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Old 04.07.2010, 21:53
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"It has always been said that the 1571 History code was normal. Is it possible that there is a PCM upgrade for the 97 that make the PCM to delete this code automatically? Let me tell you what I found. I have GMP/97-Y-UPD Engine Controls supplement book. Here is what it says at one of the first page of the book. Then I will go our torque codes. --“This service3 manual supplement is intended to software per campaign 97-040. The Tech 2tm scan tool identifies the current PCM software level of the vehicle you are repairing. If the PCM software is NOT updated, reprogram the PCM as necessary and use the information contained in the supplement to repair the vehicle. This supplement replaces the Engine control Section pages 6-347 through 6-1064 of the Corvette Service Manual (GPM/97-Y-3)”.-- Ok if your books are 98+ you might have that update already. But for us who have the original 3 books, that might be interesting. Some differences: In original book for code 1571: Conditions for SETTING the DTC. -Traction control has not failed -The engine speed is greater than 500 RPM for 20 seconds. -The desired torque signal is not received by the PCM for 3 seconds. In the updated version they added a category. Condition RUNNING the DTC -Traction control has not failed -The engine speed is greater than 500 RPM for 20 seconds. Conditions for SETTING the DTC. -The desired torque signal is not received by the PCM for 3 seconds. But below is what I found interesting. They have changed the conditions for Clearing the MIL\DTC. Condition for Clearing the MIL/DTC: Original version : -A History DTC clears after forty consecutive warm-up cycles, if this or any other emission warm-up cycles, if this or any other emission related diagnostic does not report any failures. -The PCM battery voltage is interrupted. -Use a scan tool in order to clear the MIL/DTC. Condition for Clearing the MIL/DTC: Updated version : -The PCM turns the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail. -A last test failed (Current DTC) clears when the diagnostic runs and does not fail. This is what I find very interesting. Why they added these 2 conditions for clearing the DTC ? If I understand correctly and this is where I’m not sure I fully understand these 2 condition but to me, it looks like these condition were added to make the DTC go away faster. Let summary, they added 2 ways of clearing the DTC quickly and automatically. If PCM is ok for 3 consecutive drive trips, it removes the DTC. Or last test fails Current DTC Clears when diagnostic runs and does not fail. This is an easy way to fix an harmless and intermittent problem. You just remove the error messages. I have programmer background and know that it can be done. Recap from start. Intermittent 1571 are normal in the 1997. They added 2 conditions to the PCM to clear this intermittent code automatically. They made the same modifications for P1644. Delivered Torque Output. So, having my PCM reprogrammed, I would doubt the previous owner did it, since the column recall is not done, could make the torque DTC to go away. Update. I had the PCM reflashed in February 2006. The 1571 is still there. The difference is that if I reset the code, it does not re-appear until I stop the engine. Before I had the PCM reprogrammed, it was reapearing a few miles after I reset it."
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