The attack on OBD2 begins

Hi Wood Gassers,

When I was at the Logging Museum yesterday I had an interesting chat with an auto service tech about OBD2. I asked him if I could go into the ECM and lock it into open loop mode without it throwing a “check engine” light. His response was “Why bother? It runs open loop when it is cold anyway.” That got my wheels turning. If I put a dummy resistor in place of the air and water temperature sensors I can make the engine think it is in Alaska in a blizzard. That should make it completely disregard the O2 sensor inputs. The thermostat is mechanical so actual engine cooling shouldn’t be affected. The engine cooling fans may never come on but that can be handled with an aftermarket thermostat. This is going to be my primary plan for the Ranger.

If that fails and there is no obvious path forward I am thinking about doing something like a Kickstarter. If you guys buy hardware from me during a certain period for the event, I will take all the profits and get a professional tuning shop involved. I will share the results with the “investors” and any extra money will go towards Argos 2016. Thoughts?



I may have missed something, why are you trying to get open loop mode? All that does is limit the computer’s potential to fine-tune things. You want the timing adjustment to be as accurate as possible.

The OBD1 Dakotas have open / closed loop mode too. All I can say is we notice things do run better after they get warmed up good, and it seems to be computer related more than the gasifier.

Getting it professionally tuned may be more worthwhile, lots of aftermarket tuning options for Chevys (unlike the Dodge 4.7L that Wes was trying to tune).

What is throwing the codes when running woodgas anyways. Id look at why those code are being set and start there. Or take a very small drill bit and drill through the instrument cluster until you pop that bulb. Problem solved!!!

1 Like

A better method to get it to run in an open loop is to get it to throw an O2 code. Cut the output wire from the ECM to the CEL or wire it to a light you can relocate out of view.

Messing with the temp sensor may create some issues especially on warmer days.


From What I have read disconnecting the Check Engine bulb disables the engine. Relocating it might be an option.



Maybe I am getting ahead of myself. Everyone seems to fear OBD2 for some reason. I am guessing that because we take away the ECM’s ability to control the fuel/air ratio it is bound to throw an emissions code. If we run open loop the ECM will ignore the O2 sensors and try to use the mixture from its internal tables and not throw a code.

If you guys are like me you can’t get an inspection sticker with a Check Engine light on so there is a requirement to get the Check Engine light off.

Am I still off base?


HI MATT .I have pulled several check lights,all these computor cars are wired a little differnt, my neybers 1996 chevy 4/4 350 truck,when the cooling temp sensor goes bad it shorts the something and it wont even stay running other than standing still,go too drive and stalls,called his brother inlaw,that worked in a gm garoge after changeing everthing except the coolant temp sensor.unpluged the sensor and he was doing donuts in the yard. the results of unpluging the temp would on the truck,make it run rich on fuel,after we replaced the 5 minut job,coolant temp sensor next too the theristat on intake,it run fine. If you resistored the cooling sonsor wire back too the computor too resemble a hot motor,than it would run leaner when cold, NOT sure what you be trying too change, the timeing is the only thing i can think of that needs changeing between idle and driveing. PS back in the garodge i go third tranny in my truck i broke the first one trying too cram the motor and trans in when the chain broke it broke the tranny bell.second one i dont know,thought was good no 3rd or 4th gear,the next one worked for sure.

my 97 don’t through any o2 codes I had to unplug my maf sensor so I do get that code and a timing code I just reset plug in pass inspection and do it again. p.s the light isn’t going to stop anything.

1 Like

What about using MegaSquirt?

How about moving to a county that has no emission testing?


There is a wide load restriction on moving 35 acre farms. :grinning:


I have no problems with my obd2 (1996) dakota. However, its a older OBD2 and it has a dist ignition. No CEL’s.

Another thing you can do to try and keep it in open loop is add a cooler T-stat. They make them all the way down to like 145 degrees I think.

1 Like

Also, in most states with emissions the OBD-II port is connected to and and error/fault codes are read. Removing the bulb will fail you before the test even starts as it is supposed to come on momentarily when ignition is turned on. If the technician doesn’t see it, he stops right there and instructs you to take it in for service. You can’t just fudge it with a timer either because when their computer connects to your vehicle it will know the check engine flag is set regardless of bulb status. The CPU has to be happy or he won’t be able to pass.

Now, as a recovering Californian (worse than alcoholism I swear, SOOOO good to be home in MI) I can tell you how the folks out there navigate emissions testing. They actually have an emissions inspection motor! Yep, they put the stock stuff in once every two years, pass inspection and then put it back in a box/crate and re-install their usual gear. It’s a PITA but it gets you around all that fuss. Those fellas can swap a motor pretty fast too I might add!


For inspection can’t you go back to gas and clear the codes? I know the memory would show there had been a code but around here light out is good enough.

I’ve been trying to think of a way to keep the system in check while having an inoperative fuel pump. I am thinking about a by-pass circuit near the fuel pump that is activated with a flip of a switch. Any thoughts?


1 Like

the fuel pump isn’t the problem depending on what type of fuel set up you have at the intake there is where the code problems come from . map/maf lean rich but it don’t really matter reset the light plug sensors back in run some miles get a sticker go back to wood.

1 Like