Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
2003 gmc envoy 4.2 with key on no check engine light on dash and will not crank.Unplug the throttle connector (tac) turn key on check engine light now comes on and vehicle will now crank but not start.codes: u100 looking for some direction
If you have some sort of short to ground on he 5V reference to the TAC that could shut down the ECM. I would see what voltages you have at the TAC with it plugged in and unplugged. Likely to need a wiring diagram to see what you should have at the pins.
The vehicle should start without the TAC. You may want to see what your missing with it unplugged and treat it as a crank no start.
93Rubie wrote: The vehicle should start without the TAC. You may want to see what your missing with it unplugged and treat it as a crank no start.
Totally agree here! If there's any doubt about enough air getting into the engine during cranking, then you can try holding the throttle blade open during cranking. Or, pop the brake booster hose off.
Was the U1000 stored in the ECM? Do you have communication with other modules?
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