• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Use of a "key" type diagnostic tool

M

MechanicallyInclined

New Member
Messages
13
Reaction score
0
Location
Canyons of Western Colorado
On the OBD-1 I have read "never put the jumper in or take it out with the key on".

I have a "key" type diagnostic tool to use instead of a jumper wire or metal paper clip.

I have yet to learn what is supposed to happen if the key is inserted into the data ports AFTER the engine is on or pulled out prior to shutting the engine off. What kind of damage can occur?

My second question is:

I have suspicions that my crankcase position sensor (CPS) could be faulty. If it was, I would get a code 19. But this code is not setting. I have been told that sometimes these codes do not show up.

As an experiment, could I insert the diagnostic key into the data port, turn on the engine, drive down the road a little ways and see if a code would start flashing on the SES light? OR while driving and the engine dies on me (as if the ignition switch was turned off), would a code then show up on the SES?

:confused: :confused: :confused:
 
MechanicallyInclined said:
On the OBD-1 I have read "never put the jumper in or take it out with the key on".

I have a "key" type diagnostic tool to use instead of a jumper wire or metal paper clip.

I have yet to learn what is supposed to happen if the key is inserted into the data ports AFTER the engine is on or pulled out prior to shutting the engine off. What kind of damage can occur?

My second question is:

I have suspicions that my crankcase position sensor (CPS) could be faulty. If it was, I would get a code 19. But this code is not setting. I have been told that sometimes these codes do not show up.

As an experiment, could I insert the diagnostic key into the data port, turn on the engine, drive down the road a little ways and see if a code would start flashing on the SES light? OR while driving and the engine dies on me (as if the ignition switch was turned off), would a code then show up on the SES?

:confused: :confused: :confused:
Click to expand...

Reading OBD1 codes with a jumper is reading the flashing SES light, code 12 should flash then each code that is stored after that. Reading the OBD1 flashing light takes some skill, The pause between codes is brief, erase all of the codes if you can and start over, reading the codes set after clearing.

Auto Zone or most parts stores will read your codes for you for free. Just because you don't have a code for a CP sensor doesn't mean the sensor is good it may be bad, it may be within specs, and possibly intermittent. The CP sensor makes a digital voltage signal that is sent to the PCM so that it can reference the crankshaft position sensor.
 
96GMC6.5L -- Oh, duh on my part. Yep, I meant crankshaft. I guess I've been dealing with vintage dirt bikes too long.

Slim Shady -- As a matter of fact, Autozone was the one who gave me the "key" for free. Handy little gadget!

But what damage can occur if I insert the key into the data ports with the ignition in the ON position? What damage can occur if the key is removed from the data ports if the ignition is in the ON position? :confused:

What about my experiment?:confused:

Oh, by the way it's good to know that Autozone or other parts stores will read the codes for free. My problem is that I live 50 miles from the nearest parts store and repair shops. Towing would cost me over $275.00 just the one way to town. You guessed it...I live in a rural area. It might take me all day to get to town driving my truck because of what it's doing. But that's different thread.:mad2:

I've also read that when the ignition is turned off that it is like a "soft reboot" to the system. There may be a problem, but the problem is not severe enough to cause a code to be stored and therefore the problem is erased until it happens again. I know a "hard boot" is when the negative battery cable is removed for a few minutes before being reconnected and all codes are erased.
 
Last edited:
Mostly it goes back to good electrical practice of never adding or remove load to an energized circuit, with key on the circuit is live, and if jumpered you would be reading the active test pulse turning on the lights, I've in haste done it I've yet to damage PCM as result of doing it "live" but risk is there so to play it safe you want to do with key off.

IIRC to clear codes OBD-I you disconnect the batts and codes clear after maybe 5 minutes or so no power to the PCM.
 
Thanks, Turbine Doc. What you said makes alot of sense. :iagree:

I certainly would not want to create more problems and have to replace more parts than necessary. It's confusing enough learning about the 6.5TD and trying to deciphyer what my current problem is than to add on to the dilemna. Like learning a new foreign language.
 
6.5s are easy compared to some of the conventions used in "modern" Diesels, sort of why many of us refuse to go to newer Diesels, much easier to work on/understand these, and significantly less expensive to work on them.

As I type this I'm sitting on break from AC traction motor locomotive Diesel class wanna talk about stuff that will twist your noggin around, AC voltage converted to DC, then back to AC via phase modules, controlling AC motors and DC charging circuits :mad2: brain cramps :eek:
 
You must log in or register to reply here.
Back
Top