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It varies by market. NA vs EU vs Asia, etc. Kinda like O2-sensor which came on some versions of 300 and not others. At core of system is ECU made by Denso with Motronic software licenced from Bosch through Fujitsu.
1. Pull every fuse and measure resistance between legs. If I had penny for each time I heard, ”fuse looks Ok” but actually didn’t conduct electricity....
2. Confirm all electrical connectors are fully seated and clicked firmly into place.
At this point, I suggest following tests, roughly in sequence ECU uses:
3. scope crank-trigger waveforms. When starting, ECU blindly injects fuel. Then checks for crank-trigger for RPM signal (along with others) to fine-tune injector duration.
4. Measure resistance of TPS idle-switch signal going into ECU relative to sensor-ground (not chassis ground). There’s different fuel & ignition maps for idle vs. partial-throttle operation (per cylinder). If ECU doesn’t detect closed-throttle/idle properly, it will use improper fuel & ignition values for idle.
5. Measure ouput voltage of TPS position signal going into ECU. This is one of inputs used by ECU to calculate amount of air (load) going into engine. It then injects proper amount of fuel to match. Obviously, if ECU is tricked by improper TPS position signal, it willl inject incorrrect amount of fuel.
6. Measure MAP sensor output signal going into ECU. This is 2nd half of alpha-N -calculations to determine load on engine (amount of air being ingested at this very moment). If MAP-sensor outputs incorrect signal, ECU’s calculation will be off.
7. Voltage at fuel pump
Tricky part is you’ll have only 3-sec to take 3 measurements on each test point:
- signal before starting
- signal while running for 3-sec
- signal after engine stops
what will be helpful are signals that change between when it’s running and when it stops. Some should stay same when running vs. stalled. These various signal changes will help home in on possible problem area.
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