The following resources have been obtained while installing VEMS on Toyota 4A-GE 16V & 20V engines.





After the previous work using pull-down resistors we moved onto the suggested 10k->12V pull-up resistors and the addition of a 220nF cap on top of C40.

Still not good, the latest trigger log shows some strange missing tooth issues:

Action to try next:

  1. Try to match the OEM pull-up of 0.6V with smaller value resitors.
  2. Try pull-down resistors as before, but with LM1815 pin5 jumpered to cause LM1815 to ignore any voltage below 200-450mV
  3. Use a seperate ground feed direct to the LM1815 chip.

Toyota 24+4 Trace:


Recorded with USB Instruments Stingray

Config & Tables

Connection Details

The Ne (24tooth) trigger is connected to Trig1, the G1 (4 tooth) trigger is connected to Trig2. The G- combined ground connects to the common grounds. Two 270Ohm resistors pull the signal down to ground.

Trigger Logs

Initial test:

Test with the Ne and G1 trigger inputs changed over Ge to primary trigger, Ne to secondary trigger - we were out of clues so we thought we'd try it...

Changing back to the correct trigger connections but removing the pull-down resistors.

A log from the bench test

The owner of the car has produced a spreadsheet to try and analyse the trigger logs:

Toyota 24+4 Distributor:


#10 is the injector signal - indicating 1 injection event every two ignition events.

Divider=02 means injection event every second ignition event. Good if you have 2 injectors hardwired in parallel. (or, even than, you can (at the cost of a few wasted cycles) do something like: h[0]=00 02 00 01 .. .. .. ..