ecm malfunction

[DONDIDIT]

i have a grand am se 96
when they hook the scanner up to my car
i wont read anything.. the screen just stays black
and i have to pass the emissions test of my liscense will be suspended
ive sent it to two places.. and both say the same thing..

anyone know what causes this??

thanx for all you help in advance

[rixGAphx]

It's a 'PCM' for us.

The PCM will always report out to the world what it knows and senses.
But, the wires between the PCM and the OBD-II port may have been damaged, especially if somebody did some work under the dash.

Look in that area for damage; even a crimp or single damaged wire in the harness will result in no connection at the port.

I *think* every state that does emissions testing has a special procedure for dealing with non-downloading OBD-II's.
They do an extra-careful visual inspection of gas cap, cat, etc. and do a more detailed sniffer test.
Check with your state's website and see if there's a special place to go for this special exam.

Good luck.
-Rick

[DONDIDIT]

thanx rixGAphx
i just spoke to the lady from emissions.. they basically told me.. that in order to do anything the need the OBD to report codes..

damn damn damn
and i checked for pinched wires n stuff.. i found nothing unusual.. i popped off the casing on both sides under the dash..

i think i have the problem at least down to two things..
the check engine and ets light are on because of the back O2 sensor.. and the obd system wont send out codes..

haha.. so i guess i should take it to a shop and let em rape my pockets huh?

thanx again for all the help and anymore suggestions are more than welcome..
ill keep you posted..

[rixGAphx]

Hold on, while I ponder this new info.

May take an hour or so, since the boss somehow thinks I'm supposed to be productive on HIS work when I'm being paid by HIS dime :roll2:

-Rick

[rixGAphx]

OK, and comparing this to the info in the other thread (Old Guys) where you said the O2 sensor was replaced, seemed to solve the problem; problem returned, 'SES' light came 'on'.

WHICH 'O2 Sensor' was already replaced, and what code was displayed (a 'P0xxx' number) that lead to that diagnosis?
Just trying to re-discover old knowledge here, since we don't have access to the OBD-II at this point).

Still pondering, and standing-by.
-Rick

[2K SE]

ETS light will not light for a bad o2 sesnsor. That's telling you the Traction control system has a prob. And I think the o2 sensor could be a backyard job. I haven't done it, yet, but that could save you bucks and someone will tell us (I hope) if it's a big job or not. The ETS light should not cause you to fail the emissions test.

[rixGAphx]

I agree with 2K that ETS is not in the current OBD-II/rough-engine scenario.
But I appreciate you telling us even peripheral info.
* * *
It’s doubtful to me that your two main problems (no OBD-II connectivity, and lousy-running engine) are related.

But there is one strong inter-related possibility:
Bad electrical power to the PCM.
GA’s are notorious for doing marvelously-stoopid stuff when the power from the battery isn’t getting through properly.
My thinking is that the PCM is getting good power (or it wouldn’t run) but the sensors (and scanner) aren’t getting adequate ground. So:
1. Make CERTAIN your battery cables and connections are tight and shiny brite. Cut the molded rubber boots off the factory cable ends, and inspect/clean/replace as required.
2. The ground from the battery has a thick cable to the engine block, and a thinner wire to the fenderwall. Check both ends, and re-make as necessary for good, clean and tight connection.
3. Finally, at the PCM behind the passenger kickpanel, there should be a separate wire from the PCM to its ground terminal. Remake this ground, by scrapping paint from a nearby metal body surface and drilling a small hole; screw the ground cable directly to the body.

Since all the above is cheap, necessary (or at least of possible benefit), not at all harmful, and relatively easy, I would perform it before going to a shop.

Doing some more pondering.
-Rick

[DONDIDIT]

ok cool--- so im gonna go check all my cables--- n stuff.. that should be too much trouble at all..

i dont remember the codes and i lost the reciept but when i had it last tested bout 4 months ago.. it said both my o2 sensors were bad.. the guy at autozone told me to just try replacing the front and that should fix it.. i replaced it and both lights went off for a couple days.. then they came right back on shiney n bright..

check this out.. its about the ets and check engine light




ets check engine light (http://www.automotivehelper.com/topic143364.htm)

[rixGAphx]

Checked out that thread.

Nobody ever did make a connection between the two conditions (O2 and ETS).

