Why does an open or shorted TS2 sensor keep the engine from running?
Other than the MPS, the TS2 sensor input is the second most significant input to the ECU in setting the mixture. An open TS2 sensor drives T451 into saturation after the Start signal is removed, causing a very rich mixture that immediately stalls the engine. A shorted TS2 sensor causes a very lean mixture that is insufficiently rich for starting, especially when the engine is cold. See the CTC section above for more details. I have measured these effects on the D-Jetronic system on my 914 2.0L, using my EFI Model 1401 Electronic Analyzer (see my D-Jetronic Testers web page for details on this tester). With the motor cold (75 to 80 deg. F), at a simulated 2500 rpm and 10 in. Hg manifold vacuum with the TPS idle switch off, the injection duration is 6.4 ms. Disconnecting the TS2 sensor increased the injection duration to a whopping 20.7 ms – more than the engine would see below freezing while at full load! No wonder it won’t start. Substituting a short for the sensor reduced the injectio
