Hi guys,

Very new here. '95 GMC S-15 Jimmy, just replaced a rear end with a used one and had to cut out a portion of the Y pipe on the exhaust to replace my tranny filter. Welded the Y pipe back on and now I have a check engine light come on. Threw on my OTC OBDll tester and it asks if my key is on, and states it's not communicating with my PCM? Thought I had a problem with my tester, so I brought it up to Advance Auto Parts and I threw on their OBDll tester and same result. I checked my ACC fuse and cigar lighter fuse and all the other fuses and they're fine. One question I have B4 I bring it to the dealership. It asked if it was GMC from Canada on the tester? May this be the problem, if I didn't click on GMC from Canada and it was built there?

HELP?

 

Hmm. That's odd. OBD2 standards are just that... standard. Its almost like it isn't getting power. Have you verified +12v power to pin 16 and ground on pin 4? If you do not have both of these, then the scan tool will not power up properly.

Here's the pin layout:


You also have to ensure that the pins are not loose in the connector. I have seen it where sometimes the wires will just shrink back into the connector, never really connecting to the pins on the scan tool causing all sorts of weird problems.

Circuit 1850 grounds through G201 which is located above the main harness underneith the driver's side dash. If you find that you do not have ground to the DLC pin 4, then you may have a ground distribution problem. But this is a main system ground and has several grounding locations throughout that splice pack consisting of G200, G201, and G207 all connecting into the same pack. G200 & G201 ground on lugs separated by ~1.5 inches in the same location. I am unsure of where G207 grounds.

Hope this helps!

 

Thanks Swartlkk,

I had to make an appointment at the dealership but I'll check through this ASAP. I did have the OBD11 power up, but it said it couldn't communicate? Everyone I talked to stated that if it were a ground issue, it wouldn't have powered up the tester?

 

Ok, I must have misunderstood... I thought you couldn't get the scantool to power up.

Well, one other thing to throw in on this... For some reason I read '96, but you have a '95 which is a bastardized OBD system. It is a mix of OBD1 & OBD2 commonly referred to as OBD1.5. These systems usually require a special reader to access the stored codes. Advanced should have known this as they have a reader for this red-headed stepchild of all OBD systems.