Kigol

It would be really really awesome if someone could answer this question. I've spent countless hours over several months and talked to many people with no real conclusion. I've done my best to fully describe the issue for you below.

Car: 1996 Honda Del Sol Si
Original Engine: D16z6 (already swapped from the y8 few years ago)
Swapped Engine: D15B (JDM)
Trouble Code: P0117 "Engine Coolant Temperature (ECT) Circuit Low Input"

I was told by the shop who sold me the motor that it was OBDII. With a few fabrication exceptions common for a JDM swap, everything switched out perfectly. All harnesses plugged in and the motor turned over and currently runs and drives. But I have a check engine light on. The car runs like crap. Revs top out at 6k, poor fuel economy, high idle. I can attribute all these things to a bad ECT reading by the PCM as temperature controls fuel trim, but could it also be from the wrong/faulty PCM?

After doing extensive research on how this circuit works and how to diagnose it, I have determined that the circuit and sensor are intact. We have a scanner and the live datastream is showing a constant temperature of 215 degress C. It never moves from there no matter what the temperature of the motor is. I know the sensor works because I removed it and tested resistance in both hot and cold conditions and watched resistance change. I even put another one I had laying around in and still no good. I bridged the two pins on the sensor connector and still nothing.

When measuring resistance from the pin on the PCM and dropping to ground, I get the proper ohms on the ECT sensor and can watch it fluctuate with engine temperature. I also get .5V on the circuit which is what is supposed to be there. This tells me the circuit is ok. The only component left in the equation is the PCM itself. Could it be bad? It's strange how the only code it is throwing is this one. Am I using the wrong PCM altogether?


So if anyone can help, please do so. If you are local to NJ feel free to stop by and take a look. I will buy you dinner and all the drinks you want. This is not my first engine swap and my co-worker on the project is a master tech and both of us are at a loss. I greatly appreciate ANY insight. Thanks all.

b18cKoupe

gimme your email address, I have a honda module on the ect that is about 8 pages long . Should help you get it figured out and its easier than me explaining it to you. Also since you seem to have access to some decent tools have your master tech friend use a dso and watch the voltage on the sensor as the car warms up. Youll see the procedure in the module.

Kigol

Hi, I sent you a PM with my email address. Thank you very much, I hope it will help.. May I ask what is a diso? I use a multimeter to measure voltage and when cold it's around .5V which is about right. It should shoot up to 4V when the engine warms up and it slowly begins to increase but I don't leave it running long enough to get it there. I'll take another look later.

b18cKoupe

I sent it to you, a dso is a digital storage oscilliscope. It samples the circuit many more times per second than a regular dmm and can catch momentary dropouts that will not be detected with other tools. If your buddy works at a shop that has a real scanner like a mastertech it has a built in dso. I have a mastertech(honda pgm tester) and id help you out but I still need to buy the diagnostic leads so im waiting for them to come up on ebay,since they cost a grip to buy from vetronix.

Kigol

Awesome thank I really appreciate that. Ah yea they have a scope at the shop. I'll see if we can drop in and use it. The scanner we were using is his home use tool, a handheld that has chip keys for cars. It's fancy but I don't think it has a scope. Ill do one more test with a different meter and see if we can use his shop.

Meanwhile if anyone has other suggestions feel free. Thx

Kigol

Thanks again for the paper. Here are the updates:

-Swapped out PCM for another D16 PCM, nothing changed

-Swapped out ECT sensor for another working sensor, nothing changed

-Grounded sensor straight to chassis/battery to bypass wire harness, nothing changed.

-Ran wire straight off sensor to correcsponding pin on PCM to bypass wire harness, nothing changed

-Tested voltage at operating temperature and got a reading of ~.35v, which is lower than the spec'd range of .5v-.6v

At this point the only theory I have is that the coolant is bad. Two hoses were crossed on install and we accidentally ran fuel through the coolant system (I know I know it sucked.) We did a flush, however I'm starting to think we may need a few more. If the voltage is dropping lower than spec, that means the resistance is dropping much too far which could be caused by excessive heating. This could happen if there is a fluid in the system which could get hotter than coolant, mainly straight gas.

This is all theory and I'm just throwing darts at this point. I'd like to hear someone's take on it. So, am I stretching too much? Thanks again.

Kigol

bump

Kigol

anyone at all? starting to seem this is the problem that can't be solved. =(