Ok , I pulled the TPS connector and ran a jumper wire between the orange and green posts.
Then I pulled codes and got the following KOEO- 21,23,24 and 67
Using a dedicated ground wire from the DVM back to the neg batt post I got the following at the ECU, KOEO
4.93 volts on the dark green TP signal wire at the ECU - 47
10.67 volts on the red ECU power wire- 57
Looks like a bad ECU??????? Ouch!!
What do you guys think??
Hmm, now I am not "100%" convinced it's the EEC. If it was a fully bad EEC input/buffer, then that test wouldn't have changed the error codes.
It's still possible to have an input buffer that has damage input and overly loads down it's input. From your previous tests, that what it looks like.
Your best test is to put the TPS back in, and cut the TPS wire
near the EEC connector. See what that voltage is with the wire cut. Turn OFF The ignition, then see what that voltage is with the wire connected.
Double check that you have the correct wire by also measuring the voltage at the TPS.
If you see the TPS voltage going into the EEC going from ~0.7v with the wire cut to under 0.5v with the wire connected (and VREF was still ~4.8+V), then you have a bad buffer inside the EEC and it's time to get a new one. No choice.
FWIW: If
anyone (previous owner, clueless mechanic)
ever unplugged or plugged in the TPS connector while the ignition was on, then that damage could occur. Electronic circuits get damaged all the time and then don't fail "for a while". That "while" can be less than a second, or many years. It all depends on the damage that was done to the circuit. Also, there's the much lesser possibility that chip just normally failed that way. However, input buffers "shorting out" in
NOT a typical failure by any means (assuming that the input pin always had a good/proper input). And, for that buffer, as long as the TPS stayed connected or not connected while the ignition was on, that buffer input would be fine. Still, that doesn't mean that it "couldn't" happen.
I've argued and explained before WHY it's bad/stupid to plug and unplug sensors with the ignition on. However, since it requires physics, electrical, mechanical, materials, etc knowledge to fully understand why that's the case, people do it, see that the EEC still works, and say "they know better". Hmm, I've been doing chip and board design for over a dozen years. Yea, maybe those people without degrees and direct chip design knowledge really do know better than me.
Also, I'm sure they also know better than NASA, the DoD, and physical evidence. Here's some boring stuff:
IEEE - Electrical overstress and electrostatic discharge
Ahh, I found something readable by the public, in easy to understand language, and from a reliable source. Check out figure 7 on page 4:
http://www.3m.com/us/office/meetings/rg/pdfs/g1 basics of static electricity.pdf
For those that really care, here's a quick Google search term:
http://www.google.com/search?q=chip+latent+failures