While trying to troubleshoot some engine problems I checked DTC's using the SES light (I have no cluster).

The light flashed DTC12, followed by 63 and 66.

66 is A/C related, explainable by the fact that I have no A/C.

DTC 63 is right O2 sensor open. I followed the helms manual and checked the O2 ckt voltage at the ECM side, it was 0.400 V. Helms says between 0.3 - 0.6 means faulty ECM.

It seems like I'd get more DTC's if my ECM was bad, is this an accurate check?

And would an error with one O2 cause my car to run as poorly as it does? It seems worse than just being stuck in open loop.

 

Is there any way to test the ECM? I can't communicate over the diagnostic line, so that's out.

Anyone willing to plug it into their car and see if it will communicate?

 

First thing I would do is swap the left and right O2s, clear the codes and see if the fault moves with the suspect O2. Yes a bad O2 will cause the car to run like crap in closed loop. Does the car run fine for the first several of min's in the morning, dead cold untill it reaces operating temp? If so I would think it is nothing more then a bad O2 sensor.

I just did a little research and what the code states is
"Right oxygen sensor was open showing a steady voltage between 0.35 and 0.55 volts for 60 seconds after the engine had been running for at least 2 minutes."

The O2 sensor should be a sweeping voltage and if it is a steady VDC then it is bad and needs to be replaced.

 

The voltage I measured was at the ECM side, with the O2 unplugged.

They are brand new O2's (not that this guarantees that they're good), but the main concern seems to be that the ECM is reading constant voltage with the O2 unplugged altogether.

The car won't really run long enough to get a 2 minute sample.

How do you clear codes with the paperclip method of diagnostic troubleshooting? Jump pin M to ground?

 

If you disconnected the O2 before checking it it will indicate the O2 is open because it is. I think you need to reconnect the O2 and check it again. Again I would still swap the left and right O2s and see whet the ECM tells you. As far as clearing codes goes I am not sure on this one as I use TTS datamaster to clear my codes.

I did find this link
http://www.corvettebuyers.com/ecm3.html
Here is what they said to do to clear the codes

"To clear the codes from memory, remove the negative battery cable for a minimum of 10 seconds. Very Important: Make absolutely certain the ignition key is turned to the off position. You run the very real risk of destroying the ECM/PCM module if you connect the battery with the ignition switch turned on.
Disconnecting the battery will clear all stored codes but it will also clear the radio button presets, clock, trip odometer, average gas mileage memory, power seat memory (if you have that option) and anything else that stores something in memory. Your ECM/PCM computer will also have to relearn your driving habits again and adjust the timing/mixture/exhaust emissions to your driving style."

 

Nope, I got the code with everything plugged in, then started following the Helms flow chart and it instructed me to unplug the right O2 and check the ECM voltage. I'll swap them just to check, though. It'll take all of 2 minutes. I can reach them from the top now with all that extra crap missing

This is interesting. I have a battery cut off switch and I'm sure at some point I've turned it off or on while the ignition switch is in the "on" position. I wonder if this might be the cause of the damage (if there is, in fact damage to my ECM). Although I'm not sure why this would matter, you either get 12V from the battery switch or 12V from the ignition switch; they're in series in my case. Perhaps it's the loss of battery ground that causes damage due to an offset between the vehicle and battery.

 

BTW, what year is your car? I can't get Datamaster to establish communication with mine (1993, ecm 16159278) and wondered if you had any tips. This would make things a lot easier.

I get the message that the ALDL is good but it's an unsupported PROM. It's the factory PROM...

 

1994 and we have differnt ECM's.

I do have a couple of tips but first a couple of questions.

1. Who's cable are youusing? AKM?Are you trying USB?, If so you may need to set the port to com port 5 or higher
2. What TTS version (Should be DM32xDA)
3. Have you tried freescan? I used the F-body as a refence and for you just use the 92-93 LT1 Camaro setting they have listed. http://www.andywhittaker.com/ecu/ecu_software.htm

 

Ok I think you have a one wire O2 is this correct?
If so What are the steps in your helms because Mine has three steps where
Step 1. Bring car to operating temp and check for closed loop
Step 2. Disconnect O2 and Short the O2 leads to gnd and check to see if VDC droped bellow .2 VDC (It does tell you what wires but they are not the same as yours)
Step 3. remove Jumper and check for VDC over . 3VDC

The reason I ask is do you have a step to jumper the O2 lead to ground and check for .2 VDC? I did not see you mention this and was just curi0os if you missed it or if it just didn't exist for the 92/93?

 

93 cars do not have a heated O2.

 

Thanks I just cross refenced the P/N while you where typing and came to the same conclusion.

