I was testing my crank sensor signal and I saved a couple of traces. I figured I would post a snapshot. It's pretty boring to look at, but it shows what the crank sensor signal looks like. I didn't have an additional probe, if I did I would have gotten a trace of the CAM and crank signals relative to each other. Eventually I will do that, I'll get a start profile and then an idle profile. Anyway, I hope this helps someone.
Unfiltered Crank Sensor Signal Profile at Idle
- Thread starter MCH86GN
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Me too. At the end of the day, it's just a square wave. I have a function generator, I could reproduce this signal pretty easily and bypass the actual crank sensor signal and probably start the car.
Too bad Caspers doesn't have breakout harness, so these signals could be easily accessible and you would not have to probe the actual wire. I had to shave a little bit of the coating off to physically tap the signal, with the probes I have. A breakout harness would be nice, because you could hook up an o-scope to whatever signals you wanted and monitor and acquire data on them. An o-scope is a more practical and cheaper way to get traces like this. This required a Vector CANcase, it has a license on the hardware so I can use Vector's software apps., and an NI DAQ device and vector's CANape software app. to get this trace. The NI DAQ device comes with free data acquisition software, if you buy the hardware. The average person probably doesn't have access to this type of equipment and neither would most shops. A 4 channel input O-scope is not too expensive and if there was a breakout harness available it might help speed and diagnose issues a little quicker. Again the average person might not be able to use this, but I'm sure someone who works on these cars for a living could.
Caspers tooled up for a mating connector for the 3 way Metripack connector, so a breakout would be a simple chore.
http://www.caspersmfg.com/metripack-150-2-3-way-mate/
http://www.caspersmfg.com/metripack-150-2-3-way-mate/
I guess I should have been specific, I meant a breakout for the ignition module. So you could view as many signals as your data acquisition device would allow. Like have the crank, CAM, bypass, etc. all on the same trace. I have a bad ignition module, I'm going to remove the connector and then order the harness connector and modify so I can break out all the signals and connect them to banana jacks. I'll have one of the techs at my work do it for me.
Once I complete it I will post a picture.
Once I complete it I will post a picture.
RmvBfrFlght
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MCH86GN: the break out of the ICM connector is a good idea. I'm planning on doing the same (some day). The signals will get LEDs on them so that 'on the road' troubleshooting is easier. Same with the power signals, the 2 in, and the +10 volts out for the crank & cam sensors.
Can use Zerner diodes in series with the LED/resistor to only conduct if the voltage is over a certain level. Then use a small NPN (2N3904) to buffer the sensor & ECM signals as to not load them down.
John: glad you posted about the connectors. Not long ago I was looking for those ends with no luck. I found out that they aren't made by GM (Delphi), they only get used on a sensor by being molded in.
RemoveBeforeFlight
Can use Zerner diodes in series with the LED/resistor to only conduct if the voltage is over a certain level. Then use a small NPN (2N3904) to buffer the sensor & ECM signals as to not load them down.
John: glad you posted about the connectors. Not long ago I was looking for those ends with no luck. I found out that they aren't made by GM (Delphi), they only get used on a sensor by being molded in.
RemoveBeforeFlight
Actually we specialize in mating connectors which are patterned to the device. We design and produce several mates to industry connectors, supply "Plug-And-Play" solutions to the aftermarket - and some OEM applications. Actually if you call GM looking for mates, they will refer you to Caspers....
A few years ago I did a simple plug-in diagnostics piece that plugged into the CCCI connector - supplied Richard Clark with a few of them. Never did put it into production though. There were two LED's, one for the crank and one for the cam sensor. I think I also put in four other "Power Status" LED's for the volt signals.
Someday I'll revisit it. I think the reason I didn't produce it was because it would plug into the 84 cars, but the pinouts were all different.
A few years ago I did a simple plug-in diagnostics piece that plugged into the CCCI connector - supplied Richard Clark with a few of them. Never did put it into production though. There were two LED's, one for the crank and one for the cam sensor. I think I also put in four other "Power Status" LED's for the volt signals.
Someday I'll revisit it. I think the reason I didn't produce it was because it would plug into the 84 cars, but the pinouts were all different.
