PCM Fuel gauge questions.
Simple question regarding fuel gauge output on most GEN 3 PCMs.
The Fuel Level output pin I'm assuming is a PWM output that opens and closes the circuit to ground on that output pin. In other words the PCM's fuel gauge output is sinking current from the fuel gauge via grounding not sourcing current.
Most aftermarket fuel gauges are setup for the sending unit signal being between 0-90 ohms. If you're hooking up an after market fuel gauge you're relying on the series resistance of the fuel gauge winding's to limit current on to the ECU.
At 100% fuel gauge duty cycle (that is the fuel gauge output pin on the ECU is fully grounded) what is the maximum allowable current on this pin without damaging the PCM?
Has anyone else ever messed with driving non factory fuel gauges with a factory ECU? I know the difference in ohms is all tuneable by a the tables in the fuel system section but whats the actual hardware limits?
For safety should i just let the PCM PWM control an N-Channel MOSFET that does the actual switching?
