$EEHack Read Failure Every Time?

[steveo]

awesome thanks for that testing. you've confirmed it was definitely ignoring checksums in the last version. honestly given the drastic changes in the datastream code over the last few versions, and given then fact that I did it without a test bench or a car to try it on, i'm not surprised. glad it's fixed.

you definitely have a noisy aldl bus in that car but I wonder if it's a device that decides to keep chattering (corvettes definitely have a noisy aldl bus) i'd be curious to see if you ever find out what's up with that... if it's just a device we need to shut up, we can do that easily...

[NomakeWan]

Since I have the RPO sheets for both cars, I can say that in terms of features the only difference between the two cars electronically is that the '94 has the FX3 suspension and the 4L60E transmission. The transmission is handled by the PCM so that's not likely (right?), and the FX3 IIRC has its own communication that is separate from ALDL and has no ability to transmit serial data. Not to mention the problem existed before I knew that the FX3 module on my car had been unplugged, so I'm going to guess that's a red herring.

Both cars have passive keyless entry, automatic climate control, Bose audio, dual airbags, ABS, ASR, cruise control. The '95 has a bad alternator (it whines like a supercharger) but that doesn't seem to affect the data. The '94 has bad data even when the engine isn't running anyway.

I did go out and do testing on the grounds. Both vehicles use the OBDII-style 16-pin ALDL connector. On both vehicles, Pin 4 reads 92 ohms between pin 4 on the ALDL and the negative post of the battery. On both vehicles, Pin 5 reads a fluctuating value between 130 and 212 ohms between pin 5 of the ALDL and the negative post of the battery. This would seem to indicate to me that ground on the ALDL connector is not the issue. It could still very well be the 8192 signal wire.

On the '95, the previous owner was under the driver's side dash to replace a brake booster. He left the footwell light unplugged but otherwise it seems to all be there. On the '94 there is no real evidence that someone has been under there, but I did notice that the ALDL connectors on each car are mounted differently. On the '94 it's mounted pointing straight down, with one bolt and one plastic lug. On the '95 it's mounted on a bracket that points it towards the firewall and is held on with two bolts. I can't be sure if this was a year-to-year difference or a clue as I only have these two cars to work with.

[NomakeWan]

I apologize for the double post. I decided to try out TunerPro RT for the first time. EE_Auto.adx didn't work at all. $EE-16188051-Y-body-V3.8.adx worked perfectly...or so it seemed. It connects without issue and shows 0 errors straight through. But when you go back and look at the data, you still get a few random frames of absolute junk that the program accepted as legitimate data rather than as errors. For example, ignition voltage 19.7, engine run time 60427, knock count 18437...etc. It's clear that this is bad data, but just like EEHack used to, TunerPro RT is accepting bad frames as good for some reason.

I also tried Scan9495 v2.6.2 and it didn't want to stay connected either. It does have a verbose log generator too, so I went ahead and nabbed that. It's attached to this post. If the problem is with something on the ALDL line that won't shut up, surely there would be a way for me to listen for it and find it, right?

[steveo]

since its writing over a running datastream its hard to tell which device is misbehaving but maybe we can probe a bit. ill see what i can come up with

[steveo]

we had a conversation qutie a while ago perhaps involving kur4o where we talked about some b-body and y-body extra devices, but the only one that we deemed necessary to 'maybe' silence was the brake controller. i think at that time we had a list of potential devices on the lt1 aldl bus... can anyone help find that thread?

[kur4o]

That 94-95scan program is not configured for y-bodies at all. It tries to silence the f4 device, which is the pcm. On y-body the bus master is the CCM device with f1 id.

I think the aldl is configured with 1 bus master device that can request data from other devices. All slave devices are passive and only response to request from the bus master, when needed.

Every 1-2 seconds the bus master sends it`s ID with a broadcast ID message F0 56 [ID]
ID can be f4 or e4 pcm, f1 CCM, f9 some newer stuff.

It will be much easier for eehack to identify the bus master and than sends the shut up command to that ID.

On f-bodies and some b-bodies the traction control part of the brake module communicates with the pcm to request traction spark retard, On y-bodies it is an analog setup.

I still think it is some grounding issues or sensor noise with this particular car. Start disabling things like alternator, dashboard, pulling fuses and so on.

You can open the raw window in eehack and do some idle scan log.


Here are some random idle scan logs.

[kur4o]

doublepost

[NomakeWan]

Found the idle chatter logger thing and took some logs. Filenames are what state the car was in when the log was taken. Please let me know if there's any other test I can perform, I'll be more than happy to do whatever test is necessary to pin down this issue. :)