This sucks. I'm away from all my diagnostic tools and my brain is not helping either. 1996 12 valve. Problem......I turned on my A/C and realized it isn't working. I then looked at my gauges and noticed that the volt meter reads discharge. When I start the truck, I have to depress the throttle pedal before it will start, it shouldn't do this.

I have no schematic or DVOM with me. All these inoperative items worked fine yesterday. I do have a test light and have checked all the fuses and have rotated some relays.

I find it hard to believe that all three things went out in one day.

Any ideas?

Thanks,
Don

 

if there is no RPM signal from the ENGINE SPEED SENSOR (similar to crank sensor). The PCM will never energize the ASD relay or send power to the generator, in turn all the components listed will not operate. On some later applications (1998.5 - 24 valve - ecm) the power for the alternator comes directly from the pcm to the alternator. The RPM input is needed to actuate the ASD or power for the field (+) of the alternator. Unlike the gas engine, the asd relay is not needed for the truck to run.

 

Thanks! You hit it right on the money.

 

Wow! Good post BigIron70!