Has your AC quit also?
What year is your truck?
The PCM doesn't turn on the A/C, tach, and other instrumentation until it receives the signal from the engine speed sensor on the front of the motor (engine running).
I had this problem before and it was a bad ground to the PCM. I spliced in a proper ground wire at the PCM and never had the problem again.
For others, it has been a bad engine speed sensor (mounted on harmonic balancer or front of engine) or wiring problems.
The first place to check is the wiring to the speed sensor. You will have three wires. One is a +5 volt source wire. One wire is a ground, and the other is the signal wire that pulses with engine RPM. Make sure you have a good 5 volt signal and a good ground first. That will most likely lead you to your problem.
-Chris