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Bob6831 · Sep 14, 2006, 03:25 PM

Hi.
Was driving my 95 Honda Civic LX (115000 miles) to work this morning when the Check Engine light came on.
Car was not overheating, no obvious problem, oil level fine. Ran all day with no further problem indications, but the Check Engine light stayed on.
What is the possible problems??
Note that have noticed some loss of power in last 6 months, especially when going up a steep hill, and my gas mileage is less than a year ago. Think I got around 45 mpg then, get ~35-40 now.
Have changed plugs and air filter about 10000 miles ago.
Any help would be appreciated.
Could it possibly be the fuel injectors? Can I fix this with some kind of gas additive? Note that I normally use Mobil regular gas.
Just 1 other thing... I do have a funny clunk type sound that I believe is coming from the front end, notice when go slow and changing gears usually.
Thx.
Bob

TxGreaseMonkey · Sep 14, 2006, 04:26 PM

Your Civic has probably thrown some codes and that should tell you what is wrong. The clunk sound is probably unrelated and could be bad constant velocity joints. Normally, the front passenger side goes first. If you get this attended to right away, you might be able to repack the CV joint, replace the boot, and be on your way. Get under your car and examine the boots for any splitting. When a split develops, all of the CV joint grease is slung all over the place.

Bob6831 · Sep 15, 2006, 03:25 PM

Hi.
Checked my error codes today via pin in the connector. I got a 41 (primary oxygen sensor heater
?? ) What is this part? Does it make sense with my other descriptions? Note that I have been losing some coolant, may be a radiator leak, but has not been overheating that I can see.
Note that when I turned key on, I get 1 quick blink, did not count that as part of my 41.
Thx.
Bob

TxGreaseMonkey · Sep 15, 2006, 06:02 PM

This is the oxygen sensor, which is technically called the Heated Oxygen Sensor (HO2S). You will see it upfront on your exhaust manifold.

Disconnect the 8P connector from the HO2S. Measure resistance between terminals A and B on the HO2S. Is there 2-13 ohms? No--replace the HO2S. Yes--Check for continuity to body ground on each terminal on the HO2S. Is there continuity? Yes--replace the HO2S. No--Check for continuity between terminal A and terminals C-H individually. Is there continuity? Yes--replace the HO2S.

8P connector layout:
ABCD
EFGH

Run these tests before we go any further and let me know the results.

Bob6831 · Sep 16, 2006, 02:57 PM

Did a check under the hood, and see 1 8 pin connector near the distributor, but cannot get it to disconnect. Is this it, and is there a trick to getting it apart?
BTW, what does this do specifically, and do any of my other symptoms coincide with this part being bad?
Thx.
Bob

TxGreaseMonkey · Sep 16, 2006, 03:35 PM

That's it. Just follow the lead back from the sensor, which looks like a spark plug going into the exhaust manifold.

Take a small screwdriver and press the release on the connector's mount. Remove the connector from the mount and it will come apart. It takes some getting used to, but it's simple and ingeneous.

The oxygen sensor detects the oxygen content in the exhaust gas, and inputs the ECM. In operation, the ECM receives signals from the sensor and varies the duration during which fuel is injected. The heated oxygen sensor has an internal heater. The heater stabilizes the sensor's output. Therefore, you can see that your poor engine performance could be directly related to a failing oxygen sensor, which is not uncommon.

Should tests prove that the sensor is bad, install a new one and torque to 33 lb.-ft. after applying a pea-size amount of anti-seize compound to the sensor's lower threads. Allow rotation to spread the compound. Apply silicone dielectric grease to the new 8P connector.

