(Apologies for the disorganized post - these are just my thoughts as they came to me while considering the problem.)
If it was a security system problem, the light would stay on. It lights up temporarily to show you that the light is working. That is normal.
The OBD2 port is fused. Does your accessory outlet, (aka, the cigarette lighter jack) have power? They share a fuse. I typically just plug in my phone charger and see if the light comes on to check these.
The OBD2 port connects to the ECM through the harness, but power for the port does not, IIRC. I don't have the service manual with me.
When the needles cycle on the cluster, it's a self-check that the cluster is performing. It doesn't have to talk to anything else to do that.
Normally, I'd say all of this sounds like a bad ground, or an intermittent / faulty negative battery connection. Have you looked at the battery terminals (and matching harness connections)? If it has water damage - or even if it didn't - then I could see some corrosion forming around there. BUT, you say you've checked all of the grounds:
1. Negative battery terminal.
2. One on the frame about a foot away from the negative battery terminal. 10mm bolt. (as are all of these)
3. Front of the cylinder head
4. Starter. (This one would make starting slow or just not work at all, but wouldn't cause issue with the cluster or diagnostic port)
The "service air bag" message indicates either a real issue with the air bags, OR a communication issue. For the airbags, this would be the BCM. That could indicate a break in the harness (VERY unlikely), a loose connector on ECM, BCM or cluster, a bad BCM or a disconnected airbag. (The airbag sensor recall issue will trigger the airbag light, but not in my experience a "service airbag" message.)
I suspect that the message is actually coming from the BCM, though, which would indicate that it's (at least mostly) working. :/ Someone else may jump in and correct me here.
Just for clarity: did you clear the message and see if another one pops up on the DIC?
I'd disconnect the BCM harness and check for power and ground. (The service manual will have pinouts.)
There's a big-ass harness connector near and below the engine bay fuse box - about 4" on a side, with a gray cam-lock type retainer - that I'd also check out.
The ECM is on the driver's side in the engine bay, near the windshield washer tank and under the coolant reservoir. Remove and reconnect the 2 or 3 (depends on the year and I don't know the cutoff) Large connectors, check for water, etc., and reconnect them.
But, going back to the OBD2 issue:
If the fuse is good, and you don't have power at the OBD2 port - I'll give you the benefit of the doubt and assume you're checking the correct pins - then the ECM may be the issue. The ECM is what's on the other end of the harness from the OBD2 connector. HOWEVER, it should still have power, even if the ECM was disconnected. (Though, I haven't verified this recently, just working from memory from four years ago.) (It's also possible - pretty easy, actually - to accidentally push the connector pin receivers back into the connector, with a multimeter probe, so that they will touch the probe but not make a good connection with a scan tool connector.)
If this were my car, I'd start by tracking down the OBD2 issue as it has the fewest number of components involved. Check the ACC fuse - also, make sure that the cable bundle that goes into the bottom of the engine bay fuse box is REALLY connected (I spent a week tracking that one down after an engine swap), remove and reseat ALL fuses and relays, check for power at the cig lighter port.
Do the headlights work? Bright as they should be?
The factory service manual has some really great diagnostic procedures for this kind of thing.
Blue-ish 2006 2.4, Werks stage 1 turbo, Borla cat-back, DDM braces, Spec aluminum flywheel, Spec stage 2 clutch, Werks aluminum radiator, some gauges, RKSport hood, Morimoto FX-Rs, GReddy Profec, Norm's fenders
'07 GXP, RPM Stage 2, Solocatless downpipe, TCE Wilwood 6 piston front brakes, 4-piston rears , Stainless brake lines, slotted/drilled rotors, BC Racing BR coilovers, Performance Autowerks intercooler, DDMWorks CAI, charge pipes and braces
Last edited by raygun; 12-30-2018 at 03:57 PM.