99 Mazda Protege lost Vref, wont Start

99 Protege was running a bit ruff. Found a bad intake manifold gasket and replaced it. It started running fine, but the next day starting hesitating then died. Hooked it up the diagnostics and there were no codes at all. So we reset the PCM. Still no codes. With no fire to 1 and 4 we replace both coils and the cam shaft and crank shaft sensors with no luck at all.

Next we broke out the book and check the circuits. Found the the Crank shaft getting 1.5v and cam shaft sensors getting 0v. Disc all other sensors and reset the PCM and still same problem. Did a ground and short check with no luck. The TPS, Fuel pump, injectors all check out ok. Bought a new PCM and still had same voltage problem. So we got another PCM and still same thing. The last thing I have done is jumper 5v to the cam/crank shaft sensors, reset the PCM but the PCM acts as is there is no voltage at all.

I have been on this one for 3 weeks now and I know I am missing something.

Has anyone ever had this problem before.


If the vehicle has no spark and no injector operation, the EGI Control unit (PCM) may have a low or zero voltage "VREF" signal to run the sensors. This voltage is created in the Control unit (PCM) and feeds several sensors. If the VREF voltage is lower than 5 volts, monitor it while disconnecting the sensors that "share" this output voltage. If any are shorted to ground they will lower the voltage to all the others in this circuit. A "grounded" VREF circuit will shut EGI control unit operation down and prevent the engine from starting. This trouble will not blow a fuse or set codes.
2muchbass said:
well............did you ever find out what was wrong?
My Mechanic which is my cousin gave up on it and said he just can't fix it. So his dad asked me to leave it with him. Says that the whole issue is caused by a bad wire in wiring harness. Because of it the 2 injectors won't fire. So he is trying to find the bad wire and fix it.

Will let ya'll know when he fixes it..