Bob6831 · Sep 19, 2006, 07:24 PM

Hi.
Got a chance to re-look under hood.
I do see a device looking like a spark plug going into the very beginning of the exhaust pipe.
If this is what you are referring to, it is 4 wires coming from it, with a 4 pin connector going into a wire harness that does have a 8 wire connector further back.
Should I be looking at the closest connection which is the 4 wire one?
If so, what then are the pins you want me to check?
Thx.
Bob

TxGreaseMonkey · Sep 19, 2006, 08:19 PM

In this type of forum, this is the best I can do:

Originally Posted by txgreasemonkey

Disconnect the 8P connector from the HO2S. Measure resistance between terminals A and B on the HO2S. Is there 2-13 ohms? No--replace the HO2S. Yes--Check for continuity to body ground on each terminal on the HO2S. Is there continuity? Yes--replace the HO2S. No--Check for continuity between terminal A and terminals C-H individually. Is there continuity? Yes--replace the HO2S.

8P connector layout:
ABCD
EFGH

Why don't you just replace the sensor, since you are probably headed that direction anyhow? They cost $59.99 at Autozone, but can save you a lot of money in fuel and greatly improve performance.

Bob6831 · Sep 20, 2006, 07:02 AM

Geez... I do appreciate your help, but don't understand your answer.
The closest connector to the sensor is a 4 wire connector... hmmmm, maybe a 4 wire in - out connector is a '8 pin connector'? Educate me please.
As far as replacing a part($60) that may not be bad..? I do not want to possibly waste money like that if I can at all help it.
Thx.
Bob

TxGreaseMonkey · Sep 20, 2006, 09:02 AM

Hmmmmm, you obviously have a different engine and a different HO2S sensor. Therefore, spend the money and replace the sensor or wait for someone who's familiar with your engine to chime in with how to test your HO2S sensor. It could be a long wait.

Bob6831 · Sep 20, 2006, 10:04 AM

I don't understand your attitude. I hope you don't think I am trying to be wise. I am not. I asked a serious question about the connector, as to whether 4 wires going into the connector and 4 wires out was possibly a 8-pin connector. Maybe it was a dumb question, but I was not trying to be wise.
It is the original equipment engine on my 1995 Civic LX.
I just don't understand why you would replace a $60 part when it is not clear that it is the problem. Would I gain something by replacing this part anyway, even if it was not the cause of the 'Check Engine' light?'
Thx.

TxGreaseMonkey · Sep 20, 2006, 11:25 AM

There are five OEM engines: D15B8, D15Z1, D15Z1 (Calif.), D15B7, and D16Z6. You need someone who knows the HO2S test for your particular engine; otherwise, install a new sensor, take it to the dealer, or assume this is not the solution to your problem, in spite of the weight of evidence.

The answer to your last question is yes. You would improve your gas mileage, improve performance, and increase the life of your catalytic converter. Even without the Check Engine Light coming on, many people regularly replace HO2S sensors for the benefits cited.

Bob6831 · Sep 20, 2006, 08:29 PM

Can someone tell me what happened to all the replies I had from GreaseMonkey??

Azzamechanic · Dec 16, 2008, 05:23 AM

Hiya I know this thread was years ago but I was just interested if you ever sorted the problem out and what it was in the end?

edjrwinnt · Jun 17, 2009, 03:42 PM

I was able to change my own oxygen sensor from the instructions in this thread. Advanced Auto Parts had the sensor for $87 and the special sensor socket for $11. I took the manifold off with four bolts to get at the sensor a little easier. Advance actually has the same sensor with a shorter chord for $7 less that will work too. The AutoZone price on the sensor was the same.

I recommend getting the special sensor socket because if your car is as old as mine you don't want to be torquing on this with a crescent wrench.

Thank you TxGreaseMonkey. You saved me over $200. The stealership wanted $300 to fix this. Now I just hope this thing will pass E-check.

nikcivic · Mar 10, 2012, 02:45 PM

I have a 1995 Civic CX 1.5 L. I replaced the original headers with slightly larger diameter. Engine light came on and code 41 given. I like the original post on here have the 4 pin connector and a 8 pin connecter by distributor (7 pins utilized)

When I check at the 4 pin I get O/L for OHMS any way I attach. When I test the 7 pin I get .3 OHMS between any combination of the 3 in a row and O/L between any combination of the 4 in a row.

What next??