GM OBD Readiness monitors - Damn you GM

sandlapper

Veteran Member
Oct 9, 2020
1,653
SE CSA
dunno if this'll help in Kali or for 01 vette LS --- this hack was widely bandied about until feds got wind of it and shut down any adverts. I did this w/ ubiquitous Ford 4.6L V8 modular. To defeat MIL lamp and bad cats.
I forget the fine details but it amounts to a shunt around of the O2 sensors. Sensors and empty cats stay in place but a resistor & diode is patched into the sensors' pigtails. It feeds a signal back to ECM that's within the reference range so ECM believes all is well --- when it's not. Car runs great. However, I'm Not in Kali, nor is it subject to any emissions testing/registry.
 

Javelin3o4

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Lifetime Gold Member
Apr 21, 2004
1,951
Concord, CA
Cali is 8 years for a any model that is less than 4 years old that started in 2019. I had a helluva time getting everything set on my 2000 Camaro. They tried to fail me at first cause the catalytic converter number was no longer on the "approved" list. Luckily I save all my maintenance/repair receipts, so I had to drive back home get the receipt from when I got the cat installed and show that. Its dumb, because the MFG of the cat no longer paid to have the part # on the approved list if you don't have receipt you have to go and get a new approved cat installed.
 

FS87LT

Veteran Member
Apr 3, 2010
104
DFW, TX
Had something similar on my 2005 LeSabre LTD. Battery got too low and had to jump it off, same as a "disconnect", it seems. Took it in for inspection and not all of the sensors were working. ONE can work in TX, but not two "not ready". Downloaded the driving cycle for reset. It included a section of 60mph to zero mph coast, without using the brakes, yikes! Where am I going to be able to do that without causing traffic issues? Found some low-use access roads to do that. Also an accel sequence at particular throttle settings, too. Ran it a couple of times and got the sensors on-board. Took it back to the dealership and got it retested for free, after paying for it the first time. Other people I know just "drove it home" and all was well for them.
 

Lars_2Gen

Veteran Member
Dec 29, 2017
797
Fullerton, CA
Just had this happen on my wife's Civic. Had the clutch replaced and took it to get a smog check two days later... the guy who did the clutch didn't tighten the battery terminals when he reassembled the car. Failed smog - O2 sensor not ready. Had my wife drive it for a week, And it passed fine. I know this doesn't help with your problem... but it's a joke that they don't actually test emissions any more. Who cares what the computer is doing if the tailpipe is clean!
 

danbrennan

Veteran Member
Lifetime Gold Member
Mar 13, 1999
4,965
Brighton, MI
That's old modula software - P59 or P01 controller? I can't think of anyone left ask about that. I knew some of the people that worked on that software set, but the ones I knew are all retired now.

If you look at the PIDs - real time data - is the relevant O2 sensor moving around as soon as the other one? If the heater truly is bad, on cold starts I would expect that sensor to be slower to start oscillating than the other sensor.
 

Lowend

Administrator. .a car, a man, a maraca.
Staff member
Lifetime Gold Member
Mar 25, 1999
16,854
San Jose, CA, USA
I just need to be patient... which is not a strong-suite for me. Since I work from home now, I don't drive a lot of miles. Gotta do more weekend cruises
 
Oct 9, 2017
30
I hope this helps .. i sniped the information off of shopkeypro
 

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Lowend

Administrator. .a car, a man, a maraca.
Staff member
Lifetime Gold Member
Mar 25, 1999
16,854
San Jose, CA, USA
I got the monitors to set. Even though the car had NO MIL, no codes, or pending codes.... one of the Oxygen sensors had gone bad. I replaced all 4, figuring they are all the same age. Heater readiness set within 3 minutes of the first fire-up.

Yep... I actually had a bad O2 sensor.
....Let the taunting begin
 
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danbrennan

Veteran Member
Lifetime Gold Member
Mar 13, 1999
4,965
Brighton, MI
Odd about no codes being set. Although as I recall we went across the board with OBD 2 only in 1995, so the software may have not been as robust to battery disconnects, ignition dropouts, etc. as it later became. Plus resources were being pulled away from that old Modula code in the late '90s and early '00s, after spinning Delphi off into a separate company(Delphi owned the rights to that particular version of Modula that they developed - GM Modula).

Anyway, glad you got it working.
 




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