# Drive Cycle time for Computer - 97 Hardbody



## Tide97Hardbody (Mar 23, 2011)

First time poster. Just got a 97 Hardbody that used to be my Grandpas ride. It only has 66K on it. The battery was bad and I had to replace it and get an emissions inspection. Even though I drove the Truck about 40 miles the computer still is not showing any status on any of the sensor. Do you know how long it takes for the computer to start providing status? On a GM I had it took about 30 miles. Also, anyone know were the computer is on this truck? :newbie:


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## smj999smj (Jan 1, 2006)

Computer is under the passenger seat. By "drive cycle" I assume you are talking about the SRT (system readiness test) status. There is no "time" for the test to complete, rather the ECM has to see a number of parameters met during a trip cycle.


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## Tide97Hardbody (Mar 23, 2011)

Thanks. Is there any way to know when the computer is reporting sensor status? You can only go to the inspection place so many times before they want to charge you again. Could I use a code reader at Autozone to check status?


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## jdg (Aug 27, 2009)

If you had a real time OBD scanner, you could monitor some status parameters, particularly Mode $01, PID $01, and this is just a basic parameter set listed below, not all inclusive, it's only the minimum that the OBD spec calls for.



> Mode 1 PID 01: A request for this PID returns 4 bytes of data. The first byte contains two pieces of information. Bit A7 (the seventh bit of byte A, the first byte) indicates whether or not the MIL (check engine light) is illuminated. Bits A0 through A6 represent the number of diagnostic trouble codes currently flagged in the ECU. The second, third, and fourth bytes give information about the availability and completeness of certain on-board tests:
> Test available Test complete
> Misfire B0 B4
> Fuel System B1 B5
> ...


Past that, most cheap trouble code scanners won't give you that sort of info. And it's erased after each start so you have to check it while running.


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## Tide97Hardbody (Mar 23, 2011)

I don't have a Check engine light coming on just trying to find out how long mile wise or time wise before the computer starts to report the sensor status. I live in one of those Texas counties that require emissions testing via a computer.


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## jdg (Aug 27, 2009)

Right...You don't have to have a CEL to get the sensor status, and there's a bunch of different things that have to happen to get ALL of the tests completed. It's not a definitive mile or time thing...just certain things have to happen in a certain order to be complete, and if you break that chain of events, it basically starts all over again.

Download your particular FSM and read thru the section dealing with the ECU. You might find a way to speed up the process a bit or at least find methods to hit all of those parameters that the computer wants anyways.

PITA type of stuff...and that's why I said most cheap trouble code scanners won't give you that sort of info. More expensive types will give you info on the fly, likely including the above information.


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