Failed Inspection for 3 error codes.


JohnFrisco
08-17-2005, 09:59 AM
1) Oxygen Sensor--circuit 1
2) Speed Sensor
3) Knock Sensor

In regards to the Speed Sensor, I think this bad sensor is causing my odometer/speedometer to intermittently stop/start working. Am I correct or do you think I need to replace the speedometer? The speedometer and odometer either work together at the same time or don't work. When one of them works so does the other and visa versa.

In regards to the Knock Sensor I heard that this can be a real pain to get at and replace. Can the Oxygen Sensor be causing the knock sensor to put out a bad code?

Thanks for any input!

1996 Altima GXE

efosa
08-17-2005, 01:29 PM
Hey,
I am new to this thread stuff. I hope my little information will be of help to you.
The sensor sensor sends signal to the ecm. In the dash, one meter displays the rpm and the other diplays the mileage. These two meters get "instructions" from the ECM. If the speed sensor is not sending data to the ECM, then the ECM has no "instruction" for the rpm/mileage meters. The spedometer and the speed sensors are seperate but components of the same system.
If you have an automatic transmission, I suggest you change the speed sensor b4 you start having shift problems and many more, unless you are not driving the car.

Personally, I would change th speed sensor first before the O2 sensor or the Knock sensor.

After repacing the speed sensor, clear all the error codes from the ECM. Drive the car for a couple of miles, then check again for error codes. If the O2 sensor and the Knock Sensors are still coming up, then replace the O2 Sensor. There are about 2 or 3 O2 Sensor (i am not too certain) but if you disconnect the connections and probe the wires with a resistor, you can tell which one is at fault (low reading). Or you may consult the Haynes manual for specification for the front and rear O2 sensors.

Clear all codes again, drive for several miles and check again for error codes if the knock sensor is stil faulty, then you will have to replace it.

I suspect that the speed sensor is the cause of all your problems. But then, Nissan and other cars always have the problems of O2 sensors (high mileage). Knock sensor can fail if you use gasoline of the improper octane rating.

Let the knock sensor be the last thing you change.

JustSayGo
08-17-2005, 05:05 PM
First of all your Altima does have two O2 sensors. The rear O2 sensor is after the cat. You will find the front O2 sensor is located in the exhaust manifold. You have two circuits in the front O2 sensor with three wires. One is the heater circuit and the other sends a message to the ECU.

Speedometers are not sensors. The speedometer and odometer display the message that comes directly from the VSS (Vehicle Speed Sensor). The VSS would also affect an automatic transmission if you had one.

The tachometer measures engine RPM and uses the same signal from the CPS (crankshaft Position Sensor) that signals spark and fuel injection The CPS is located inside the distributor. The tachometer connection is made at the CPU because it is convieneint.

Your VSS is bad or the connection plug where it connects to the wire harness is not making a good connection. The VSS problem is also the cause of the speedometer-odometer problem. The VSS is in the transmission near the starter and the half-axle shaft.

If you failed emissions because of excessive Hydro-carbons, replace your 02 sensor. Remove and clean both battery cable connections and making sure they are tight when you are through. That should clear the codes and eliminate the cause possibly being from a bad ground. Check the ground cable between the engine and the body. Make sure the cable isn't loose or missing.

The VSS doesn't effect fuel mixture in a way that will make emissions excessive.

The transmission could be making so much noise that the knock sensor sends a signal to the CPU and spark timing is retarded but can't change the noise.

Bad fuel contaminates O2 sensors, but does not effect the knock sensor you will find in the engine block near the oil filter. I suspect that you may find that all three sensors are bad. All three are easy to replace once you are under the car. No doubt the VSS will test ok since the problem is intermittent. You will find the O2 sensor is contaminated from over 100,000 mi use. If you decide you need to buy the VSS, buy all three sensors online and combine shipping. You will save plenty.

JohnFrisco
08-17-2005, 05:31 PM
Your VSS(Vehicle Speed Sensor) is bad or the connection plug where it connects to the wire harness is not making a good connection. The VSS problem is also the cause of the speedometer-odometer problem. The VSS is in the transmission near the starter and the half-axle shaft. The VSS would also effect an automatic transmission if you had one.

If you failed emissions because of excessive Hydro-carbons, replace your 02 sensor. Remove and clean both battery cable connections and making sure they are tight when you are through. That should clear the codes and eliminate the cause possibly being from a bad ground. Check the ground cable between the engine and the body. Make sure the cable isn't loose or missing.

The VSS doesn't effect fuel mixture in a way that will make emissions excessive.

The transmission could be making so much noise that the knock sensor sends a signal to the CPU and spark timing is retarded but can't change the noise.

Bad fuel contaminates O2 sensors, but does not effect the knock sensor you will find in the engine block near the oil filter. I suspect that for some common reason you may find that all three sensors are bad. All three are easy to replace once you are under the car. No doubt the VSS will test ok since the problem is intermittent. You will find the O2 sensor is contaminated from over 100,000 mi use. If you decide you need to buy the VSS, buy all three sensors online and combine shipping. You will save plenty.

JustSayGo,

Thanks for all the info. My Altima is automatic and has over 150k miles. My car is not putting out bad emissions. In NJ they don't test your exhaust. They hook the computer up to your car and if any codes come up you fail. It stinks!

Any way I heard that the Knock Sensor is hard to get at. Is it under the engine intake manifold?

Can you please suggest a place online where I can buy these sensors cheaply?

Thanks again!

Frisco

JustSayGo
08-17-2005, 05:47 PM
Here's my favorite. I compare against AutoZone. http://www.rockauto.com/

The heater circuit in the O2 is burned out.

Each sensor is easy enough to change from underneath the car.

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