interesting windscreen

[Terry Kennedy]

well my HUD idea is out. The part is OBD2 compliant but does not work with CAN protocol so it does not work. Got to love car makers having a "standardized" OBDII interfaces and then making 20 different protocols because F-you, that's why.

The CAN bus isn't connected to the OBDII connecor on Brammo cars. The wires exist in the harness, but were cannibalized (at least on the early cars) for the Masterlube solenoid. I think later cars got a dedicated Masterlube wire, but the CAN bus still isn't connected to the OBDII connector, though it may be connected at the ECU end. Note that properly, a CAN bus needs some termination resistors, but it works (at least for me) without them.

[bolus]

what ever protocol it is using doesnt work with the HUD. it works fine in the other cars. the scan tools and aeroforce gauge work fine in the Atom. I figured it was because of CAN since I saw it listed as the OBD protocol for cobalts after 06. But after spending a while trying to understand OBD 2 it was quick to see that it is all an overly complicated mess

[Terry Kennedy]

what ever protocol it is using doesnt work with the HUD. it works fine in the other cars. the scan tools and aeroforce gauge work fine in the Atom. I figured it was because of CAN since I saw it listed as the OBD protocol for cobalts after 06. But after spending a while trying to understand OBD 2 it was quick to see that it is all an overly complicated mess

My point is that there is no CAN in the Atom's OBDII connector unless you wire it up yourself, so anything that expects to use CAN on that connector won't work. And if it says "This car says it's a Cobalt, I should use CAN" it won't get very far, but may give a misleading error message.

[bolus]

Ok, you got me thinking about it again and I went and tested it on the chevy HHR and it worked. So what would be the difference between the connector on the HHR and the Atom that would make it not pick up (it just blinks). The device is getting power. it lights up but then does not register anything. Is there a pin or wire that isnt hooked up on the Atom that is on the HHR? (im off to check the pin out on the GM DVD) my Autotap scanner pics up this information (RPM, temps, etc) just fine on the Atom.

[bolus]

Ok here is the connector. Hmmm, only 4 wires



HHR pinout is
1 - low speed GMLAN
4 - ground
5 - signal ground
6.- high speed GMLAN +
14 - high speed GMLAN -
16 - positive battery
(others not used)

Cobalt is the same except
2 - PCM Class 2 Serial Data (LSJ)

The atom has 4 pins.
2 ?
4 - ground
5 - signal ground.
16 - must be positive battery



So I assume then by what is missing, I need a low speed GMLAN or highspeed GMLAN. is that possible to still hook up?

I see pins 1 and 2 of the first ECU connector are high speed GMLAM + and -

[Terry Kennedy]

So I assume then by what is missing, I need a low speed GMLAN or highspeed GMLAN. is that possible to still hook up?

Right. That's what I said - the wires are missing in the connector. High speed GMLAN == CAN

Signal 2500 (normally tan/black) runs from PCM C1 pin 1 to OBDII pin 6
Signal 2501 (normally tan) runs from PCM C1 pin 2 to OBDII pin 14

Those wires may be tucked behind the dash (like the MIL wire was) if you don't have a Masterlube, or maybe on newer cars with dedicated Masterlube wiring. But check the PCM connector C1 (unplug it, slide the shell off, and see if the wires are connected).

Wiring diagram here/here and connector info here and here.

Note that in the interactive SI, clicking on the "DLC Schematics" on the engine controls schematic takes you to a page with different PCM pinouts for a different engine, though the OBDII connector pinning is the same. That's the second schematic linked above.

[bolus]

Thanks for you patience. I did not connect GMLAN to CAN in my head so that was my confusion

I dont have wires to pins 1-2 (top left of this pic) so that must be the problem. Do you have any suggestions for wiring them in? Im a little nervous about damaging this connector.

oh, you are a god! thanks

[Terry Kennedy]

Thanks for you patience. I did not connect GMLAN to CAN in my head so that was my confusion

I dont have wires to pins 1-2 (top left of this pic) so that must be the problem. Do you have any suggestions for wiring them in? Im a little nervous about damaging this connector.

I mooched a couple of pins from Brammo back in the day. Let me look in the garage and see if I have some extras. Otherwise, presumably the dealer has them. If they're anything like BMW, they only sell them with pigtails already attached.

oh, you are a god! thanks

[Terry Kennedy]

I mooched a couple of pins from Brammo back in the day. Let me look in the garage and see if I have some extras.

Sorry, I only have one spare.

I think they're 15356827, 32 cents each at mouser.com. Note that Mouser has an annoying mis-feature where it isn't possible to link to product directly. Just enter 15356827-L (L for loose piece, as opposed to reel) in the part number box. They also have the connector body, 15452125-B, in case you're worried about damaging the shell. For completeness, the pin for the OBDII connector shell should be 12129484-L.

[bolus]

Thanks, I got some ordered. HUD project back on schedule!