I was driving my 2005 GMC Envoy Denali and it lost total power and now won't start?

[Brandon]

For the past couple weeks my fuel gauge has not been working. I would fill the vehicle up with gas, the gauge would read full and then go right back down to empty. It does this non stop while driving, it will go up to full then back down to empty. Now a light is popping up in the vehichle to tighten my fuel cap, but it's on and tight.

Also, my speedometer has not been working. Sometimes I'll be driving and the speedometer will read 80mph when I'm actually going 45mph. Just two days ago Saturday, Dec. 25 my speedometer read 105mph and I was going 70mph.

And now just today, I was driving down the highway, and the envoy denali lost power, and it will not start up now.

 

[d in ny]

sounds like the speed sensor is gone or the crakshaft sensor
Check the fuel pump pressure also
It won t run unless the pressure is right up there

 

[Majordiezel]

Crank?

Sounds like a faulty crank sensor for the no start problems...
if the pcm is not reading any crank it will not send any fuel to the motor, it could also be linked with the speedo probs as well. the other day when i went to hook up the scan tool to scan for codes on my 02 envoy xl i wasnt getting any response from the computer and it turned out it was a blown cigerette lighter fuse. the obd power supply is ran through the cigerette lighter.
Good Luck with it.
Keep us informed.

 

[woodyoutwo]

same problem recently fixed.

Hello, I am new to this GMC Forum. I have used it many times before and im many cases it has helped with my problems. I recently just had a problem with my envoy that seems the same as yours. Last week I was driving along and out of nowhere my truck stoped running. When I turned the key nothing happened, no clicks, noises, the lights didnt dim, no starter, nothing. When I stopped I checked my battery cables, gas and fuses. Every thing there seemed fine there, so I towed it back to my house. After further review of my engine fuse block I noticed that the PCM1 fuse(10?) was blown. As soon as I put a new fuse in it blew instantly. My brother is a GM mechanic so he plugged in a scantool and got a no communication error and no codes. We then disconected each wire cluser from my engine control module one at a time and tried to start the vehicle. The middle wire cluster when detached from the PCM would not blow the fuse. This got us to think that it was the PCM that was shorted. I replaced the PCM, to no avail. Still the same problem. Upon reviewing wiring diagrams we pulled the fuel pump relay because it is connected to that PCM fuse. After that the fuse did not blow, and the engine turned over. This was a very satisfying moment in this adventure. So then we got to looking for shorted wires. I had my fuel pump replaced 2 years ago and we figured that we would start there. Since we couldnt get to the fuel pump without dropping the tank this was almost imposible. However, since the fuel pump was recently replaced there was a wire connection from the original wiring to the new fuel pump wires on the drivers side. When we disconnected this harness there was obvious corrosion within the connection likely due to moisture. We cut the harness out and spiced the wires back together and she started right up! AND, my fuel gauge hasnt worked for a year and a half and now that works too! So i figured that I would share this with everyone because it was a very interesting situation. Im sure if I would have brought it to a shop they would have changed my fuel pump. So in total, it cost me $80 for the PCM which im trying to sell back and $6 for the wire connectors. Woodyoutwo. 3/25/11Read more at http://gmcowners.com/gmc-forum/newthread.php?do=postthread&f=6&kcplink=1