes

The below wiring diagram looks confusing but just break it down into its 3 parts
Yellow and Orange wires for Dual Relay box(shift control module)
2 wires for dash switch
5 wires for position contacts

Brown wire is for electric clutch inside transfer case, nothing to do with control, can't cause system to not work, and was dropped in 2001 and up Rangers/Mazdas

 

Thank you so much for your reply. I apologize for the delay in responding; I wanted to try some things to see if I could fix the issue. I unplugged the IAC wires, but there was no noticeable change in the RPM. I've replaced a few hoses that looked cracked or had gashes, but I still haven't had any success in getting the car to drop RPM.

I've purchased a propane torch to try and find the leak, but I'm having some trouble since the bottle instructions say not to use it upside down. I've also read that the IAC valve can get stuck, so if I can't find the leak, I'll try cleaning that out next.

Regarding the P1808 code, I've checked fuse 3, and it has continuity. I'll keep looking for that leak, but any additional advice would be greatly appreciated.