I will PM you. Very interested. If I would have had a connector like this a month ago, I would have been able to figure out what the issue was with my vehicle a lot quicker. It is possible for me to trace 8 signals with my laptop and data acquisition HW/SW.
Well you just upped the ante, now I'm thinking of doing something similar with LEDs. As far as the circuit you're describing, I would have to do some research on that. It sound relatively straight forward, but you're correct you can't interfere with the signal integrity and you need away to add the LEDs in such a manner that they are benign to signals.
What would be the purpose of the Zener diode? Reverse bias so you know the voltage is at the correct threshold to turn on the LED or for a short to battery? You would need one with a higher reverse breakdown voltage, to be safe 20V. I'm not so sure you would need one for a short to vbat. Here is a simple switching circuit, using a NPN transistor. Obviously you would want to limit the current as much as possible. Have just enough to drive the circuit.
RmvBfrFlght
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Here is something along the lines of what I was thinking:
The left circuit is for the two IGN+ voltages to the ICM. With the 8.2 V Zener the LED won't turn on unless the IGN+ voltage is over 8.2 volts. The Zener won't allow electrons to tunnel through until that voltage threshold is hit, then it starts to conduct. If leakage through the Zener causes the LED to glow, can add a resistor from the junction of the LED and Zener to ground.
Can use the same circuit for the +10 volts out from the ICM that powers the crank and cam sensors.
The right side circuit is an example for monitoring the cam and crank signals (using 2 separate circuits).
Note that with the LEDs being powered by the IGN+ voltage the LEDs will dim some as the engine is cranked over. And get brighter with a running engine. Can alleviate this by using a +5 volt regulator (LM7805), and powering the LEDs via 5 volts. The 1K current limiting resistor for the LED should be reduced to 220 - 270 ohms in this case.
Note that the whole thing is powered via the +IGN voltage going to the ICM.
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The left circuit is for the two IGN+ voltages to the ICM. With the 8.2 V Zener the LED won't turn on unless the IGN+ voltage is over 8.2 volts. The Zener won't allow electrons to tunnel through until that voltage threshold is hit, then it starts to conduct. If leakage through the Zener causes the LED to glow, can add a resistor from the junction of the LED and Zener to ground.
Can use the same circuit for the +10 volts out from the ICM that powers the crank and cam sensors.
The right side circuit is an example for monitoring the cam and crank signals (using 2 separate circuits).
Note that with the LEDs being powered by the IGN+ voltage the LEDs will dim some as the engine is cranked over. And get brighter with a running engine. Can alleviate this by using a +5 volt regulator (LM7805), and powering the LEDs via 5 volts. The 1K current limiting resistor for the LED should be reduced to 220 - 270 ohms in this case.
Note that the whole thing is powered via the +IGN voltage going to the ICM.
RemoveBeforeFlight
Ok. So you would use resistor in series with a Zener diode with an 8.2v breakdown voltage and LED for ignition indication. Then just duplicate this circuit twice if you want to monitor the 10v reference for the CAM and crank sensor.
The CAM and crank signals will be the switching source, base voltage, for the transistor, and the ignition or ignition to a 5v regulator will power the circuit/LED. Got it.
I have most, if not all these components, at work. If I give the techs a schematic the will built me whatever I want. At the end, I envision a box with labeled LEDs and banana jacks in case I need to access the signals.
Thanks for the circuit ideas. Did you do any simulation testing? I don't have the software on my machine, but some of the hardware engineers I work have Pspice or OrCAD to do design and simulation. Perhaps I could get them to simulate it for me, if you haven't.
Sorry if my post was confusing, the one with the circuit diagram I pasted in. I'm trying to work and post at the same time, not a good idea. I understand how electronic components work, I should, I have an EE degree. However, instead of going for hardware engineering I decided to do embedded software as a career. So I haven't done any circuit analysis/application/design, besides voltage dividers, since I was in college. For some reason, I got the programming bug.
RmvBfrFlght
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For testing the circuits the best bet would be to use a bread board and see how they act/work. Quick and easy real world testing. Can use the right hand circuit on the ECM to ICM signals: EST, RefHi, and Bypass. Can use a modified circuit to check Ref Lo, as it is a ground signal.
That way every signal to & from the ICM is checked.
RemoveBeforeFlight
That way every signal to & from the ICM is checked.
RemoveBeforeFlight