 

Yes, I have that step also. However, due to the fact that I can not communicate with the ECM I can not check for the voltage with the O2 line shorted to ground. All I could do for that step was short the ECM ckt to ground and check the codes. I got the same code, 63.

I checked the cable connections and makeup. It's a cable from ALDLcable.com, but I checked the circuit diagram with others online and it's the same. It appears to be the right cable because I get two different errors - with it hooked up I get the error listed above, if I remove the power or gnd connection I get a different message, no ALDL cable found. I am using DM32xDA.

I will try the freescan program and see if it somehow works.

 

Ok,
I think you have a better then average chance it is the O2 then. Step 2 is for checking the O2 sensor and wiring if it does drop to . 2 VDC or less when you insert the short it indicates a BAD O2 or poor connection.

As far as the data logger not connecting the only thing I can think of is that some of the older ECM's require a 10K resistor between A and B to get the thing talking. If you have the correct version of TTS datamaster then it is either your cable, com port settings or a problem with the ECM. You are using a serial com port and not a USB port correct, USB is a PITA


Here are some scematics for ALDL cables including the AKM version simmilar to the one I use, keep in mind these are for the Lotus so some wires may be differnt.

My computer com 1 port is set to
Bbs 9600
Data bits 8
Parity none
Stop bits 1
flow control Xon/Xoff (None also works I beleive)

For the TTS Serial data Acuisition window (Pops up when you select record) I have Com 1 selected

http://www.andywhittaker.com/ecu/aldl_hardware_cont.htm

 

I think I'm chasing my tail here. I can clear codes and plug the O2 back in and it doesn't set 63 again (although maybe the car has to run before it sets O2 codes). Chart A2 also seems to indicate possible bad ECM as I can flash 12 but not communicate.

I need a difinitive way to see if my ECM or PROM are bad to eliminate that as the culprit.

Is anyone with a 93 and a scan tool willing to see if this thing will communicate on their car? I'll ship it out...

 

I am not using USB, I forgot to answer that. I'll double check com port settings. BTW, last week I did use a tech tool and it wouldn't communicate either.

Remember the days when you were helping me to pull the motor out of the car? Those were simpler times...

 

LOL,
simpler but this is not all that bad. You may need to start the car to reset the codes for at least two min's. Was the Tech tool a GM unit or an Autozone type? the local Auto Zone will not work with my ECM JFYI. If it ws the GM Tech I fear you may be in trouble with the ECM. Swappping the O2s if the code reapears will still help you out with the problem at hand. If you swap them and the problem stays with the ECM side and not the suspect O2 then you can rule the sensor out. Keep the faith you are close and have followed the same path I would have.

 

It was a multi-purpose tool called Pathfinder. I've used it to communicate with my module before (over the summer when I thought I had a bad opti), so I know it works. However, it is not an actual tech 1 so there may be subtle differences.

Frankly, I'd love to find that it is my ECM. $130 for a new computer is more than worth it if it makes my car run. I'm just doubtful that it's that simple. And to spend the money and have it NOT be the problem would really tick me off.

Here's how I would explain why the car is running poorly: bad O2 line keeps the car in open loop mode trying to warm up. Open loop means dump more fuel into the cylinder. 30# injectors mean dumping even more fuel than it realizes with no O2 feedback to tell the ECM to dial it back. Poor combustion and very rich fuel mixture fouls the plugs, pretty soon car won't run at all. That's why I can't run the car all the time to try different things, I'm killing spark plugs. I pull them out black and covered with gas.

So I can easily rationalize why the car won't run, but I want to be sure. If I can prove that this ECM will not communicate on someone else's car then I'll buy a new one and hope that's it. If it does, then I need to thoroughly analyze my vehicle wiring and test equipement set up. If it's not as simple as an ECM then I'm never going to be able to fix the timing issue if I can't get a data dump to analyze and send to Alvin to adjust the tune.

 

By the way, I couldn't get the freescan SW to work. It kept giving me a "not authorized" message. I poked around on the website and didn't see anything about that. Did you get that same message?

 

Free scan worked fine for me and I am starting to agree with your ECM idea since you have a scaner that used to talk and now wont, did you ever swap the O2's?
Your theory about open loop and extra fuel is 1/2 correct but the big problem is if you still have the stock tune and those 30 # injectors your injector constant is set to 24 (or 22 can't remember the 93 stock size). With the longer pulse width and the fact that you are getting no feed back to the ECM via the O2's to tell it is is stupid rich there is no way for the ECM to even atempt to correct the problem. You need the injector constant changed to a setting that will work with the 30's and that would fix your fat in open loop problem for the most part. If I where you and still had the stock injectors I would put them back in just untill you get the thing runing.

 

I wish you had a 94/95 I would ship you my spare ECM to give it a shot.