Hello Everyone!

I have a 1996 Nissan Quest that has a Check Engine light on. The engine hesitates with speed and power badly. I've exhausted all of resources, so I'm posting this question in hopes that I'll find a solution to my problem. My "boiling point" is reaching its top level and if I don't find a solution - this minivan won't be my quest much longer.

I took the quest to Autozone and Advance Auto for a "check engine" light diagnostics. They both told me the computer was reporting a knock and TPS sensor. I purchased both sensors (yes, I'm aware of the difficulty in changing the knock sensor). We'll get to that later if I need it.

So, I replaced the TPS sensor. After replacing the TPS sensor, I wanted to check the voltage of the TPS connector (just to make sure the sensor is getting voltage). As crazy as this sounds, when I connect the multimeter probes into the TPS connector, I get zero (flat line) readings. I'm inserting the positive probe of the voltmeter on the REF terminal and the negative probe into the GND terminal. I should get a reading of 5.0 volts. The odd thing is that if I connect the negative probe into the REF and the positive into the GND terminal, I get a reading of 10.7 I've double checked my work and when testing the voltage properly as described in the haynes manual, I get zero readings.

According to the haynes manual, if reference voltage is not available, I may have a open circuit to the PCM or a defective PCM. I'm assuming a PCM is the ECU, since the haynes manual does not reference anything about a ECU. If I'm wrong, please correct me.

Here's my main question, how do I test a PCM/ECU? I either have a problem with the wire harness or the PCM/ECU. I would like to play the process of elimination here. Does anyone know of a way to test the PCM/ECU without actually removing the PCM/ECU? And if so, could you please describe how to test it?

I know that a million other things could cause engine hesitations and check engine lights, but I need to rule out the possibility of having a bad/defective PCM/ECU before I can proceed with other diagnostics.

Thanks a million to anyone that can help with this,

Gabriel