Quote:
Originally Posted by hardtailer
Status update from DME in the car:
Engine starts with OK DME and ICV disconnected. Based on this observation and my understanding of wazzz's post with the Spice simulation, my test result shows that even without normal ICV signal present, the reset signal to pin 9 of 8051 still goes to low and the processor starts processing.
Hooked up NOK DME, reconnected ICV and noticed the following:
-Upon ignition on, but not cranking, the fuel pump starts running immediately
This is not correct, obviously. It should do so only after the crank starts turning or key is turned to crank/run starter motor.
-Upon ignition on, but not cranking T504, 1012 in the TO-3 package gets hot within seconds. After 15 seconds it's too hot to keep your finger on it.
-Upon ignition on, but not cranking pin 14 and 15 to the injectors are pulled to ground for the duration of ignition on.
-under above conditions the reset signal is no different from as bench tested earlier.
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ICV signal is still present. Even if you disconnect the ICV unit from the ECU, the ICV driving signal is still output by the MCU on pin 5 and correctly seen by the watchdog. Hence the RST signal is kept low on MCU pin 9 and that allows it to run normally. This is for the OK ECU.
Now for the NOK ECU, as stated by Ingo, you should really first address the absence of ICV driving signal on MCU pin 5, which is the indication that the 8051 MCU is not running. That's why the watchdog circuit (LM139 comparator) keeps sending it RST pulses to wake it up, to no avail.
You don't need to connect the ICV to the ECU for these checks, as the ICV driving signal monitored by the watchdog is upstream of it