EST Bypass

[DieselBob]

Trying to build a EST Bypass simulator.

What I'm trying to do is have the bypass signal switch the circuit..
I've tried using a <500 ohm and a >5000 ohm resistor test rig... still getting EST Error on an 808
It doesn't seem to make a difference what the RPM input is.

Been an ongoing thing that i dug out from under some other ongoings on the bench and had another go at it.
Not looking for the solution just a little help ....
The Bypass circuit doesn't make 5VDC best i"m getting is around 1.7VDC???
haven't tried another ECM yet didn't think about that till i sat down and started this

[VL400]

Not totally sure what your trying to do, but the bypass signal and EST line interact a bit. During low RPM (<400RPM) the bypass line tells the ignition module to control spark, the module also grounds the EST line. The ECU uses a feedback signal on the EST output (internal to the ECU) to check that although its commanding EST signals its grounded with nothing going to the ignition module. Its this logic that the ECU uses to set the Bypass or EST open/short malfunctions.

The bypass signal should go high (5v) above 400 RPM. But will need a pull down resistor, 10k will be ok.

[DieselBob]

Learning...
Trying to make a circuit that sims the DFI switching from bypass to EST.
So when the ECM sends the signal for the switch from bypass to EST the engine sim I've got stops the DTC from going active.
Started with a transistor and then when that didn't work tried a 4066 IC.

The bypass line has been left - not tied with a pull down
Using approx 220 ohm for under 400 RPM and a 10K pot on for >400 RPM on the EST line.
All the info has come from either the VN engine manual or the 1989 patent application for DIS.

So far I've got the previous voltages and a duty cycle of approx 50% and varying frequency's
RPM input upto max doesn't seem to be an influence.
Under 400 it won't log the error even with both line loose......
Worked late tonight so I'll try the pull down and a different ECM tomorrow

[vn5000]

You could buy a camira ign module and use that.Thats what i use for bench testing.

[DieselBob]

Its more of a what is possible with a few bits from jaycar and the bits in a tub in the shed....
I've got a couple of V6 Ignition modules so I'll make a harness when time permits, hook up and see whats going on.

[vn5000]

There was a post somewhere with scope pictures showing the waveforms of both est and bypass control wires in module mode and est mode.

[DieselBob]

After a lot of head scratching and web looking finally got it working 5 minutes ago

[VL400]

Nice work

[DieselBob]

Heres a schematic that will stop the EST/Bypass error on a bench rig.....
It's possible to rearrange the components, and i haven't played with the resistor values
they came from various sources but these work on the setup I've got....
hope this helps somebody gave me a few hours of fun getting it working

Bob

EST_Bypass Circuit.pdf

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