Turns over wont start
Security light lit on the dash ? You say new coil pack , but is there spark ? Are the injectors turning on ? (squirting fuel ) Is there 5volt reference voltage at the sensors that are suppose to have it ? A shorted sensor can bring down the reference circuit in the PCM causing a crank - no start .
The powertrain control module (PCM) can supply 5 volts or 12 volts to the various sensors or switches. This is done through pull-up resistors to the regulated power supplies within the control module. In some cases, even an ordinary shop voltmeter will not give an accurate reading because the resistance is too low. Therefore, a DMM with at least 10 megaohms input impedance is required in order to ensure accurate voltage readings.
The PCM controls the output circuits by controlling the ground or the power feed circuit through the transistors or a device called an output driver module.
The engine coolant temp. sensor , fuel tank pressure sensor , MAP sensor .EGR valve , A/C refrigerant pressure sensor . The TPS sensors an the APP - accelerator pedal position sensors etc.. Any one of these sensors being shorted internally will bring the 5volt ref. circuit down , shutting down the PCM . Find one of these sensors an test for 5volts on the ref. circuit . If less then 5volts disconnect each sensor till you see 5volts on your volt meter .Then replace that sensor.
Nov 09, 2015 |
2005 Chevrolet Malibu