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| GM LSx ECU ign output cct |
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| Circlotron:
Hi. What I am looking for is a partial schematic of a GM LS and newer ECU that shows the circuitry inside the ECU that drives the ignition coils. Specifically the little transistor and maybe collector pullup resistor and whatever else that gives the 0-5V output signal to the wiring loom that goes off to the ignition coils. I want to build an ECU simulator that gives the exact output that a real ECU would, as far as voltage levels and drive capability is concerned. Just simply using a sig gen is not what I want. |
| floobydust:
You'd have to narrow down the model of GM ECU and mated ignition coil modules. ECU ignition driver outputs are generally push-pull 5V current-limited to 20mA, with protection so a short to +12V will not backfeed and raise the ECU 5V rail, destroying it. The ign module typically has a smart coil-driver IC and IGBT inside. Some models of ECU and coil, the ignition coil module can (over the 5V trigger wire) send back diagnostic info to the ECU, such as current-limit target reached, over-dwell timeout. The ECU can also look for its (trigger) output shorted to GND or shorted to +12V battery, or open load. So the trigger line is not only a digital output but also can have switched current-sinks (by the coil module) on it, for diagnostics. If you want to fully test ignition coil modules, it's not just the spark but also the diagnostic signals to consider. |
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