Reading the crank and OBDII (Camaro)

[SRavet at bangate.compaq.com]

m_mcdonald at marx.enet.dec.com Wrote:
| 
| 
| Markus Strobl <eusmsrt at exu.ericsson.se> has written:
| 
| <snip>
| 
| > Second subject: I own a '96 Camaro with the LT1. The service manual I
| > read was for a friends '95. GM did alot of changes for '96 to 
| > comply with OBDII. My owners manual says that the ECM now detects
| > misfires, and will flash the service engine light if it detects a
| > misfire. The '96 also has 4 (!) O2 sensors (dual cat), to detect
| > catcon degradation. 
| 
| > Does anyone have any info on OBDII? Ie how much can the engine be
| > modified before the ECM tilts? Can the ECM be modified, or can
| > it be fooled be changing the sensor readings? Any info appreciated.
| 
| <snip>
| 
| An excellent source of information about OBD-II (On-Board Diagnostics,
| Level II) is the rule issued by the Environmental Protection Agency
| (EPA) on August 9, 1995.  This rule has background information about
| the vehicle emission reduction requirements that led to OBD-II hardware
| and software.  It also has pointers to additional information such as
| emissions-related data that all auto manufacturers must make freely
| available to the public.  Fortunately, this emissions-related data
| contains much engine-performance-related data.

I skimmed this document, all I really got out of it was that the EPA is 
requiring manufacturers to make available to the general public all 
emmissions related repair information that they make available to their 
dealers.  (available not implying free).  It also seems to require that 
reprogramming of the ECM be allowed, and the information to accomplish that 
must be made available.  But the information can be made available 
indirectly, in the form of a device that can reprogram the ECM, without 
actually revealing how to reprogram it.  Did I miss anything?

| 
| The EPA rule has the formal title 40 CFR (Code of Federal Regulations)
| Parts 9 and 86 that appear on pages 40474 through 40498 of the Federal
| Register (Volume 60, Number 153).  Any local EPA office should have
| the rule available for reading and photocopying.  It's supposed to
| be available on the Internet by pointing your favorite browser to
| http://wais.access.gpo.gov or by telnetting to fedworld.gov and giving
| the command "/go epa" once you've registered and are at any menu.
| After issuing this command you should be able to find both the EPA
| rule and manufacturer-provided indexes to their cars' emissions-
| related data.  As a last resort, send me an e-mail request and I'll
| reply with the EPA rule as a long=180,000 byte file.

These indices are basically a list of the available service manuals, TSB, 
training kits, etc.  Each has a note attached saying to contact *whoever* 
to purchase the information.  It's presented as a list of files like this:
gmc0001.txt
gmc0002.txt
..

doing a search for "corvette" and "bulletin" results in a list of TSBs 
related to corvettes.

The training kits looked interesting, they included:

Description: Corvette CCM *3
 * Description Information
      1 = Manual
      2 = Student Workbook
      3 = Instructor's Guide
      4 = Overhead Slide Set
      5 = Binder
      6 = Student Package
      7 = Systematic Troubleshooting Poster
      8 = Complaint Description Form
      9 = ECM Inputs Exercise
     10 = ECM Outputs Exercise

Prices ranged from $10 to $25 or so.  I wonder if anyone knows what is 
really in these kits?


| 
| Another source of information is the OBD-II specifications for
| hardware and data stream messages.  The Society of Automotive Engineers
| (SAE) in Warrendale, Pennsylvania has a 1995 manual about this.  Its
| number is either HS-3500 or HS-3000.  The cost is about $65.00 (ouch!),
| but the contents are invaluable for someone who wants to interface
| his own IBM-compatible PC to his car's data stream.  Warrendale, PA
| has a 412 area code and the SAE accepts plastic.
| 
| Yes, the ECM can be temporarily overriden by electronic tools connected
| to a vehicle's OBD-II connector.  This allows technicians to perform
| various diagnostic tests.
| 
| Marll McDonald   KB1AGM
| m_mcdonald at marx.enet.dec.com
|  
| 



Steve Ravet
sravet at bangate.compaq.com
Baby you're a genius when it comes to cooking up some chili sauce...