So new here and have a question for the experienced!
Here it is, it is a 1995 2500 truck and it is a 6.5 turbo diesel, it has no glow plug or fuel pump power but if I jump the fuel pump relay (provide power) the pump will work but have to jump the glow plugs to fire up then it runs great! Also my scan tool will not communicate with the ecu, all fuses good so was wondering this! Would the ecu fail to provide power to the pump, and glow plug controller and not communicate with a scan tool but still allow the truck to run like a top if I hot wire the fuel pump relay? I can see no other issues once its running.
Sorry, I don't do a lot of GM stuff but could sure use a bit of help with this

 

The OPS powers the LP on your truck when the engine is running,it is common fort the OPS to fail on the LP circuit but work fine for the oil pressure gauge.
Replace with AC Delco only and google "OPS relay mod" for long term reliability.

The CTS tells the ECM when to cycle the glows,you might have a poor ECM ground or a bad glow relay causing the problem-not sure.
Make sure that all 3 grounds at the rear passenger side stud behind the intake are clean and secure.
More diagnosis might be required for the glows?

What type of scan tool are you using to try and communicate with the ECM?

 

Thanks for the info, I did replace the oil pressure sender but it was not with an AC delco so could try replacing again but will also check the grounds as described. My scan tool is a launch X431, never had trouble getting into anything before so was concerned there may be some ecu issues and also tried a small hand held and it showed error in communicating.

 

You understand that a 95 is OBD1 correct?

The info I was able to find on your scan tool only shows OBDII functionality but there was very little to go on so perhaps it does do OBD1 as well?

Make sure the lighter fuse is intact also since all OBD1 scanners I have used require accessory power.

 

It seems there might be confusion, the obd connector is the new obd2 style and the old obd1 plug will not fit so assume I am on the right track, My launch system comes with connections and software for 86 to 2010 so have it covered but not getting direct link with the ecu. I only looked at the vehicle registration for the year as the door tag was missing, is it possible it is a 96? I will check the dash vin. It is an electronic drive by wire pump!

 

Electronic pump started in 94.

 

Well checked the dash vin and it says it is a 97? Not sure how a regi can show different than a serial # but there it is, so OBD2 for sure.
Did change the oil sender with AC Delco but still same issue.

 

Ok I would say that you for sure have an ECM issue or a ground issue along with a possible air intrusion issue in the fuel system.

Make certain that the 3 grounds at the passenger side rear intake area are secure and clean.

 

If you are a 97 vintage that is OBD-II, do you have a non comms U100 code, I had it happen to my burb where the ABS module had a fault and killed the engine to puter comms, try unplugging the plugs from the ABS module and see if your scanner regains comms via the diagnostic port, the purple wire in ABS is common to the puter purple comms linkup to engine>

For gnds look here : 6.5 grounds