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try swapping the car with a good known one
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Posted by Siegfried (more from Siegfried) on Wed, 24 Jul 2013 10:54:42 Share Post by Email
In Reply to: Re: ECU = Electronic Control Unit, Sunset Park, Wed, 24 Jul 2013 09:20:03
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if the problem is gone, then it was the car which was giving troubles. Otherwise it was the driver.

SP,
LH ECU needs good ground, 15 and 30 lines connections in order to operate. To toggle on the fuel pump relay (ECU pin #20 for LH ver. 2.4) it needs a live RPM input signal on pin #1. In your case RPM comes from EZK ECU, pin #17.
To start driving injectors, LH ECU also needs either a live signal from AMM (air-mass meter) or its absolute absence (limp-home mode). If your AMM is half-way dead (or half-way alive, should you be of more optimistic nature), then your LH ECU may still rely on it as a live data source and thus give you troubles (e.g. a too weak AMM signal may tell LH ECU that you're not starting your baby, but instead doing the engine-braking when all injectors are to be closed)
The EZK ECU needs CPS (crank-shaft position sensor) signal on pin 24 in order to start sending RPM signal to other devices like tachometer and LH ECU. And for appropriate ignition advance it need Tq signal from LH ECU on pin #8.

You can use voltmeter or multimeter to check for 12V on 15 and 30 lines and on fuel relay pins (*). AMM signal can be roughly checked with a voltmeter/multimeter, but just like RPM, CPS and Tq signals it is better to use an oscilloscope (a cheap USB oscilloscope for $100 off the Bay will work fine). A quick check for RPM/CPS/injector signal can be done with a led tester pen. Tq signal really needs an oscilloscope - and a good one.

Just do not forget to check it only under load: you must not disconnect or disassemble any connectors. You might want using some small needles to brake thru the insulation into the wires.

Zig

(*)
Fuel and system relays, injectors, idle valve - they all are driven by negative signals. It means that they have a constant +12V supply (thru 15 line or system relay) and LH ECU sends them 0 (negative) signal when it wants them to be on. When it doesn't want them to be on, it sends them nothing and so there's no current going thru them - they're off.
So you've got to check both sides - whether it get's +12V (put one tester lead on the negative battery terminal or another good ground like intake manifold and another one onto/into the terminal/wire) and if it gets that very negative signal (one tester lead goes onto a good 12V source like battery positive terminal and the other lead checks the subject).

posted by 188.134.4...
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