I have a 95 BLazer, 4.3 , 4x4 2dr. The check engine light cam on the other day so I borrow a scanner to check the codes. Same scanner used by the auto parts stores, actron. Pluggged it in and keep getting an error that it is not connected to vehicle. Ignition is at On position. I have had this scanner hooked to the truck previously. Checked it on my 2000 Jimmy and it worked fine. Anything I can check to see if the plug in the truck is ok? Which terminals to check and what to check for?

Now thought I would drive to the parts store and it will not start. Cranks but does not catch. I do not hear the fuel pump run when the key is ON. Ready to get a pressure gauge to check the pressure. Also where is the fuse located for the fuel pump?

Thanks for your help!

 

Not all scanners are created equal and neither are all '95 Blazers. There were three different ECU/PCM configurations for '95. The very early '95s were straight up OBD1 just like the '94s. After that, there was the partial application of OBD2 requirements commonly referred to as OBD1.5 (has the OBD2 data link connector under the dash). And lastly, there were the true OBD2 versions. If your truck is the OBD1.5 variety, then you need a scan tool that explicitly calls out being able to work with 95 model year GM vehicles.

But first, check and make sure that you have +12V power to pin 16. It is powered through the AUX PWR fuse (#7 - 25A) in the instrument panel fuse box.

As far as the fuel pump is concerned, the pump is powered through the fuel pump relay located on the firewall. The relay gets it's +12V constant voltage from the ECM/BATT fuse (#9 - 20A) in the I/P fuse box. The relay is triggered by the PCM. There is a fuel pump prime connector located under the hood. It will be a red wire with a black or brown plastic connector on the end. You can manually power the pump with a fused jumper wire over to the battery positive post.

 

Thanks for the reply. My understanding this is a late production 95 and is the OBD2 version as I had used this same scanner previously. I will check for 12 V on pin 16 and check the fuse again.

I will check the #9 fuse again and try to run the pump with a fused jumper.

 

A quick way to tell which ECU/PCM you have is to determine it's location. If it's not under the hood on the passenger inner fender, then it's not fully OBD2.

If you know someone with a fuel pressure gauge, I would test the pressure & leak down rate. The CPI engines are notorious for failing fuel pressure regulators, bad internal lines, fuel pump problems, poppet nozzle issues, and the occasional injector harness malfunction inside the engine that can all cause no starts.

 

Thanks again for the info. The diagnostic plug is located under the dash on the driver side. The ECM is located on the passenger side on the fender.

There was a new fuel pump installed about 4 years ago on this truck. Headed out to the auto parts store now to get some wire and a fuse holder to check the pump and get a pressure gauge.

 

SwartLLk, thanks for the help. Found #7 fuse blown. Replaced that an the scanner worked fine. I could not find the Fuel pump wire. The fuel pump relays on this truck are in the glove box, from what I can determine from the service manual/ DVD I have. On the firewall are 3 other relays, I have not determined what they are for, still searching. I did replace the #9 fuse although it did not look to be blown.
i am doing this fro a friend to help save her some money but she needed the car so she had the garage come and get. It is now a matter of learning for me.

 

You are correct on the location for the OBD2 '95s. It is the center relay in the glove box. The fuel pump prime connector should still be under the hood somewhere. The schematics I have still show it even on the OBD2 models.

 

Interesting you say fuel pump relay is the center relay the glove box. I saw only 2 and figured it would be the relay on the left. There is a space for another relay to the right of the relays. I will continue to search for the fuel pump wire. This is now more for information for myself.