ETS problems are their own little subset, and relatively-easy to diagnose.
Because the ETS is the ONE system that connects to all three control modules [(PCM, for engine and tranny), BCM-Body Control Module (for lighting/snsor of the brakehandle position) and ABS (for speed sensing)], any problem with any of the modules may trigger a fault in the ETS.
Omce the base problem is discovered, the ETS *usually* returns to normal operation.

In any case, trying to solve it, while the other problems are overwhelming, is fruitless.
It's more productive to ignore the damned thing for the moment.
* * * *
Now, back to your main two problems:

The front O2 sensor is new; the rear O2 sensor was telling AutoZone 4 months ago that there was something wrong there, but the old one is still in place.

Buy a bottle of name-brand off-the-shelf fuel injector cleaner, and run it thru the tank.
There's a strong possibility that one (or more) of your injectors is sticking open (because of crud in the orifice) and allowing that injector to spray lots of extra fuel. The result is very-rich exhaust (in addition to the other three cylinders spraying 'rich cause the PCM is in 'open-loop').
This has:
1. Almost-certainly contaminated/ruined the new front O2 sensor;
2. *Prolly* nailed the coffin shut on the old rear O2 sensor; and,
3. Possibly ruined the catalytic converter, as it was unable to burn all the crap out of the super-rich exhaust.

Pull all the plugs, and see if one of them shows signs of fouling/rich burning.
If so, maybe just replace the injector to that cylinder, since it's the one that's sticking open.
A very-rich cylinder will cause a P030x code, where 'x' is the offending cylinder, which was the problem of one of the discussee's on the other board's thread.
* * * *
Here are some other thoughts on your condition, in no particular order:
The front O2 sensor is used to adjust the FI for optimum mixture (not too lean, not too rich).

The rear O2 sensor gives signals to the PCM, but the PCM doesn't use them for adjusting the FI mixture.
Rather, the PCM compares the values of the two O2 sensors, and determines if the catalytic converter is working properly (if the values are nearly the same, that means the cat isn't doing it's job so the PCM tells you that).
It's almost impossible for the PCM to know if the rear O2 sensor is bad, since it doesn't have anything to reference against.
BUT, the rear sensor has a heating circuit that can fail, and the PCM will tell you that so you can replace the sensor (or fix the wire; remeber, the codes areNOT telling you a sensor is bad; rather, they tell you that a sensor CIRCUIT has a problem).

Even if you replace a rear O2 sensor, it will have very little affect on the engine's performance (since it doesn't affect the PCM's decisions much, if any).
Conversely, if the engine is running rough, changing the rear O2 sensor won't do a thing to improve the condition.

So, your problem is somewhere else.

IF the problem were simply with the PCM or the connection, the PCM would default to 'open-loop', limp-home operation. Very rich, down on hp, down on mpg, but smooth and dependable operation to get you to a mechanic.

Since this isn't your condition, something else is wrong.
Could be ignition (like one of the coils) or FI (like a failed or stuck injector).

I think your engine's problem is NOT related to the lack of reporting by the OBD, and vice-versa.
I think there are two different problems, and getting an OBD-II reading is the most important (since that will prolly help answer the other problem).

Good luck.
-Rick

[DONDIDIT]

mannnnnn...
thas some good stuff right there..

makes alot more sense than what i was thinking..
so i guess i gotta take it step by step---
ill be posting back in this same thread in a couple of days and let you know what happens..

but man thanx rick.. your a life saver.. im sure this isnt the first time youve heard it..

my best regards
dondidit

[voyager]

i had a similar situation with my '95 some time back - the car was running obviously rich, but scanned as running lean, and then mysteriously stopped receiving signals from the ECM (PCM). after clearing the codes and trying to scan again, the PCM said everything was just fine but the car still had all the symptoms as before... then the PCM stopped responding again and the car remained in 'limp-home mode'

my car only has one O2 sensor, (it's OBDI.5) on the manifold, which was destroyed by the rich exhaust.. it and the PCM were replaced in my backyard, did an idle relearn, got out of limp home mode but still had rich exhaust, bad idle, and lean codes on the PCM.

the problem was eventually tracked down to a bad TB gasket which had a leak on the underside of the TB - never noticed it looking for vacuum leaks because of it's position.. =/
..... only found it because it was the only thing on the motor that had been touched in the months prior to the symptoms, and no other line of diagnosis was getting me anywhere. replaced the TB gasket, relearned the idle, and voila! no more problems.

my story might not be of any use to you, but i did have a fried PCM as near as i can tell..