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Discussion Starter · #1 ·
Dear community,
After the 2zz swap I was driving with a Bluetooth obd2 device to keep an eye on the parameters.
Out of nowhere when waiting at a traffic light I decided to disconnect the device, the moment I tried to go the car died.
-Relays are all fine - I do get 12V there.
-Fuel pump is OK - tested it by directly powering it with two wires.
-I don't have any power coming to the pump.(tested at the plug in the middle section leading to ECU area).


Is it worth the time to keep tracing wires cuz my guess is that the ECU is done.
What is your suggestion?
 

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Anything is possible but it's hard to see how the OBD2 circuit would cause a fault on the fuel pump circuit. If the ECU fried everytime I pulled an OBD2 reader from a running car, I would have a stack of dead ECU's about two stories high (or higher).

OBD2 device has two wires on a serial communication network coming from ECU (MPX), one wire for constant power from battery, and one wire for ground.

The fuel pump control circuit uses entirely different terminals and wiring (see the attachments). There is no overlap with the OBD2 circuits.

Does the Check Engine Light illuminate when you turn the key to the "Run" position? Can you make a connection to the ECU with a OBD2 device?

Pull the Circuit Opening Relay (COR) aka fuel pump relay in the box on the firewall in front of the transmission, and jumper its location, to supply constant power to the fuel pump. This is a check on the fuel pump circuitry independent of the ECU.

To check ECU function:

Check if terminal FC on the ECU goes to ground when you crank.

Check that STA (starter signal to ECU) gets power when you crank.

To check NE (crnakshaft position signal) you can use a scope or idiot light on the NE terminal or you can do the following checks: Use a noid light to see if there is an injector pulse when you crank. And/or check spark by pulling a ignition coil and grounding a spark plug to the valve cover. These both serve as checks of the crankshaft position sensor signal.

By the way these documents come from my version of the complete factory service manual that includes engine mechanical, transmission, body, electrical wiring diagram, and diagnostics. I make this available for download to other members who have a use for such a thing.
 

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One other thing that I would try is disconnecting the battery long enough to completely reset the ECU. I have no specific reason to believe that this would work, but it costs nothing to do, and there is a good enough chance that you will get lucky.
 

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Discussion Starter · #4 ·
One other thing that I would try is disconnecting the battery long enough to completely reset the ECU. I have no specific reason to believe that this would work, but it costs nothing to do, and there is a good enough chance that you will get lucky.
After the incident I was out of home for a week and the battery was unplugged. Sadly it didn't change the situation.
@MerryFrankster thank you for the detailed explanation. I will go back in the garage and start testing.
 
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