ECU Not Talking

thumper_svx · #1 03-02-2011, 02:46 PM

OK, first problem has come up. Dropped my car off this morning to have the state inspection done to get it legal on Missouri roads and have hit up against an issue. Basically, they failed it on the emissions test because the ECU contained no data from any of the sensors.

I am going to hook up my OBD2 scanner after work, but anyone any ideas what I could look for to figure out why it seems to be not talkative?

RojoRocket · #2 03-02-2011, 04:55 PM

Just curious about the actual problem described. The inspector said there was no history, or the ECU is not getting any data? My understanding is the testers are looking for a minimum number of start/stop cycles in the memory. If, for instance, you disconnected the battery long enough to clear all codes due to an intermittent CEL, in hopes of passing inspection before CEL popped again, they can tell you've done that by the lack of the start/stop cycles in the ECU memory. If you have had the battery disconnected to work on the car for some other reason the same situation arises, despite no effort to "game" the system. The dealer/shop guys will use a portable device, usually plugged into cig lighter, to maintain memory while the batt is disconnected.

If, in fact the ECU is receiving no sensor data, the car should not run at all.

Anyone else? Please correct me if I'm off base here.

Glenn

Jake@FAPFab · #3 03-02-2011, 05:30 PM

You are right, Glenn.

The ecu needs a good bit of driving to completely "ready" itself. So a disconnected power source erases the previous run parameters

thumper_svx · #4 03-02-2011, 06:43 PM

I called the guy again when I got off work and he told me that the problem was the "monitors weren't ready". I talked to him for a bit, and he gave me a know-it-all attitude and was a bit of a pain to talk to, but it got me thinking about doing some Googling.

A bit of research turned up this;

http://epa.gov/otaq/regs/im/obd/r01015.pdf

If you scroll down to Appendix D on page 31 the following text appears;

1996 Subaru vehicles - Vehicles will clear readiness at key-off. There is no reprogramming available for this line of vehicles. These vehicles should be scanned for MIL illumination without regard to readiness status

Very interesting piece of data for those of us with 96's. I didn't know that, and I guess the shop I used to take my old 96 to for testing did know it. However, now I get to go back there tomorrow and lecture the manager about properly educating his employees <sigh>

Thanks all for the input... I know that leaving my car off will tend to clear codes but I knew that wasn't the case. The car was stored for about 8 months, but two weeks ago I drove it almost 1000 miles in a weekend to get it back from Denver to St. Louis, and have driven it a few times since. Also, I have a really nice OBD2 tool so I don't need to do the "battery thing" to clear my codes

And yes, Rojo; if the sensors aren't providing data then typically the car will not start. I know that from the pain I had with replacing sensors I thought were bad in my last 96

RojoRocket · #5 03-02-2011, 07:04 PM

Now that's enough to piss you off!!

Sorry Thumper, I wasn't trying to be a smartass, just sharing what I thought to be true. Had no idea the 96's were such a different beast. I've had my 97 in for test twice now with no problem. I read that you had an OBDII tool, so understood you could clear codes without using the battery disconnect process.
Good luck with the shop guy!

Glenn

thumper_svx · #6 03-03-2011, 05:52 AM

Hey Rojo... no worries! Sorry if I seemed pissed off, in part it was probably because of dealing with the idiot at the shop. Now I get to go "educate" them before I head to work. Lovely.

Seriously, this forum and others like it are for sharing information. You shared... and that's awesome. We all need help to keep these beasties on the road as long as possible, and it's advice like yours that DOES indeed help.

Thanks again