Ok so short story 5v (red and white wire) at the ECU 5v at the sensor on the thermo housing new ECT switch, new ECT sending unit, and new ECT sensor, new thermostat, and new coolant after a system flush. Still getting a P0118 I have good ground and continuity WHAT AM I MISSING? 1999 Honda civic EX D16y8

 

1) P0118 specifically indicates a problem in the ECT sensor circuit, so there would be no reason to replace either the ECT switch or sending unit.

2) This^ caught my attention because the ECT sensor is located below the distributor, not on the thermo housing. The 99 Y8 has 2 ECT devices on the thermo housing - the ECT switch (2P connector with a Grn wire and a Blk wire) and the FIA valve (2 vacuum hoses).

3) Is the correct ECT sensor connector (Red/Wht and Grn/Blk wires) plugged into the ECT sensor? Did you check the ECT sensor Grn/Blk wire for an open? If the latter are fine, then the ECU may be bad.

 

Today I would like to do some organized troubleshooting. Would anyone happen to know the voltage at the connectors and the ECU; also the resistance of the wires and the sensors. I know I didn't have to replace all the components but its a 2 week old build, they were still oem, and 15yrs old to my knowledge.

 

Is this thread still about P0118? If so, address these point by point:

 

The way I read a P0118 is an engine coolant temperature CURCUIT high voltage input not strictly an ECT sensor input problem. The ECU and the ECT sensor are the dominant devices in the circuit however they are not the only devices that should be considered. This is why I would like to know the voltage and resistance of all 3 devices. I have already double checked my wires against the diagram. Unfortunately the diagram does not list voltage and resistance values. Correct me if I seem to be working the problem wrong.

 

Please address (2) and (3) in my previous post point by point. The information here^ clearly contradicts information in your first post. If you fail to do so, I will lock this thread.

 

Well 2 isn't a question and as for 3 "I have already double checked my wires against the diagram." Could you now clarify how I am contradicting myself?

 

(2) points out a critical problem in your information. Address it.

You made this^ statement in your first post. Based on your own words, there appears to be a ECT sensor/switch mix up because the ECT sensor/connector is NOT located on the thermostat housing and the ECT switch/connector should have 12V not 5V. The ECT sensor is located below the distributor, as I pointed out earlier. You have yet to address this glaring issue.

 

Oh I see ok so I have 5v at the ECT switch, 12v at the ECT sensor, and I haven't checked the ECT sending unit.

 

Forget the sending unit.

There's an ECT switch and ECT sensor mix up or your information is bad.

Which is it? Post some pictures so we can sort this out.

 

switch is on the thermo housing and sensor is on the head. 5v housing 12v head

 

This^ is clearly a problem.

Post some good pictures of the 2 connectors. The wires and their colors must be clearly visible.

 

Wire colors on the thermo housing are green/black and red/white. Wire colors on the head are green and black. Unsure how to post pics still.

 

You wanna just text me? I can PM you my number.

 

The two connectors are swapped. Fix this^ and hope that the connector swap did not blow the ECU.

Good luck.

 

My Haynes manual says ECT sensor is red/wht and grn/blk and that the ECT switch is grn and blk. If you are right then the thermo housing holds the sensor and the head holds the switch. opposite of what the book says. In either case I switched them and my check engine light is gone and my scan tool reads correct temp rather than -40 or +420 degrees. It still confuses me any idea or is the book just wrong? Without a doubt if I had to choose a new best friend you would be it. Thank you so much for your quick response and outside the box knowledge.

 

Look, I'm not here to debate you. Based on your own information, your ECT sensor and ECT switch connectors were swapped.

No Y8 engine has the ECT sensor on the thermo housing and the ECT switch on the block, regardless of what you are reading (or misinterpreting) in your book.

None of the information I have provided to you is outside the box. It's all clearly documented in the Honda service manual. Throw away that Haynes manual and get the real service manual.

 

10-4 thanks again.

 

You are very welcome. Glad to know the problem is now fixed.