VDO Tach Install - Lessons Learned
VDO Tach Install - Lessons Learned Installed a VDO tach on my '06 LQ9. Initially the tach was dead except a momentary blip during start-up. Searching across the boards turned up the solution of a pull-up circuit. A quick trip to Radio Shack and 99¢ later I had all the stuff to solve the problem.
I had a hard time finding a good diagram of the pull-up circuit, so I made up the attached to document what I found:
I had a hard time finding a good diagram of the pull-up circuit, so I made up the attached to document what I found:
- The critical part is a 1K-Ohm 1/4 watt resistor (Radio Shack 271-1321).
- Different articles will show different values and I picked up a couple in the 500-600 Ohm range and they ALL worked.
- As noted in a lot of posts on LS1Tech, the normative config for a Gen-III VDO install uses the conventional (Coil type) ignition settings for a 4-Cyl engine (On-Off-Off) but check with your tuner, as he may have toggled it to an 8-cyl output. (On-On-Off)
Not sure if the E38 is the same deal, but you can try some different resistors to see whether your PCM is looking for a certain value.
I saw a couple of articles that suggested a 680-Ohm value, others in the 1K range. As they were less than a buck at Radio Shack, I picked up 3-4 different resistors and got lucky with the first.
Good luck!
