5 volt reference from PCM
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TECH Apprentice
Joined: Jun 2002
Posts: 319
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From: NH
5 volt reference from PCM I am using the 5 volt reference and ground from the PCM for the Fuel Pressure sensor to power my VATS box. (Because I needed 5 volts in to produce a 5 volts out 50 hz signal and because I am not using the fuel pressure for anything). I started the motor and it ran fine until I stabbed the throttle, it immediately died. In the process, I also lost all 5 volt power (EGR, Fuel, AC, etc.) I was able to restore the 5 volts by resetting the PCM codes (pulling fuses). I started the car again and let it learn the fuel map before stabbing the throttle and it has run good ever since. Anyone know when/what would cause the PCM to shutdown the 5 volt circuits? As for current codes, I was able to hook my father's shop's Snap-On scanner up using the 98 Pontiac vin (my engine is a 2000 Pontiac and this tool only goes up to 98). Suprisingly, I got some codes out of it. Mainly EVAP and EGR stuff. All of which is disconnected on my motor. I wasn't able to do any functional tests (bi-directional) because it said unable to communicate. Does the engine need to be running for this? If I can pull codes, I would think that I can communicate but that is not the case. I know the LS1 98 PCM's are different than the 2000 PCM's, but I would imagine that OBDII has standardized on the fault codes. Is this true? Also, I have no 02 sensors in right now, yet I see no codes for that. Why? Sorry for rambling. Any insight would be appreciated. I will be getting a proper scan tool shortly.
Joined: Nov 2001
Posts: 1,707
Likes: 33
From: Anderson, Indiana
Re: 5 volt reference from PCM There is really nothing that would shut off the 5 volt lines, unless you possibly grounded one of them. That would pull it to zero volts, but I don't know why it would stay "off". At least it came back up!
Although many of the OBD 2 fault codes are standardized, the serial data streams from different PCM's, engines, carlines, and manufacturers are still a lot different!! My Tech 2 would have simply said "Unable to communicate, recheck ignition switch and vehicle year". It would not have read ANY codes on your 2000 with 1998 entered as the year.
Most bi-directional tests run fun with the key on, engine off. Things like raising and lowering idle speed always work better with the engine running. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
Although many of the OBD 2 fault codes are standardized, the serial data streams from different PCM's, engines, carlines, and manufacturers are still a lot different!! My Tech 2 would have simply said "Unable to communicate, recheck ignition switch and vehicle year". It would not have read ANY codes on your 2000 with 1998 entered as the year.
Most bi-directional tests run fun with the key on, engine off. Things like raising and lowering idle speed always work better with the engine running. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />
__________________
91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
