NeCr0mStR

iTrader: (3)

So, I had a check engine code for the water thermosensor and I replaced it with a new one when I was putting it all back together, and I still have the same water thermosensor code coming up when I check the check engine codes. It may have to do with my slightly rough idle, and I was hoping someone might know how to fix the thermosensor problem.

kiker14

iTrader: (1)

did you clear the codes (disconnect negative terminal on the battery for a few minutes) and then drive around for a while before re-checking the codes?

NeCr0mStR

iTrader: (3)

Will try that and see if it helps. Thanks

NeCr0mStR

iTrader: (3)

I have to revive this thread. I had a bucking hesitation problem and found that my fuel pump resistor was bad, had blown out my engine (under the dash) fuse. Replaced the resistor and the fuse and everything was fine. I can actually feel the power the engine has (The tires break free and I slide sideways now). Now I have the bucking and hesitation again and this time I am throwing a water thermosensor check engine code. Which from what I read can cause this bucking and hesitation. I replaced the thermosensor when I put the engine back in because I had always seen this code, and figured why not it was cheap. I pulled the ECU and probed 3d and 2e to check resistance. When warm the car is at .27 kohm, I am letting it cool now to check it for at cool. I am not sure what else to check. If someone could help it would be great I am sure once I get this little hiccup fixed that I will be closer to a much more happy and stable driving car. Thank you

My ECU is n351 if it matters

I don't know if pin 2I is still something that I can probe on an s5. If it is I have tried probing it and the kohm resistance I get is super whack according to

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/hesitation-%40-wot-500265/

Post #15 on there. I don't get any voltage reading coming from it when the engine is hot and the ohm resistance is also whack. In kohm I get no reading but in 2000 ohm I get something. Also could this rust be a problem for grounding the ecu?

NeCr0mStR

iTrader: (3)

Ok, so in reading another post I had missed that I was supposed to have the ignition to the on position to check the 2I voltage and ohms. I turned the car on (it was cold) and got a 4.90 vdc reading, than I started the car and let it get to full warm and the vdc hadn't changed it was still 4.9 vdc. And still no OHM reading.

NeCr0mStR

iTrader: (3)

I found that my harness thermosensor plug is not attached properly onto the actual thermosensor and is more than likely what my problem is. I was wondering if super glue would be ok to hold the harness side clip in place inside of the plug. So that when I plug it into the thermosensor it will stay in place and make a good connection. Anyone think super glue is a bad idea?

HAILERS2

The water thermo sensor input is 2E on a series FIVE car. It's 2I on a series FOUR car.

If the engine is hot, fully hot, you should be able to backprobe the ECU plug that has 2E, and reading should be approx a half volt dc (or .4vdc to .5vdc). That's with all the plugs on the ECU and the key at least to ON or even running. The reading would be in the 2-3vdc if the engine is cold and that reading isn't a dead certain number due to *how cold is it?* thing.

Might try RTV instead of superglue if you have the time. Also make sure the contacts inside the plug don't *shove back* when the plug is installed on the sensors jack. Sometimes the contacts won't stay *locked in* the plug. IF that's the case I'd use super glue in some fashion to hold the contacts in place inside the plug.

Like you've seen, series four and five don't use the same pinnouts in the ECU plugs.

I can see how intermittent contact at the sensor could cause bucking etc. If the plug just fell off, then the ECU defaults that signal to 176*F and there should be no bucking. Just a more difficult start if the engine is stone cold.

By the way, anytime you check 2E for voltage on your series FIVE car, if the reading is 4.5 to 5vdc, then that means the circuit is open to the sensor. Either the plug fell off or one of the two contacts is pushed back or??????? Remember, all the ECU plugs have to be connected to the ECU when backprobing 2E.

NeCr0mStR

iTrader: (3)

Thanks HAILERS, I had the problem of the harness side plug contacts sinking in when I hooked the thermosensor up originally. I had cut the insulation (gray plastic) around both of the wires and had to break the black accordion insulation and held the wires in place while I plugged in the harness to the thermosensor. Luckily the wires for the harness plug will not be exposed to a lot of heat under the uim and lim. I am pretty sure after a morning of troubleshooting I am all done with the thermosensor check engine code. And with the fuel pump resistor replaced with a proper working resistor my hesitation and lack of power is gone. And I can hear that the engine is running great, no more popping or burping at idle. Smooth as butter and exhaust even smells cleaner.