Monday, September 20, 2021

Project-Zero: Intake Air Temperature Issues


While zipping around in the Zero for inspections I noticed that the intake air temperature appears to be stuck at 104˚f (40˚c) with zero fluctuation.  The car is drivable but it's not an ideal situation as the ECU may adjust fueling to account for temperatures.


Connecting up to Emerald K6 ECU confirmed the ECU deferred to the default IAT value, 40˚c and a sensor fault.

  • To verify the ECU was fine I wired in a Delphi sensor/calibration.
    • Returned 78˚f with no faults. (Ambient for the evening in my garage)
  • Swapped pins around for the FoMoCo TMAP. <=== THIS WAS NOT THE PROBLEM.
    • No ECU faults but a very incorrect temperature (127.4˚f).
    • I suspect that the TMAP is broken. <=== THIS WAS THE PROBLEM.

In the process of swapping pins I went a little too hard and snapped one of the pin catches off which will require a replacement.

Next Steps

  • Plan A) (Plan A was the solution)
    • Replace the broken connector housing.
    • Replace the [potentially] broken TMAP.
      • Replacements have been sourced from RockAuto.
  • Plan B) (Plan B was not needed.)
    • Roll forward with the GM IAT sensor and source a GM 3-bar MAP sensor.
      • Split the sensor ground.
      • Has the advantage that I would absolutely know the calibration values for each sensor.


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