simple curcuit request

[Toaster]

Id like to do the following to assist a friend in his auto repair buz.
A simple curcuit with a green and a red LED that works as follows:
The green LED lights while a "tach" signal is present and the red LED lights when its absent.
We found the problem with test light jigs but I wanted something more responsive.
I`d like the red LED to remain off even during normal coil off time but respond when the coil has missed a pulse.
Ideally, this lil doo-dad would connect within the passenger compartment, possibly to the diags connector. Any ideas?
The device can not be intrusive (cutting and slicing) nor effect the existing ignition in any manor. I would perfer a simple "clip in" of a generic affair that isn`t model specific or adaptor cable sets would suffice.
Remember, many vehicles have combination coil/cap configurations and outside connections are cumbersome.

Dork Vader-
Use adaquate force Luke! *crack* att`s my boy!

[DPunisher]

Hmmmm, not so simple a request. Have been an automotive tech for 16 years, last 10 as electrical/engine perf tech for local dealership. The easiest way to ck for a primary ign miss is with a simple test light hookup on the negative side of the coil assm, which sounds like what you have already done. If these tool salesman had found something like you describe, they would have sold me one already. Probes exist that can sense a low output on the secondary ign side and flash the LED's in the fashion described; however, not for the primary side. Tools also exist that connect into the dcl port in the vehicle to display a power balance for the engine. This unfortunately does not measure ign pulse but the actual miss caused by a missed ign firing. On OBD II vehicles with the dcl connector in pass compartment there is not a direct output for ign feed that can be used to directly ck for an ignition problem. All engine data is "secondhand" from pcm, ie. not directly measured from actual wire harness or engine sensors.

[Toaster]

I`m fairly close to making the curcuit but I have a shortfall.
I wanted the "red" LED to remain lit after a primary ignition pulse error. It simply "flashed" then went out. My next step is connecting a printer to "log" such activity.
True, a local conection would be tricky but tach sensors (CAM/Crank) data is available without undo difficulty.
I`d like the red LED to flash an equivelent number of times relavant to misses.
In this way, the engine had an "unfired" condition for a given lenth of run time.
Still, it doesn`t differentiate between a "module" or sensor error and a ECM mis-fire.
It would be neat to decypher between "where" the mis-fire occured.

[Charliey]

Well, i only know a bit about electronics, but to get the LED to stay on could you use a relay latch circut.

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-Charlie