coastertrav

Trying to start my NB, but it doesn't have an RPM reading. Using a 96 CAS btw.

I have built it according to the Megamanual, and the FAQ, with EBC, fans, and idle mods, but have not added the tach output mod yet, but that shouldn't effect my lack of RPM signal. I have the CKP signal coming in to the shielded grey wire (rather the white wire in it) going to the standard pin in the MS, and the CMP coming into the blue/white wire on IAC1A. The Megatune shows all sensors but RPM, even while cranking.

Anything easy to test with a standard multimeter?

Here are some pictures of the top and bottom of the board.

akaryrye

iTrader: (5)

Cas is wired up correctly? Test it by hooking up a multimeter and spinning it by hand to make sure it triggers on and off. Reflash the firmware, check your trigger wheel settings. That resistor on js2 isnt touching any other leads i hope. Check for continuity between the ends of your circuit mods and verify the resistance.

Was the board tested with a stim prior to modifications?

coastertrav

I just have the megastim, not the Jim Stim.

I can check the cas though, give me a moment.

EDIT:

I have checked for continuity through my mods, and all seems to be fine.

coastertrav

Went outside and cranked the car with the multimeter inline with the CMP signal wire and the voltage jumped around when cranked. Obviously not terribly helpful, but I think that should mean that it is getting the signal.

coastertrav

Anyone?

I literally have no clue what to look at next.

Matt Cramer

Put a volt meter on JS8 and TSEL. Take the CAS off and rotate it by hand. The voltage at both these points should go from 0 to 5 volts and back again as you turn the CAS. Let me know what you find there.

coastertrav

Did that, and the voltage stayed right at 5.49volts.

Damn, so is that something in the board or the sensor?

Braineack

iTrader: (62)

Do you have d10 both jumped on the top of the board, and the diode installed on the underneath?


not related, just curious.

coastertrav

I have D10 installed on the board, just hard to see in the picture, and the diode on the underside is D8, nothing really jumpered over there.

coastertrav

Gay, I think I found the issue. Apparently I was sold a bum cas, because when spun by hand the only readings I get on the multimeter are completely stable on both the CMP and CKP outputs.

akaryrye

iTrader: (5)

if you are not getting switching from 0 - 5v at js8, then you might want to start tracing the signal back to the CAS. You said you measured resistance or something at the CAS, thats not really what you need to look for. Take it back off if you have put it back on and have the wiring harness plugged in to it and the key in the "on" position so it gets some power. I dont remember if its 3 or 4 wires or what, but I would assume there is a +5v input, possibly a dedicated ground, and an output wire or two which act as the ground wires. You want to hook the multimeter up to the output wire and spin the CAS by hand. If you see 0-5v switching on/off, you have a working CAS and you can move on. At that point, make sure the correct wires are connected to your megasquirt harness in the right spots. Just check it again, all of the problems ive ever had were because the wiring harness was built wrong.

Edit: well it looks like you found the problem, shouldnt be hard to find another one. Id sell you one if i had it. Post a WTB

Braineack

iTrader: (62)

d8 should be removed with the pwm idle valve mod.

coastertrav

Yeah, I had it uninstalled initially, but somewhere along the lines heard that it was needed (hence it being on the bottom).

Thanks for all your help guys, I'll let you know how it all goes when I get a new CAS.