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ECU Failure Diagnosis Help
Hi there, I'm not a Suzuki owner, but I have been having some difficulties with my 1996 Maxima that I suspect come down to the ECU. I found your ECU page extremely helpful, but being able to ask you a question directly might help even better.

Let me describe my issue. My car is stuck in limp home mode - cannot drive over 2500 RPMs, extremely rich fuel mixture, frequent stalling but can get from place to place at about 25 mph. My biggest problem is that I am unable to connect to the computer (OBDII of course) using my scan tool (always worked in the past). CEL is illuminated (and has been for years) but scanner reads "Link error!" Computer also will not enter the diagnostic mode using the potentiometer on the side of the ECU. Took to mechanic. Mechanic's scanner reads "No data." This is what the mechanic checked: the data plug, positive and negative terminals (good), checked to make sure the wiring from data plug to ECU goes through, checked all fuses, even replaced the fuse for the ECU.

Flying blind, mechanic still checked out the engine, which had some problems. Replaced all 6 spark plugs (which were totally dead), cleaned knock sensor (it had been reading a knock sensor code for years, which I told the mechanic about). Cleaned the EGR valve (stuck shut?), cleaned the throttle plate. Declared the MAF sensor dead but didn't change due to cost of part (I will change myself). Mechanic noted that "TP sensor voltage: .35-.65" in his "Recommended Service" section, but didn't talk to me about my TPS being bad. The reference voltage is 5 volts.

I personally removed the ECU and I don't see any visible, obvious damage on the inside. The bottom line is, what can I do to narrow down whether the ECU has failed or not? No matter what, it won't communicate with anything. Does that mean I need a new (to me) ECU, or is there something else that could be preventing the ECU from communicating?

Thanks in advance for any help you can offer.
I replaced the ECU with same model from a junk yard, fired up the car. Works amazingly. I guess in this instance, it really was the ECU. I know everybody says it's never the ECU, but it looks like it in my circumstance...
sorry it was,
can be expensive. for sure.
my be the bad caps deal on nissan too...

im happy you got it sorted to good. cheers to you !

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