Recently I had some issues with my car... CEL comes on for 02 sensors so I replaced the 2 in the Y pipe. Afterwards I cleared the ECU and the infamous Knock Sensor code came up... I changed the knock sensor last week. Next day CEL comes up again... Knock sensor, rear 02 in the cat, MAP sensor and Crank sensor... what a bastard! Yesterday I changed the 02 in the cat figuring that it was tripping the knock sensor as well.... I cleared the ECU and guess what happened this morning... again with the CEL. This time Knock Sensor, rear 02 in the cat.. both again as well as Map sensor and EGR.. out of nowhere... I dont know what to do anymore... I'm tired of this BS...

I checked the fuse for the 02 and it was fine... I dont know what else it could be... any help?

 

Check the ground on the rear cat o2. Clean the crank sensor and see if that CEL goes away.

 

Maybe your ECU is starting to get stupid.... do you have any driveabilty problems or bad mileage.

 

I agree about that little ground wire.

 

Where is the ground?

 

Let me go look........

 

I believe it is in the front of the cat. Also clean hte ground points on the LOWER IM.

 

I don't think that ground strap by the cat matters.... mine has been hangin down for over a year with no codes.

 

The wire comes off the top bolt of the hanger on the drivers side on mine, it is supposed to connect to the exhaust somewhere in from of the cat, any where would be ok I imagine. Just clip it somewhere or wedge it between some metal hardware.

 

That ground has been hanging since I busted my flex section and the muffler guy decided to cut it for some reason... he said it didnt matter but I guess I'll try to put it on tomorrow... I'm really really confused here on what to do...

 

My guess is that the ground by the cat is not important UNTIL other grounds somehow get disconnected thru age and wear and tear. I gotta believe Nissan put it there for a reason. A bad ground is like a bad fuse. I had different codes coming up until I fixed that wire.

Hope I helped.

 

That ground wire by the cat is a chassis ground and has nothing to do with the engine control system (ECS).

The three-wire rear O2 sensor does not have a built-in signal ground conductor like the 4-wire sensors used on 98 and up. A separate wire on ecu pin 112 is run to engine grounds F18 and F19 (intake manifold collector) for the rear O2 signal ground.
These two grounds are used by the majority of the ECS sensors.

In general, multiple sensors failing simultaneously is a pretty rare occurance.

I would check the integrity of the two engine grounds along with any connectors between them and the ecu connector.

 

Alright went out this morning and connected the ground back... but to no avail

I got rid of the EGR code but I still have knock sensor, rear 02 and Map sensor...

I pretty much know that the 02 is tripping the knock sensor so theres something wrong with it.. but what? I doubt the MAP sensor would trigger the other 2. What could it be?

 

Maybe hte rear o2 is bad, it should have a warrenty. Replace it. How much is hte Map sensor?

 

hey at least your battery is fine.....

 

just reset your ecu by unplugging the battery for 20 min, drive it for few hundred miles, and if it comes back then you have a problem but other wise i had same codes, reset and it went away. check using a voltmeter on the connectors o nthe sensors to make sure they are up to spec

 

The rear O2 sensor that you replaced. Was it OEM or aftermarket?

There are two different types of three-wire O2 sensors available (zirconia & titania)
95%+ of the automotive world uses zirconia. Nissan for whatever reason chose titania for the rear sensor in 96 & 97.

They have different voltage output ranges and are not interchangeable.

 

I've reset my ECU about a dozen times and it comes back within a few minutes after turning the car off and back on


The rear 02 was aftermarket... it was pretty much OEM though it was made by the same company believe it or not.

I was reading on the FSM the following..

like eng92 said, its made of ceramic titania...

Malfunction detected when:
An excessively high voltage from the sensor is sent to ECM... Check items.. Harness or connectors and rear heated oxygen sensor... which is the sensor itself.

OR other malfuctions

The maximum and minimum voltages from the sensor are not reached to the specified voltages
It takes more time for the sensor to respond between rich and lean than the specified time.

Check items
Harness or connectors... the sensor circuit is open
rear heated oxygen sensor
fuel pressure
injectors
intake air leaks

 

maybe something with your ecu or harness or connection?? when i reset the ecu it should take at least some time for the codes to come up... not entirely sure on this but maybe try swaping out ecu with a buddy?

 

Do you have the mfr and p/n for the O2 sensor you used?
Was it a universal type where you had to splice into the stock wires or oem type with the correct connector?

If you have a sensitive digital meter available with long enough leads, you can verify the integrity of the two intake collector engine grounds referenced to ecu harness terminal 112 (unplug connector from ecu before checking)

If your leads are not long enough, then just measure the resistance between ecu pins 112 and 116 (harness side with connector disconnected from the ecu)

 

goodhead... nah the codes come right back up... if I clear the codes and turn the car on for a few minutes they wont come on... but once I turn the car off and turn it back on.. boom the light comes right on

eng92... the 02 was by a brand called Standard... the 02 itself was stamped with 3 letters.. not NGK but somethign similar and I believe it said Japan on it... It was OEM type which plugged in and had the clip and pastic cover just like OEM... actually it looked exactly like OEM. I was hoping on buying a digital meter, I dont think I have much of a choice. I went back out and pulled the 02 out and ran the car without it... hoping it would maybe clear something stuck in there... but nothing.... THe MAP sensor I believe is about $100... I'm not really worried about it right now. I have diagrams Kevlo sent me so I can take it out and fiddle with it and see if it is clogged. However the 02 has me completely stumped

by the way I really appreciate it... thank you guys

 

If you know someone who has an OBD-II scanner, you can use that to monitor the O2 sensor output (sensor 2 bank 2).

Once the engine has warmed up, the voltage will fluctuate between 0 and 2 volts. If it stays at 0 V and does not fluctuate, either the sensor is bad or you have a bad ground between the ecu and the engine.

 

hey ANT what happened to your car???

here's a shady fix:

if it's the rear heated o2 sensor, how about getting one of those simulated o2 black boxes?

that way you get wrid of the sensor alltogether and see if it's something else causing the CEL to pop up.

sounds to me like sensor is not wired properly, if it comes on immediately after starting the car the 2nd time. I have a faulty o2 sensor and CEL usually comes on 30 mins after i start the car the 2nd time.

 

I'm guessing theres some kind of connection that isnt there. How else would the light come on right afterwards... it seems to me as if the ECU is reading a completely dead 02...

A buddy of mine has the Snap On diagnostic machine at his shop so I'll drop by his place this weekend and find out for sure.

 

I assume you have the OEM o2 sensors? My guess is you use the ODBII reader and run a test on it. I have the "AutoEnginuity" Which connects to my Laptop then the ODBII connector, it gives me whole buhch of reading for the O2 sensors. I can run a test on each O2 sensors. It could be Possible that you have bad O2 sensor the one you purchased. Or all together I can be wrong. But Give that a try ODBII try to clear the code that way.