Nathan Brooks

Asked by Jun 11, 2016 at 11:15 AM about the 1998 Honda Civic EX

Question type: Maintenance & Repair

I have a 98 Honda civic ex 1.6 d16y8, when I got
the car it had one code p0118 witch is for the temp
sensor, and the 02sensor cat and 02htr monitor
was not ready. So I replaced the 02sensor drove it
for 10 20 miles then hooked it up to the obd reader
and all three of those monitors were ready, but
then I shut my car off and fired it back up read it
again and the monitors went back to not ready. If I
drive it for 10 miles they will go back to ready and
will stay ready till I shut the car off its a repeated
cycle. I got 2 days left on my 10 day inspection can
anyone help me out? I also have the temp sensor
on its way through the mail, could that be messing
with the cat and 02 monitors? Also at times when I
start my car up the check engine light will be off
and the p0118 code will not come up till I shut off
the car and start it back up.

5 Answers


P0118 1998 HONDA CIVIC - Engine Coolant Temperature Sensor 1 Circuit High Voltage..... Possible causes - Low Engine Coolant Level - Faulty Engine Coolant Temperature (ECT) sensor - Faulty Engine Coolant Thermostat - Engine Coolant Temperature (ECT) sensor harness is open or shorted - Engine Coolant Temperature (ECT) sensor electrical circuit poor connection..... First check to see if there are any coolant leaks and if the thermostat is opening, if problem is still there replace the coolant temperature sensor....P0118 1998 Honda Civic Description.... The Engine Coolant Temperature (ECT) sensor is used to detect the engine coolant temperature. The sensor modifies a voltage signal from the Engine Control Module (ECM). The modified signal returns to the ECM as the engine coolant temperature input. The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of the thermistor decreases as temperature increases.

Nathan Brooks

Thanks for the temp sensor aspect of the problem I know the wires and plug are okay for it, I will check the thermostat. But the main thing I'm trying to find out is the 02 sensor and catalyst montioners goi g from ready to not ready like how I dercribed in my question, do you have any ideas of what's going on with that?


I know the engine temperature needs to be at operating temp. and without the temperature sending unit not operating correctly, all other sensors will not operate correctly as the computer adjusts all other sensors according to what the TSU is feeding the computer. It just may be that replacing the TSU would take care of the problem.


Incorrect Info! all sensor are functional and operate fine regardless of "TSU" the computer is fully operational regardless of what a coolant temperature sensor sends or doesn't send. Lots of good engineering books and training materiel out there. Regards


Ok, a bad choice of words. Not that the other sensors would operate incorrectly, or the computer, but the computer would adjust to what it thinks the engine temp. is at. What I was trying to say is if the TSU is open or bad, it may explain why the 02 sensor is in the ready & not ready state, as between the 02 & the TSU are what is telling the computer how to adjust for the air fuel mixture.

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