Hey guys, ive replaced my ECT sensor twice, and that has to be whats wrong with my car. The CEL code is still on, even after replacing it. Is it supposed to go off after the fix? Or am I supposed to reset my ecu? Im scared to reset my ecu because it wont start without some throttle 99% of the time, and people say after its reset to use no throttle until warmed up. And yes, I have searched a lot on this subject but to no avail.

Also, the ECT wiring, which wire is the ground? Will try testing grounds if informed on which wire it is.

 

What CEL codes are you getting beside ECT, and you replaced sensor but did you check wiring also reset ecu just unplug negative on battery for about 1 min should be fine

 

Just code 6. I'm retesting the volts and stuff tonight. Does anyone know which is ground? And you're sure if I unplug the negative it will be fine?

 

What kind of car and OBD is it? I need that information to help you if it is obd1 GREEN/WHITE wire on ECT is ground and goes to D22 on ecu plug, google search ecu pinouts and wiring diagram and should help you out that's what I go by

 

You need to reset the ECU or the code will still be stored in memory, as far as not touching the throttle on first start thats just a best practice example, so the ECU can "relearn" everything I would reset the ECU and check for codes again after 30 mins, if the code keeps popping up next thing to verify is proper wiring

to reset ecu unhook a bettery terminal positive or neg for a few mins then hook back up and start the car, let idle for 15 or 20 mins

 

****, sorry guys. I forgot to say my car is a boosted b18b1 in a 93 hatch SI. Ill have to check when I get home but im pretty sure my car is obd 2.

 

id start with looking for brraks in the wiring

 

Car is OBD1, Green/WHITE wire on plug is ground the other one is signal, reset ecu by removing Negative on battery for 1 minute

 

Which ground do i test? D13 is the ECT sensor and D22 is just sensor ground.

This is the ECT ground which is red and white. (D13)



This is the sensor ground (D22)



Either way i tested the ground on both but didnt get anything. But im planning on running a ground from the CORRECT pin (D13 or D22) to the sensor plug on the outside of the car to see if that remedies my issue.

 

check continuity from the harness to the sensor itself

 

The plug to the sensor?

 

yes. should have very low resistance, continuity, from ecu plug to sensor plug. signal wire should have no continuity to chassis ground or ground wire, and ground wire should have continuity to chassis ground as long as the engine harness is properly grounded. (perform these tests with the sensor unplugged of course).
if the above passes, or you find an issue and fix it, you can then run the next test of testing resistance across the two terminals of the sensor itsself, comparing to stock specs (I forget the specs), but then plugging the sensor in and checking resistance between both terminals at the ecu plug which should give nearly identical readings if all is well.

and your rough starting issue is because of the ect sensor issue. once the issue is fixed, it should start normally, assuming the tune is decent. once the issue is solved, the code does need to be cleared for everything to go back to normal.

 

Which one do I test for continuity, D13 or D22? I tested both to the sensor plug last night and didn't get a reading. That's the thing I need to know, which plug because I will run a ground from the harness to the plug (out side of the car with a long wire) and see if it runs correctly. I want to make sure I am using the right pinout on the harness so I don't fry sh*t up. This is just for diagnoses right now then will run a ground correctly. Please someone tell me which one.

 

I went back and checked the wiring diagram to make sure.

d13 is the signal wire and should have continuity between d13 at the ecu (red/white) and the red/white wire at the sensor plug, and should not have continuity to ground.

d22 is sensor ground, which is shared with several other sensors like the tps, map sensor, iat sensor, etc. d22 (green/white) should have continuity to the green/white or green/blue wire at the ect sensor plug AND continuity to chassis/engine ground. it should also have continuity to the same color wire on the tps and map sensor and iat sensor.

attached is a pic of the pinout location, obd1

.

 

in the first pic, the plug is actually labelled wrong haha. C = D in the first pic for the obd1 plugs

 

Thank you so much dude. This is exactly the answer I was looking for. I will test the continuity again tonight. How would I rewire a ground? Not the smartest person when it comes to electrical lol.

Edit: I will also test continuity from D22 to the map and see if I have continuity there as well. If I do, then its broke somewhere after the map ground.

 

I personally love electrical stuff, and honestly it's easier than most think, especially with hondas.
if the above testing does not pass perfectly, I would unplug the engine harness, and test continuity between the sensor plug and engine harness plugs, then test continuity from the engine harness plugs to the ecu plug. find which side of the harness has the break or short, the start opening up the harness and find the actual damage and repair as necessary. external wires and unprotected wires are never a good idea. maybe you'll get lucky and find some stupid issue.
I recently had a problem with my lowbeams not working, diagnosed it to be a break in the main power wire somewhere between the relay and the headlights. I ripped my entire front end off, took almost the entire chassis harness apart just to chase the wire, only to find out is was a bad connection between two plugs inside the car. taped the harness back up, assembled the front end, pushed the plug together and apart a couple times, added some dielectric grease and good to go.

when testing for continuity, don't use a test light. use a multimeter/ohmmeter, set to the lowest setting. ideally it should have 0.5ohms or less if continuity exists. more than 1 ohm means it still has a connection, but a very weak connection. infinite resistance means a break in the wiring or a really bad connection somewhere between plugs.

 

Thanks man. Yes, I am using a multimeter. So if the ECT ground from the harness to the sensor plug doesn't pass, try the ecu to harness? The more I think about it the more I bet its a broken or exposed wire. Will keep this thread updated.

 

Well guys I found my problem. My IAT and TPS are coming back with continuity and my map and ect arent. I guess it's time to find the break in the line. Any ideas where?

 

somewhere in the wiring

on a serious note; what isn't getting continuity? the signal wires or the ground wires?

 

The grounds on the map and ect. The signal wire isn't getting continuity on the ect either but I didn't put much time into checking that. The tps and iat are getting continuity, but the map and ect arent. I tripled checked everything. How are the grounds setup? Is it one sensor ground wire and it just splits into a bunch of sensors? Because that would give me insight where the breaks are.

 

I believe there are two actual main sensor ground wires, with multiple junctions in each wire. all of them eventually lead to pins d21 and d22 and the harness ground on or near the water outlet.

 

So how do You suggest I find them? Tear my intake manifold off? That's where the bulk of the harness is at.

 

you should be able to remove the entire engine harness without taking any engine parts off.
also, the o2 ground is also tied in with the same grounds as above.

first thing I would do though before removing anything is unplug the engine harness from the chassis harness as I mentioned above, and test continuity from all the sensor grounds to the pin[s] at the end of the harness. I don't know the pinout, but it should be the only 1 or 2 pins with a green/white wire. this will tell you if the breaks are in the engine harness or the chassis harness.

if it is in fact an issue with the engine harness, yes I would suggest taking the engine harness off the engine and removing the tape and casing, and chasing the ground wires to find the break. the junctions will be obvious. doesn't take a rocket surgeon to figure it out once you dive into it. its really pretty straightforward. and bonus, when you put the casing back on just use new electrical tape (3M ONLY!), it'll look like new again. have a good hand cleaner on tap though, taking the old tape and casing off can be messy and will get your hands all sorts of nasty that regular soap will not take off

 

Sorry if I sound like an idiot lol. Such a noob to electrical.

The engine and chassis harness connect by the firewall on the very top on the drivers side correct? Then just test from sensor grounds to the end of the engine harness plug? Then if it has continuity there, test the chassis harness from the plug by the ecu to the end that plugs the engine harness to the chassis harness? If it's the engine harness, you can just take it out and tear into it and look for the break right?

See I thought the wiring harness was all just one piece-_-.