GM VPW codes as tested on my 2002 GMC Sierra 5.3/4L60E. Some are imperfect and I hope to keep working on them, but they're useful enough to post. The PIDs I used were found mostly at
http://www.hptuners.com/forum/showthread.php?p=1474 and I made the codes myself.
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Transmission input and output shaft speeds. Looking at these two, you can determine your gear ratio (and therefore which gear you're in). Looking at ISS and engine RPM, you can determine your TCC slippage.
Transmission Input Shaft Speed: ISS
TXD: 6C10F122194101
RXF: 046205190691
RXD: 3010
MTH: 0001000A0190
Transmission Output Shaft Speed: OSS
TXD: 6C10F122194201
RXF: 046205190692
RXD: 3010
MTH: 0001000A0190
Problems: The last four characters in the MTH code, 0190, are the hexadecimal representation of the number 400, which has to be added to mine. I'm not sure why. By the time ISS or OSS read ~1000 they are accurate. At very low speeds they are not, and at a dead stop they read 400.
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Torque Converter Slip Speed: I called it TCS, but TSS or TCC could work for you.
TXD: 6C10F122199101
RXF: 046205190691
RXD: 3010
MTH: 0001000A0000
Problems: This code suffers from one bug: Negative slippage is displayed as 65535-abs(value)/10. So, -100 would be displayed as 6453.
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Torque Converter PWM Duty Cycle: I called it TCP but TPD or TDC or TCC might work for you.
TXD: 6C10F122197001
RXF: 046205190670
RXD: 3008
MTH: 0004000A0000
Problems: I don't think there are any.
Observations: When TCP is up, TCC slippage is up. I would have expected the opposite.
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Transmission Pressure: TP
TXD: 6C10F122199D01
RXF: 04620519069D
RXD: 3008
MTH: 000100010000
Problems: I don't think there are any. I have no way to confirm.
Observations: When TP is up, TCC slippage is down. I didn't realize that this pressure is used to adjust TCC slippage along with TCC PWM Duty Cycle. Is this the same pressure as is often called "Line Pressure" and controls how stiff the shifts are? That question is rhetorical here, I'll ask it elsewhere...
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Ignition Voltage: IV -- this shows voltage of the ignition wire in the dash, not the spark plug wires.
TXD: 6C10F122114101
RXF: 046205110641
RXD: 3008
MTH: 0001000A0000
Problems: I think it can be improved to show more accuracy. It seems to show whole numbers only.
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Requested Idle Speed: IDL
TXD: 6C10F122119201
RXF: 046205110692
RXD: 3008
MTH: 000A00010000
Problems: I don't think there are any.
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Intake Air Controller: IAC
TXD: 6C10F122117201
RXF: 046205110672
RXD: 3010
MTH: 000100010000
Problems: I don't think there are any.