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Have an 06 cobalt ss power on with key no crank, bypass clutch switch and jumped relay car starts and runs and drives. Turn off with key and try start with key no crank no click. Has new started and all fuses are good. Any ideas?
Knowing how it works is key , the ignition switch is a low voltage input to the BCM - body control module . When the BCM see's start input it sends a message over the serial data network to the PCM / ECM - engine computer . When the engine computer reads this message it will energize the crank relay sending B+ voltage to the S terminal on the starter solenoid ,there by cranking the engine . Taking to a qualified repair shop that has a factory or professional scan tool to read BCM DTC'S - diagnostic trouble codes is what you should do , before you cause more problems .
Moving the ignition switch to the START position signals the body control module (BCM) through discrete inputs from the ignition transducer that engine crank has been requested. The BCM verifies that theft is not active and sends a serial data message to the engine control module (ECM)/powertrain control module (PCM) requesting engine start. The ECM/PCM receives a 12-volt signal from the park/neutral position (PNP) switch or clutch pedal start switch notifying that it is safe to start the engine. There is a splice on this circuit in the fuse block-underhood that supplies power for the starter relay coil. The starter relay coil control circuit is then grounded by the ECM/PCM closing the switch in the starter relay suppling 12 volts to the S-terminal of the starter. Ground is supplied through the engine block.
on Feb 16, 2019
How can I fix high idle?
In theory once the desired idle speed is programmed into the management system, in the absence of such faults as air leaks, sticking idle air control valve and suchlike it should be impossible for the idle speed to be much different from the programmed value because the ECU should continue closing down the amount of air bypassing the throttle butterfly until the idle is around the correct value.
I think you need to go back to basics and double-check the work to ensure everything is as it should be. In the absence of mechanical faults and ignoring the possibility of electronic problems a high idle must be caused by too much air entering the engine, either because the idle air control valve is not closing properly or because the throttle butterfly is not closing fully.
It is worth noting air can enter the intake through leaky diaphragms, split vacuum hoses or faulty pcv systems. It is also worth checking the egr valve if fitted.
on Jan 24, 2016
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