mindvexed

Hello All,

I've been a long time lurker of this forum, and have always been able to figure out any problems using the search feature. However, I've finally come up with an issue that has me stumped which no other threads seem to address.

I'm having some trouble getting my 99 MN6 FRC to start, it cranks over but won't even pretend to fire.

I pulled it into my shop last week to change the oil, install a new multifunction switch (I was having blinker issues), and put in new intake gaskets (the old ones weren't looking too good when I put in a oil pressure sensor a while ago). Except on days of heavy snow or particularly bad roads (I'm in Fargo ND), I'd been daily driving it up to that point.

After doing my maintenance, I found that it would crank over but wouldn't start. I also found that my security light would occasionally flash and my steering column lock was giving a DIC display of either "service steering column" or "remove key wait 10 seconds". The car was also throwing a B2723 passkey code.

I cleared the code, and after a bit of troubleshooting, I found that during disassembly for the multifunction switch, I'd broken a wire on my column lock bypass unit. I repaired that and got rid of my column lock issues, but was still having trouble with the car not starting.

Since then I've done several other things that I hoped might fix the issue, including: checked fuel pressure, checked spark, removed airbridge/disconnected MAF, disabled VATS using HP Tuners, followed Bill Curlee's ignition switch contact cleaning procedure, checked BCM/Ignition/etc related fuses, disconnected/fully charged battery overnight, and tried to do the "30min" BCM relearn.

I'm sure I'm getting fuel because I can hear the injectors when cranking and my wideband starts sensing gas in the exhaust after prolonged cranking, I know there are no air restrictions, and I checked that I have spark.

After rechecking my codes this afternoon, I found a 1255 history code, but I didn't write down the initial letter, so I'm not sure if it's a C1255 (EBTCM/CEBCM internal malfunction) or a U1255 (generic loss communications / serial data line malfunction). I'm planning to take out and clean the BCM tomorrow in case some snow melted on it when the car warmed up in the shop. I'll also pull the code again, and this time I'll actually write the whole thing down.

If cleaning the BCM circuit boards doesn't fix the problem, I'm hoping to coerce an acquaintance into lending me a Tech II on Monday to do a system-wide scan.

I'd appreciate any suggestions for other things to check before I call in a favor for the Tech II.

Thanks.

Dave68

Have you ruled out a massive vacuum leak?

mindvexed

When the problem first arose I re-pulled and reinstalled my intake and double checked all connectors. I forgot to mention it, but I also replaced my MAP sensor after the no-start condition because the original one seemed somewhat fouled by oil and the pressure readings seemed off. I recently installed a catch can, but before that the car seemed to pull a lot of oil through the PCV system which is probably how the MAP got fouled.

I didn't ever recheck my map readings after the new sensor, so I'll definitely have to do that. Hopefully I just pinched a MAP wire somewhere. Thanks for the input.

Dave68

I wish I could be more helpful. Hopefully, the weekend crew will chime in.

RonSSNova

If you have fuel, and have spark, it should try to fire. What do the plugs look like?
How did you check spark?
There is a ground on the back of the drivers side head that can be rather easily broken when doing intake manifold work. Check that. I believe 2 wires go into the lug. It has tripped up more than a few folks.

Ron

mindvexed

Thanks for the suggestions Ron. Unfortunately I haven't had a chance to look at the car this weekend, and it looks like the weather's probably going to keep me from getting to the shop tonight as well.

To check spark I pulled a plug wire, put in a spare plug, and had a friend crank the car over. I didn't check the plugs themselves, but I replaced them a couple months ago and I assume they're not the primary issue since I drove the car into the shop.

I'd tried feeling for that engine ground after I reinstalled the intake, but had a bit of trouble wedging my hand in there. I'll have to recheck it and will probably take a look at some of the other ground terminals since these cars seem to have finicky ground issues.

After thinking about the spark and fuel statement you made, I got to thinking that I never checked that the throttle body is opening to allow air flow. If it's not opening it would explain the unusual MAP readings I was getting.

Thanks again for the input guys, I'll be sure to try your suggestions when I actually get to take a look at the car.

K-Spaz

I just started a similar thread last week. Mine is a 98, A4, and only when cold, it will sometimes crank without starting. Bill Curley gave me a procedure to try and suggested I stick the fuel gauge on, which I will do. Mine also is sitting waiting for me to get time and desire to deal with it. Mine seems to only happen below freezing though, and mine is indoors in a heated building. I have to sit it outside for a few hours to even see what's going on.

I will tell you though the only thing that makes mine fire up is if I throttle up a lot while cranking. That usually gets it to fire up. From there, the car idles fine, has no codes, and won't act a bit abnormal.

Last fall, a bottle of Techron seemed to help my starting considerably.

mindvexed

After borrowing and installing a buddy's BCM, using a Modus to go through all the control modules, bypassing the passkey system, and double checking every plug, wire, ground, and vacuum line, I finally figured out what my issue was: battery with a bad cell.

It was a 13 month old interstate, so I assumed it was fine. It provided around 12v when minimal power was being drawn, but apparently the voltage dipped during starting. I'm feeling pretty stupid right about now for not checking it first. But I figured I should post a follow up so next time someone else is searching the archives trying to figure out their issue, they'll see this thread and save themselves some time.

Thanks again to all who helped.